Subject: Life Sciences, Microbiology Keywords: membrane remodeling; membrane biosynthesis; membrane curvature; phospholipids; inner membrane; lipid biosynthesis
Online: 25 August 2020 (10:03:25 CEST)
Membrane remodeling and phospholipid biosynthesis are normally tightly regulated to maintain the shape and function of cells. Indeed, different physiological mechanisms ensure a precise coordination between de novo phospholipid biosynthesis and modulation of membrane morphology. Interestingly, the overproduction of certain membrane proteins hijack these regulation networks, leading to the formation of impressive intracellular membrane structures in both prokaryotic and eukaryotic cells. The proteins triggering an abnormal accumulation of membrane structures inside the cells (or membrane proliferation) share two major common features: 1) they promote the formation of highly curved membrane domains and 2) they lead to an enrichment in anionic, cone-shaped phospholipids (cardiolipin or phosphatidic acid) in the newly formed membranes. Taking into account the available examples of membrane proliferation upon protein overproduction, together with the latest biochemical, biophysical and structural data, we explore the relationship between protein synthesis and membrane biogenesis. We propose a mechanism for the formation of these non-physiological intracellular membranes that shares similarities with natural inner membrane structures found in α-proteobacteria, mitochondria and some viruses-infected cells, pointing towards a conserved feature through evolution. We hope that the information discussed in this review will give a better grasp of the biophysical mechanisms behind physiological and induced intracellular membrane proliferation, and inspire new applications, either for academia (high-yield membrane protein production and nanovesicle production) or industry (biofuel production and vaccine preparation).
ARTICLE | doi:10.20944/preprints201612.0093.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: membrane bioreactor (MBR); membrane fouling; hollow fiber membrane; hydrophilicity; hydrophobicity; wastewater treatment
Online: 18 December 2016 (10:04:27 CET)
We aimed to investigate the relationship between membrane material and development of membrane fouling in a membrane bioreactor (MBR) using membranes with different pore sizes and hydrophilicities. Batch filtration tests were performed using submerged single hollow fiber membrane ultrafiltration (UF) modules with different polymeric membrane materials including cellulose acetate (CA), polyethersulfone (PES), and polyvinylidene fluoride (PVDF) with activated sludge taken from a municipal wastewater treatment plant. The three UF hollow fiber membranes were prepared by a non-solvent-induced phase separation method and had similar water permeabilities and pore sizes. The results revealed that transmembrane pressure (TMP) increased more sharply for the hydrophobic PVDF membrane than for the hydrophilic CA membrane in batch filtration tests, even when membranes with similar permeabilities and pore sizes were used. PVDF hollow fiber membranes with smaller pores had greater fouling propensity than those with larger pores. In contrast, CA hollow fiber membranes showed good mitigation of membrane fouling regardless of pore size. The results obtained in this study suggest that the surface hydrophilicity and pore size of UF membranes clearly affect the fouling properties in MBR operation when using activated sludge.
ARTICLE | doi:10.20944/preprints202108.0393.v1
Subject: Engineering, General Engineering Keywords: Membrane oscillation; shear rate; slotted structure membrane; oil water separation and membrane fouling
Online: 19 August 2021 (06:51:11 CEST)
A new method is proposed to increase rejection in microfiltration by applying membrane oscillation using a new type of microfiltration membranes with slotted pores. The oscillations applied to the membrane surface result in reducing membrane fouling and increasing separation efficiency. An exact mathematical solution of the flow in the surrounding solution outside the oscillating membrane is developed. The oscillation results in appearance of the lift velocity, which moves oil particles away from the membrane. The latter results in both reducing membrane fouling and increasing oil droplets rejection. This developed model was supported by the experimental results for oil water separation in produced water treatment. It was proven that oil droplet concentration reduced notably in the permeate due to the membrane oscillation and that applied shear rate caused by the membrane oscillation is also reduce pore blockage. New generation of microfiltration membranes with slotted pores was used in the experiments.
ARTICLE | doi:10.20944/preprints202202.0160.v1
Subject: Life Sciences, Biochemistry Keywords: membrane pump theory; membrane potential; diffusion; Biophysics; Biology
Online: 11 February 2022 (10:27:36 CET)
The generation and maintenance of membrane potential is a fundamental part of Membrane Pump Theory. One of the key points of this hypothesis is based on a natural or facilitated molecular diffusion through several types of ion channels and pumps like the Na/K ATPase. Chemistry, physics and especially electrochemistry, however, bring strong contradictions to this theoretical assumption. By respecting the principles of chemistry and electrostatics, it becomes obvious that this theoretical hypothesis cannot work. The ionic diffusion that would be at the origin of this potential cannot take place. Indeed, the topology and the forces involved definitively exclude the current model, which must absolutely be revised according to the current state of our knowledge and allow an advance in the understanding of the phenomena and open new research perspectives.
ARTICLE | doi:10.20944/preprints201801.0091.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: turbulent flow; stirred flows; membrane fouling; membrane bioreactor
Online: 10 January 2018 (11:05:04 CET)
Numerical simulations of turbulent flows in a stirred dead-end membrane bioreactor are performed by the RNG k-ε model based on finite volume method using Fluent codes. Comparisons of numerical and experimental results confirm the reliability and feasibility of the constructed model. Flow structures such as wake flows and circulation loops in stirred flows were well simulated. An increase of stirring speed is proposed to use to minimize the low velocity region. The single vane stirrer is found to be beneficial for biological separations. Results reveal that the increase of vane number can enhance the mixing effect in flow domains. However, a circular disk stirrer goes against the formation of vertical circulations. The six-vane stirrer is found to be able to provide a uniform distribution of high shear stress.
ARTICLE | doi:10.20944/preprints201809.0242.v1
Subject: Chemistry, Chemical Engineering Keywords: Phospholipid assembly; Bicelle; Membrane fluidity; Membrane polarity; Phase behavior
Online: 13 September 2018 (14:45:35 CEST)
Self-assembly membranes, composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), were characterized at the total lipid concentration below 20 mM. The sizes of the assemblies varied depending on the molar ratio of DMPC and DHPC (q = [DMPC]/[DHPC]). The small assemblies with diameter of ca. 10 nm were formed at q ≤ 2.0 at 20 ºC (below phase transition temperature of DMPC). The physicochemical membrane properties were then studied using fluorescence probes, 1,6-diphenyl-1,3,5-hexatriene and 6-dodecanoyl-N,N-dimethyl-2-naphthylamine, upon the dilution. DHPC micelle showed a higher membrane fluidity, while the DMPC/DHPC membranes at q ≥ 0.5 showed lower membrane fluidities as well as DMPC vesicle in gel (ordered) phase. Upon dilution, the ordered membrane properties were maintained while the solution turbidities increased, implying the morphological change of the self-assembly, bicelle to the vesicle in gel phase. Based on the obtained results, a phase diagram of DMPC/DHPC binary system (at 20 ºC) is described: (i) the bicelle suspension is transparent and the membrane is in ordered state, (ii) the micelle suspension is transparent and the membrane is in disordered state, (iii) the vesicle suspension is turbid and the membrane is in ordered state.
ARTICLE | doi:10.20944/preprints201807.0112.v1
Subject: Materials Science, Surfaces, Coatings & Films Keywords: membrane distillation; polyvinylidene fluoride; copper oxide nanoparticles; membrane morphology
Online: 6 July 2018 (09:03:09 CEST)
Membrane distillation techniques appear as one of the most promise alternative to guarantee the availability of potable water in time of scarce of this essential resource. For membrane preparation, polyvinylidene fluoride (PVDF) is preferred due to the easier synthesis procedures with respect to other fluorine based polymers. In this work, copper oxide nanoparticles (CuONPs) at different weight percent (wt.%), embedded in PVDF membranes supported on non-woven polyester fabric (NWPET) were prepared by the phase-inversion method, and characterized by spectroscopy (ATR-FTIR, Raman) and electron microscopy techniques (SEM). The PVDF deposited onto the NWPET was highly composed by its polar -phase (F()= 53 %) which was determined from the ATR-FTIR spectrum. The F() value was kept constant, in the whole range of CuONPs studied (2-10 wt.%) as was determined from the ATR-FTIR spectrum. The absence of signals corresponding to CuONPs in the ATR-FTIR spectra and the appearance of peaks at 297, 360 and 630 cm-1 in the Raman spectra of the membranes suggested that the CuONPs are preferably located in the inner of the membrane but not on its surface. The membrane morphologies were characterized by SEM. From the obtained SEM micrographs, a decrease and increase in the amount of micropores and nanopores, respectively, near to the surface and intercalated in the finger-like layer were observed. As result of the CuONPs addition, the nanopores in the sponge-like layer decrease in size. The values of water contact angle (WCA) measurements showed a trend to decrease from 94° to 80° upon the addition of CuONPs (2-10 wt.%) indicating a diminish in the hydrophobicity degree of the membranes. Apparently, the increase in the amount of nanopores near to the surface decreased the membrane roughness becoming less hydrophobic.
ARTICLE | doi:10.20944/preprints201810.0321.v1
Subject: Keywords: amniotic membrane; epithelialization; inflammation; ocular surface disorders; anti-fibrotic action, amniotic membrane eye drop, amniotic membrane graft transplantation
Online: 15 October 2018 (14:35:06 CEST)
The aim of this study is to emphasize on the clinical uses of amniotic membrane (AM) in multiple ocular disorders. AM possesses many properties including promotion of epithelialization, anti-fibrotic, anti-apoptotic, anti-angiogenic properties. Epithelial wound healing on the eye surface is promoted due to several epidermal and keratocyte growth factors as well as by its anti-inflammatory and anti-scarring effects due to interleukin-10, interleukin-1 receptor antagonists and inhibition of transforming growth factor- beta (TGF-β) signal transduction by AM in the corneal and conjunctival fibroblasts respectively. It plays a crucial role by functioning as a substitute of basement membrane (BM) and as a temporary graft material. It is not only being used as an eye graft but also its extract can be used as an eye drop for corneal and external eye diseases. So its proper preparation, preservation and clinical application can bring a revolutionary change in the treatment of different ocular disorders.
Subject: Keywords: membrane theory; Association-Induction Hypothesis; ion transport, ion adsorption; membrane potential
Online: 13 August 2021 (08:53:04 CEST)
Accurate prediction of the membrane potential by membrane theory is possible on the basis that the plasma membrane is selectively permeable to ions and that permeability determines the characteristics of the membrane potential. However, an experimental and artificial cell system with an impermeable membrane serving as a model plasma membrane has a non-zero membrane potential, and this potential generated across the membrane is somehow consistent with the potential characteristics predicted by the membrane theory, despite the impermeability of the membrane to ions. A long-forgotten theory, called the association-induction hypothesis (AIH), has emerged as a more plausible mechanism for generating the membrane potential than the membrane theory to explain this unexpected behavior. The AIH asserts that ion-selective membrane permeability is not necessary for the generation of the membrane potential, which is contrary to the membrane theory. Although such an idea is not easy to accept, the experimental results clearly suggest the correctness of the AIH.
HYPOTHESIS | doi:10.20944/preprints202012.0813.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Alzheimer’s disease; beta-amyloid; protease; membrane; membrane channel; lysosome; autophagy; mitochondrion
Online: 31 December 2020 (13:32:26 CET)
Alzheimer's disease (AD) is the most common cause of dementia and affects millions of people around the world. Neuronal death in AD is initiated by the toxic action of oligomeric amyloid-β (Aβ) peptides. The formation of membrane channels by Aβ is a primary molecular action and does not require any other proteins. Channels are formed by short amyloid fragments faster and more frequently than by full-length peptides. The channel formation is dependent on an electrostatic interaction between a positively charged peptide and a negatively charged membrane. Negative membranes can be found in several locations of a cell – the inner leaflet of plasma membrane, mitochondria, and lysosomes, which all are well-known cellular targets in AD. Considering that the amyloid enters a cell by endocytosis and is exposed to lysosomal enzymes, we propose the amyloid degradation toxicity hypothesis. Endopeptidases degrade the endocytosed peptide. Produced fragments form membrane channels, which can transfer various ions (including protons) and even relatively large compounds. The neutralization of lysosomal content inactivates enzymes, which fails the whole system of recycling cellular content, including autophagy. The permeabilization of lysosomes could also lead to cell death through necrotic and apoptotic mechanisms. We discuss several mechanisms that describe how amyloid degradation products reach plasma and mitochondrial membranes, and form membrane channels. The pathogenesis of AD is discussed at various levels in a context of how the primary molecular mechanism of membrane channel formation could progress into the disease state. The discussion starts at the molecular level and extends to why the development of a disease takes years and is closely associated with aging. The proposed hypothesis offers an interpretation to several clinical observations such as the involvement of iron metabolism and an inverse association between developing Alzheimer's disease and cancer. Predictions about potential biomarkers and effectiveness of future treatments are discussed.
ARTICLE | doi:10.20944/preprints201807.0387.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: membrane fouling; membrane plasticization; nutrients transport properties; perfusion bioreactors; tissue engineering
Online: 20 July 2018 (14:01:37 CEST)
High porosity and mass transport properties of microfiltration polymeric membranes benefits nutrients supply to cells when used as scaffolds in interstitial perfusion bioreactors for tissue engineering. High nutrients transport is assumed when pore size and porosity of the membrane are in the micrometric range. The present work demonstrates that the study of membrane fouling by proteins present in the culture medium, though not done usually, should be included in the routine testing of new polymer membranes for this intended application. Two poly(ε-caprolactone) microfiltration membranes presenting similar average pore size (~0.7µm) and porosity (>80%) but different external surface porosity and pore size have been selected as case study. The present work demonstrates that a membrane with lower surface pore abundance and smaller external pore size (~0.67 µm), combined with adequate hydrodynamics and tangential flow filtration mode is usually more convenient to guarantee high flux of nutrients. On the contrary, having large external pore size (~1.70µm) and surface porosity would incur in important internal protein fouling that could not been prevented with the operation mode and hydrodynamics of the perfusion system. Additionally, the use of glycerol in the drying protocols of the membranes might cause plasticization and a consequent reduction of mass transport properties due to membrane compaction by the pressure exerted to force perfusion. Therefore, preferentially, drying protocols that omit the use of plasticizing agents are recommended.
ARTICLE | doi:10.20944/preprints201804.0078.v1
Subject: Life Sciences, Microbiology Keywords: membrane fatty acids composition; Staphylococcus aureus; staphyloxanthin; membrane fluidity; metabolic regulation
Online: 6 April 2018 (11:37:53 CEST)
Fatty acids play a major role in determining membrane biophysical properties. Staphylococcus aureus produces branched-chain fatty acids (BCFAs) and straight-chain fatty acids (SCFAs), and can incorporate exogenous SCFAs and straight-chain unsaturated fatty acids (SCUFAs). Many S. aureus strains produce the triterpenoid pigment staphyloxanthin, and the balance of BCFAs, SCFAs and staphyloxanthin determines membrane fluidity. Here, we investigated the relationship of fatty acid and carotenoid production in S. aureus using a pigmented strain (Pig1), its carotenoid-deficient mutant (Pig1ΔcrtM) and the naturally non-pigmented Staphylococcus argenteus that lacks carotenoid biosynthesis genes and is closely related to S. aureus. Fatty acid compositions in all strains were similar under a given condition indicating that staphyloxanthin does not influence fatty acid composition. Strain Pig1 had decreased membrane fluidity as measured by fluorescence anisotropy than the other strains under all conditions indicating that staphyloxanthin helps maintain membrane rigidity. We could find no evidence for correlation of expression of crtM and fatty acid biosynthesis genes. Supplementation of medium with glucose increased SCFA production and decreased BCFA and staphyloxanthin production, whereas acetate-supplementation also decreased BCFAs but increased staphyloxanthin production. We believe that staphyloxanthin levels are influenced more through metabolic regulation than responding to fatty acids incorporated into the membrane.
REVIEW | doi:10.20944/preprints201810.0307.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: Keywords: amniotic membrane; epithelialization; inflammation; ocular surface disorders; anti-fibrotic action, amniotic membrane eye drop, amniotic membrane graft transplantation.
Online: 15 October 2018 (12:06:21 CEST)
Abstract: The aim of this study is to emphasize on the clinical uses of amniotic membrane (AM) in multiple ocular disorders. AM possesses many properties including promotion of epithelialization, anti-fibrotic, anti-apoptotic, anti-angiogenic properties. Epithelial wound healing on the eye surface is promoted due to several epidermal and keratocyte growth factors as well as by its anti-inflammatory and anti-scarring effects due to interleukin-10, interleukin-1 receptor antagonists and inhibition of transforming growth factor- beta (TGF-β) signal transduction by AM in the corneal and conjunctival fibroblasts respectively. It plays a crucial role by functioning as a substitute of basement membrane (BM) and as a temporary graft material. It is not only being used as an eye graft but also its extract can be used as an eye drop for corneal and external eye diseases. So its proper preparation, preservation and clinical application can bring a revolutionary change in the treatment of different ocular disorders.
ARTICLE | doi:10.20944/preprints201801.0211.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: membrane transport; osmosis; interaction
Online: 23 January 2018 (06:43:31 CET)
A membrane can be represented by an energy landscape that solutes or colloids must cross. A model accounting for the momentum and the mass balances on the membrane energy landscape establishes a new way of writing for the Darcy law. The counter pressure in the Darcy law is no longer written as the result of an osmotic pressure difference but rather as a function of colloid-membrane interactions. The ability of the model to describe the physics of the filtration is discussed in detail. This model is solved on a simplified energy landscape to derive analytical relationships that describe the selectivity and the counter pressure from ab-initio operating conditions. The model shows that the stiffness of the energy landscape has an impact on the process efficiency: a gradual increase in interactions (like with hourglass pore shape) can reduce the separation energetic cost. It allows the introduction of a new paradigm to increase membrane efficiency: the accumulation that is inherent to the separation must be distributed across the membrane. Asymmetric interactions thus lead to direction-dependent transfer properties and the membrane exhibits diode behavior. These new transfer opportunities are discussed.
ARTICLE | doi:10.20944/preprints201709.0010.v1
Online: 4 September 2017 (18:25:01 CEST)
Titanium membranes are used for guided bone regeneration in implant therapy. However, as a bioinert material, titanium does not have the ability to accelerate bone formation. Various titanium surface treatments to confer bioactivity have been demonstrated; however, there are concerns about the influence of chemical treatments on the corrosion of thin titanium membranes. This study investigated the influence of surface modifications on the structure of thin titanium membranes. Titanium membranes of 20 µm thickness were treated with acid or alkali solutions, and we evaluated their surface structure, wettability, corrosion depth, and mechanical strength compared to non-treated membranes. Alkali-treated thin titanium membranes displayed the formation of nanoscale pore structures on their surfaces, enhanced hydrophilicity, and less corrosion depth compared with acid-treated membranes. Furthermore, the tensile strength of alkali-treated membranes was comparable to non-treated membranes. These results suggest that alkali treatment is an appropriate surface modification method for thin titanium membranes.
REVIEW | doi:10.20944/preprints202207.0180.v1
Subject: Medicine & Pharmacology, Behavioral Neuroscience Keywords: plasma membrane; membrane domains; nanodomains; neurotransmitter receptors; cannabinoids; acetylcholine receptor; cannabinoid receptor.
Online: 12 July 2022 (09:17:01 CEST)
Fifty years on from the classical fluid-mosaic model of Singer and Nicolson, current views of the plasma membrane portray a much more complex view of this interface region. Compartmentalization, together with transbilayer and lateral asymmetries, provide the structural foundation for functional specializations at the cell surface, including the active role of the lipid microenvironment in the modulation of membrane-bound proteins. The chemical synapse, the site where neurotransmitter-coded signals are decoded by neurotransmitter receptors, adds another layer of complexity to the plasma membrane architectural intricacy, mainly due to the need to accommodate a sizeable number of molecules in a minute subcellular compartment with dimensions barely reaching the micrometer. In this review, we discuss how Nature has developed suitable adjustments to accommodate different types of membrane-bound receptors and scaffolding proteins via membrane microdomains, and how this “efford-sharing” mechanism has evolved to optimize crosstalk or separation or coupling where/when appropriate. To this end, we use a fast ligand-gated neurotransmitter receptor, the nicotinic acetylcholine receptor, and a second-messenger G-protein coupled receptor, the cannabinoid receptor, as paradigmatic example.
ARTICLE | doi:10.20944/preprints202204.0230.v1
Subject: Life Sciences, Biochemistry Keywords: membrane pump theory; membrane potential; ion channel; Na/K ATPase; thermodynamics; elecrtromagnetism
Online: 26 April 2022 (06:11:34 CEST)
The membrane potential or resting potential of the neuron has been the subject of many studies. Although this theory explains the generation and maintenance of the membrane potential by direct or even facilitated diffusion, there are too many contradictions to doubt that these forces are sufficient or even at work in a process whose initial conditions are of rare complexity. The aim of this article is to show that already in the past, a competing theory has been developed whose hypothesis seems more scientifically sound. To confirm this last theory, Hirohisa Tamagawa carried out an experiment of great simplicity which makes it possible to invalidate the current theory and to question the teaching and the knowledge in Biology and Biophysics.
ARTICLE | doi:10.20944/preprints202204.0182.v1
Subject: Life Sciences, Biochemistry Keywords: membrane pump theory; membrane potential; ion channel; NA/K ATPase; Biophysics; Biology
Online: 20 April 2022 (03:42:28 CEST)
The generation and maintenance of membrane potential is a fundamental part of Membrane Pump Theory. One of the key points of this hypothesis is based on a natural or facilitated molecular diffusion through several types of ion channels and pumps like the Na/K ATPase. Following the principles of chemistry, electrostatics and geometry, it becomes clear that ion channels cannot function in this way. The ions channels cannot by their location have both a filter function and be ion concentrators, and the Na/K pump by its position in the membrane and by the proposed assumptions is not able to perform its regulatory function. The current model must absolutely be revised according to the current state of our knowledge and allow an advance in the understanding of the phenomena opening new research perspectives.
ARTICLE | doi:10.20944/preprints201807.0460.v1
Subject: Engineering, Other Keywords: N-nitrosamines; formation potential; membrane treatment; reverse osmosis; membrane fouling; pilot-scale
Online: 24 July 2018 (15:46:34 CEST)
This study investigated the removal characteristics of N-nitrosamines and their precursors at three pilot-scale water reclamation plants. These plants applies different integrated membrane systems: (1) microfiltration (MF) / nanofiltration (NF) / RO; (2) sand filtration/three-step RO; and (3) ultrafiltration (UF) / NF and UF / RO. Variable removal of N-nitrosodimethylamine (NDMA) by the RO membrane processes could be attributable to membrane fouling and feed water temperature. The effect of membrane fouling on N-nitrosamines removal was extensively evaluated at one of the plants by conducting one month of operation and chemical cleaning of the RO membrane element. Membrane fouling enhanced N-nitrosamines removal by the pilot-scale RO membrane process. This finding contributes to better understanding of variable removal of NDMA by RO membrane processes. This study also investigated the removal characteristics of N-nitrosamines precursors. The NF and RO membrane processes greatly reduced NDMA formation potential (FP), but the UF process had little effect. The contributions of MF, NF, and RO membrane processes for reducing FPs of NDMA, N-nitrosopyrrolidine (NPYR) and N-nitrosodiethylamine (NDEA) were different, suggesting different size distributions of their precursors.
Subject: Life Sciences, Biophysics Keywords: cytosolic phospholipase A2; electron microscopy; C2 domain; Golgi; membrane bending; membrane curvature; oligomerization
Online: 12 March 2020 (04:10:52 CET)
Group IV phospholipase A2α (cPLA2α) regulates the production of prostaglandins and leukotrienes via the formation of arachidonic acid from membrane phospholipids. The targeting and membrane binding of cPLA2α to the Golgi involves the N-terminal C2 domain whereas the catalytic domain produces arachidonic acid. Although most studies of cPLA2α concern its catalytic activity, it is also linked to homeostatic processes involving the generation of vesicles that traffic material from the Golgi to the plasma membrane. Here we investigate how membrane curvature influences the homeostatic role of cPLA2α in vesicular trafficking. The cPLA2α C2 domain is known to induce changes in positive membrane curvature, a process which is dependent on cPLA2α membrane penetration. We show that cPLA2α undergoes C2 domain-dependent oligomerization on membranes in vitro and in A549 cells. We found that the association of the cPLA2α C2 domain with membranes is limited to membranes with positive curvature, and enhanced C2 domain oligomerization was observed on vesicles ~50 nm in diameter. We demonstrated that the cPLA2α C2 domain generates cholesterol enriched Golgi-derived vesicles independently of cPLA2α catalytic activity. Our results therefore provide novel insight into the molecular forces that mediate C2 domain-dependent membrane localization in vitro and in cells.
ARTICLE | doi:10.20944/preprints201911.0012.v4
Subject: Materials Science, Polymers & Plastics Keywords: interfacial polymerization; in-situ FT-IR spectroscopy; thin-film composite membrane; nanofiltration membrane
Online: 8 January 2020 (09:04:29 CET)
The interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC) has been extensively utilized to synthesize nanofiltration (NF) membranes. However, it is still a huge challenge to monitor the IP reaction, because of the fast reaction rate and the formed ultra-thin film. Herein, two effective strategies were applied to reduce the IP reaction rate: (1) the introduction of hydrophilic interlayers between the porous substrate and the formed polyamide layer, and (2) the addition of macromolecular additives in the aqueous solution of PIP. As a result, in situ Fourier transform infrared (FT-IR) spectroscopy was firstly used to monitor the IP reaction of PIP/TMC with hydrophilic interlayers or macromolecular additives in the aqueous solution of PIP. Moreover, the formed polyamide layer growth on the substrate was studied in a real-time manner. The in situ FTIR experimental results confirmed that the IP reaction rates were effectively suppressed and that the formed polyamide thickness was reduced from 138 ± 24 nm to 46 ± 2 nm according to TEM observation. Furthermore, an optimized NF membrane with excellent performance was consequently obtained, which included boosted water permeation of about 141–238 (L/m2·h·MPa) and superior salt rejection of Na2SO4 > 98.4%.
ARTICLE | doi:10.20944/preprints202002.0263.v1
Online: 18 February 2020 (10:43:15 CET)
On the system Au(III)-HCl-A324H+Cl-, liquid-liquid extraction experiments were used to define the extraction equilibrium and the corresponding extraction constant, and the facilitated transport of this precious metal, from HCl solutions, across a flat-sheet supported liquid membrane was investigated, using the ionic liquid as carrier, as a function of hydrodynamic conditions, concentration of gold(III) (0.01-0.1 g/L), and HCl (0.5-6 M) in the feed phase, and carrier concentration (0.023-0.92 M) in the membrane. An uphill transport equation was derived considering aqueous feed boundary layer diffusion and membrane diffusion as controlling steps. The aqueous diffusional resistance (Δf) and the membrane diffusional resistance (Δm) were estimated from the proposed equation, being their values 241 s/cm an 9730 s/cm, respectively. The performance of the present carrier was compared against results yielded by other ionic liquids, and also it was investigated the influence that other metals had on gold(III) transport both from binary or quaternary solutions. Gold was finally recovered from receiving solutions as zero valent gold nanoparticles.
ARTICLE | doi:10.20944/preprints202001.0348.v1
Online: 29 January 2020 (04:35:25 CET)
PEBAX-2533/metal salt/Al salt membranes were prepared for mixed olefin/paraffin separation. PEBAX-2533 with 80% ether group and 20% amide group was suggested as the polymer matrix for comparison of separation performance according to the functional group ratio in copolymer PEBAX. In addition, Al salts were used to stabilize metal ions for a long time as additives. High permeance was expected with the proportion of high ether groups since these functional groups provided relatively permeable regions. As a result, the PEBAX-2533 composite membrane showed a selectivity of 5 (propylene/propane) with 10 GPU. However, the permeance of membrane was not unexpectedly improved and the selectivity was reduced. The result was analyzed by SEM, FT-RAMAN and TGA, including FT-IR. The reduction in separation performance was determined by FT-IR. From these results, in order to stabilize the metal ions interacting with the polymer through Al(NO3)3, it was concluded that specific ratio of amide group was needed in PEBAX as polymer matrix.
ARTICLE | doi:10.20944/preprints201902.0082.v1
Subject: Life Sciences, Biochemistry Keywords: positional isomerism; PUFA biosynthesis; membrane remodelling; membrane lipidomics; lipidomic analysis; fluidity; functional two photon microscopy
Online: 8 February 2019 (09:43:06 CET)
Palmitic acid metabolism involves delta-9 and delta-6 desaturase enzymes forming palmitoleic acid (9cis-16:1; n-7 series) and sapienic acid (6cis-16:1; n-10 series), respectively. The corresponding biological consequences and lipidomic research on these positional MUFA isomers are under development. Furthermore, sapienic acid can bring to the de novo synthesis of the n-10 polyunsaturated fatty acid (PUFA) sebaleic acid (5cis,8cis-18:2), but such transformations in cancer cells are not known. The model of Caco-2 cell line was used to monitor sapienic acid supplementation (150 and 300 μM) and evidence the formation of n-10 fatty acids as well as their incorporation at levels of membrane phospholipids and triglycerides. Comparison with palmitoleic and palmitic acids evidenced that lipid remodeling was influenced by the type of fatty acid and positional isomer, with increase of 8cis-18:1, n-10 PUFA and decrease of saturated fats in case of sapienic acid. Cholesteryl esters were formed only in case of sapienic acid. EC50 of sapienic acid (232.3 μM at 96 hrs) was the highest found among the tested fatty acids, thus influencing cell viability that was only reduced at 25% at 300 μM, whereas palmitoleic acid induced cell death. Two-photon fluorescent microscopy with Laurdan as a fluorescent dye provided information on membrane fluidity, highlighting that sapienic acid increases the distribution of fluid regions, probably connected with the formation of 8cis-18:1 and the n-10 PUFA in cell lipidome. Our results bring evidence for MUFA positional isomers and de novo PUFA synthesis for developing lipidomic analysis and cancer research.
ARTICLE | doi:10.20944/preprints202208.0510.v1
Online: 30 August 2022 (06:00:56 CEST)
The occurrence of potential spikes in a cell is a sign of life, and it is called action potential. There is a common notion that neuron signal conduction is the conduction of action potential. Hence, action potential is a typical and essential life activity. However, such potential spikes occur even in simple nonliving systems. According to the experimental observations by Pollack, structured water molecules can generate a negative potential environment. From this observation, the potential spike generation process for both living and nonliving systems caused by ion and water molecule adsorption-desorption process could be explained in this paper. So, taking into consideration the electrically neutral water molecules,the action potential generation mechanism could be explained. It is a fully inanimate model. Hence, the action potential may not be a life activity. Here, the role of water molecules in life is investigated further. It was found that the phase transition of the membrane is involved in the neuron signal conduction, but the membrane phase transition could be due to the change of state of the water molecules, which forms a large-scale structure in the cavities created by a number of lipids.
CASE REPORT | doi:10.20944/preprints202207.0045.v1
Online: 4 July 2022 (09:32:17 CEST)
Management of diabetic foot ulcers (DFUs) presents challenges to even the most experienced wound care providers. Because of the chronic, non-healing nature of many DFUs, advances in the treatment and care of this disease process are particularly relevant. This case study aims to report the efficacy of the application of dehydrated amniotic membrane allograft (DAMA) to a diabetic foot ulcer. The patient in this study is a 44-year-old male who presented with an aggressive infection on his right foot, which resulted in an open wound of 18 months duration. This patient received weekly applications of dual-layer DAMA over seven weeks. Upon examination at the initial application, the wound was classified as a Wagner grade 3 with necrosis of the underlying muscle. Upon inspection at the final visit, the wound was closed entirely. The results that were shown include improvements in the size, depth, edges, necrotic tissue amount, and epithelization of the wound. This case study demonstrates that the ap-plication of DAMA has the potential to augment the body’s natural DFU healing response; however, future nonrandomized and randomized controlled trials are needed to establish its efficacy further.
ARTICLE | doi:10.20944/preprints202012.0815.v1
Subject: Chemistry, Analytical Chemistry Keywords: Membrane Chemical Regeneration; Phosphoric Acid; Clarification
Online: 31 December 2020 (13:45:51 CET)
Various techniques have been used to “clean-up” industrial phosphoric acid: precipitation, flotation, activated charcoal or clay treatment. To address membrane processes potential in phosphoric acid clarification process, this study explores the advantage of membrane techniques as new route for phosphoric acid clarification in an eco-efficient way through the use of “regenerated spent membrane”. Regeneration of the spent membranes was performed on of 0.15 m2 active area regeneration. These membrane samples were used to study the phosphoric acid clarification at a laboratory scale. They were immersed in an oxidizer for at most seven days. The samples were characterized systematically before immersion in an oxidant media. In this study, the potential to regenerate spent membranes and application of this media to clarify the 29% P2O5 phosphoric acid was demonstrated. This study shows, by tests that the reverse osmosis (RO) membranes achieve an abatement of 70% and 65% for solids and organic materials, respectively. These positive results will pave the way for implementing these membranes phosphoric acid treatment process. Moreover, besides being economically advantageous, the use of the spent membrane is likely an environmentally friendly route (no waste, no organic solvent and effluent to be regenerated later on).
REVIEW | doi:10.20944/preprints202012.0569.v1
Subject: Materials Science, Biomaterials Keywords: AMD; Biomaterials; electrospinning; membranes; Bruch's membrane
Online: 23 December 2020 (07:23:19 CET)
Abstract: Age-related macular degeneration (AMD) is the leading cause of central blindness in developed countries. It affects people mainly over the age of 50 years. It is a disease of the macula, an area of the retina responsible for sharp central vision. It particularly affects the Bruch’s membrane (BM); a layer in the retina that acts as the basement upon which retinal pigment epithelial cells (RPE) attach and survive. The pathology of AMD is not fully understood, but age is considered the main risk factor. There are two forms; nonexudative, leading to the end-stage of the disease, called nonexudative (or dry) AMD (90% of cases) where fatty deposits called drusen form under the RPE on top of the BM lifting off the RPE, and neovascular (or wet) AMD (10% of cases) where abnormal new blood vessels grow and push through the BM, bleeding in and disrupting the RPE. Neovascular AMD is well controlled with regular antiangiogenic drug injections of anti-vascular endothelial growth factor (anti-VEGF) into the eye, whereas there is no current treatment for nonexudative AMD. Many research groups across the world are working on a treatment for nonexudative AMD. This review discusses the research currently being conducted including cell therapies, development of cell transplantation membranes, targeting other disease structures in affected retina (i.e. drusen), and drug delivery to the retina using nanoparticles. Finally, we include our research contributing to the field; developing a bioactive membrane intended to function two-fold: target diseased structures and transplant healthy RPE to the desired area.
ARTICLE | doi:10.20944/preprints202009.0531.v1
Subject: Life Sciences, Cell & Developmental Biology Keywords: polystyrene; tissue culture; cell membrane stability
Online: 23 September 2020 (03:46:57 CEST)
Unanticipated errors in scientific research data can be attributed to the unwarranted assumption of uniformity in the polystyrene surface that is ubiquitously used in tissue culture flasks and dishes. We have shown that when adherent cells are subjected to fluid shear force, equivalent to rinsing the culture with a balanced salt solution, cells on some areas of the polystyrene surface will immediately rupture while still adherent on the surface. This heterogeneity on the polystyrene surface can cause unexpected variability in experimental results and in replicating experiments among labs. In this paper a novel quantitative method is described to measure the degree of heterogeneity on the polystyrene surface of tissue culture flasks. The results show significant variation among several brands of tissue culture flasks as well as large variability within the production lot of a manufacturer. The assay method involves loading the cells with a fluorescent marker that is released upon membrane rupture. Cell membrane rupture also causes the loss of marker proteins used in Westernblots. This novel assay method can be used to monitor the batch consistency and the manufacturing process of flasks and dishes. It may also be used to test new biomaterials.
HYPOTHESIS | doi:10.20944/preprints201904.0210.v2
Subject: Life Sciences, Biochemistry Keywords: regulation; membrane; glycerophospholipid; composition; chemical activity
Online: 31 October 2019 (04:39:47 CET)
Mammalian cells maintain the complex glycerophospholipid (GPL) class compositions of their various membranes within close limits because this is essential to their well-being or viability. Surprisingly, however it is still not understood how those compositions are maintained except that GPL synthesis and degradation closely coordinated. Here, we hypothesize that abrupt changes in the chemical activity of the individual GPL classes coordinate the synthesis and degradation, as well other homeostatic processes. A previously proposed model proposed that in cellular membranes only a limited number of “allowed” or optimal GPL glass compositions exist because they are energetically more favorable than the other compositions, i.e. they represent local free energy minima (Somerharju et al. 2009). This model, however, could not satisfactorily explain how the optimal compositions are sensed by the key homeostatic enzymes i.e., the rate-limiting synthetizing enzymes and the degrading enzymes (i.e., homeostatic phospholipases). We now propose that when the mole fraction of a GPL class exceeds an optimal one, its chemical activity abruptly increases, which (i) increases its propensity to efflux from the membrane thus making it susceptible for hydrolysis by homeostatic phospholipases, (ii) increases its potency to inhibit its own biosynthesis via a feedback mechanism, (iii) enhances its conversion to another GPL class via a novel process termed “head group remodeling” or (iv) enhances its translocation to other subcellular membranes. Accordingly, abrupt changes in the chemical activity of the individual GPL classes is proposed to regulate and coordinate those four processes maintaining GPL class homeostasis in mammalian cells.
COMMUNICATION | doi:10.20944/preprints201811.0539.v1
Subject: Materials Science, General Materials Science Keywords: nickel; HER; anion exchange membrane; electrolysis
Online: 22 November 2018 (05:30:57 CET)
Anion exchange membrane (AEM) electrolysis is hampered by two main issues: stability and performance. Focusing on the latter, this work demonstrates a highly active NiMo cathode for hydrogen evolution in AEM electrolysis. We demonstrate an electrolyzer performance of 1 A cm−2 at 1.9 V (total cell voltage) with a NiMo loading of 5 mg cm−2 and an iridium black anode in 1 M KOH at 50 °C, that may be compared to 1.8 V for a similar cell with Pt at the cathode. The catalysts developed here will be significant in supporting the pursuit of cheap and environmentally friendly hydrogen fuel.
ARTICLE | doi:10.20944/preprints201807.0371.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: molecular simulation; membrane separations; ion-transport
Online: 20 July 2018 (04:24:45 CEST)
In this report we have discussed the important role of molecular modeling, especially the use of the molecular dynamics method, in investigating transport processes in nanoporous materials such as membranes. With the availability of high performance computers, molecular modeling can now be used to study rather complex systems at a fraction of the cost or time requirements of experimental studies. Molecular modeling techniques have the advantage of being able to access spatial and temporal resolution which are difficult to reach in experimental studies. For example, sub-Angstrom level spatial resolution is very accessible as is sub-femtosecond temporal resolution. Due to these advantages, simulation can play two important roles: Firstly because of the increased spatial and temporal resolution, it can help understand phenomena not well understood. As an example, we discuss the study of reverse osmosis processes. Before simulations were used it was thought the separation of water from salt was purely a coulombic phenomenon. However, by applying molecular simulation techniques, it was clearly demonstrated that the solvation of ions made the separation in effect a steric separation and it was the flux which was strongly affected by the coulombic interactions between water and the membrane surface. Additionally, because of their relatively low cost and quick turnaround (by using multiple processor systems now increasingly available) simulations can be a useful screening tool to identify membranes for a potential application. To this end, we have described our studies in determining the most suitable zeolite membrane for redox flow battery applications. As computing facilities become more widely available and new computational methods are developed, we believe molecular modeling will become a key tool in the study of transport processes in nanoporous materials.
ARTICLE | doi:10.20944/preprints201807.0108.v1
Subject: Materials Science, Nanotechnology Keywords: Zein; nanocomposite membrane; adsorption; wastewater; RB19
Online: 6 July 2018 (08:01:59 CEST)
The present work demonstrates the new nanofiber mats prepared through co-electrospinning of two different polymers i.e. corn protein namely Zein and Nylon-6. The composite nanofiber membrane was used as an effective adsorbent material for the removal of toxic reactive dye i.e. Reactive Blue 19 (RB 19) from water solution. These co-electrospun nanofibers had good mechanical strength compared to zein nanofibers alone. Experimental results suggested that zein/nylon nanofibers have greater potential for total removal of RB19 at room temperature within 10 min of contact time from aqueous solution. The maximum capacity was found to be 70 mg/g of nanofibers. The mechanism of RB19 removal on proposed nanofibers is mainly through hydrogen bond and electrostatic means.
ARTICLE | doi:10.20944/preprints202111.0067.v2
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: Ih current, lamotrigine, HCN channels, theta rhythm, local field potentials, IPSCs, membrane excitability, action potential, membrane resonance.)
Online: 5 November 2021 (11:31:29 CET)
Theta oscillations generated in hippocampal (HPC) and cortical neuronal networks are involved in various aspects of brain function, including sensorimotor integration, movement planning, memory formation and attention. Disruptions of theta rhythms are present in individuals with various disorders, including epilepsy and Alzheimer’s disease. Theta rhythm generation involves a specific interplay between cellular (ionic) and network (synaptic) mechanisms. HCN channels are theta modulators, and several medications are known to enhance their activity. We investigated how different doses of lamotrigine (LTG), an HCN channel activator, and antiepileptic and neuroprotective agent, would affect hippocampal theta rhythms in acute HPC slices (in vitro) and anaesthetized rats (in vivo). Whole-cell patch clamp recordings revealed that LTG decreased GABAA-fast transmission in CA3 and CA1 cells, in vitro. In addition, LTG directly depressed CA3 and CA1 pyramidal neuron excitability. These effects were partially blocked by ZD 7288, a selective HCN blocker, and are consistent with decreased excitability associated with antiepileptic actions. Lamotrigine also depressed hippocampal theta oscillations in vitro, also consistent with its neuronal depressant effects. In contrast, it exerted an opposite, enhancing effect, on theta recorded in vivo. The contradictory in vivo and in vitro results indicate that LTG increases ascending theta activating medial septum/entorhinal synaptic inputs that over-power the depressant effects seen in hippocampal neurons. These results provide new insights into LTG actions and indicate an opportunity to develop more precise therapeutics for the treatment of dementias, memory disorders and epilepsy.
REVIEW | doi:10.20944/preprints202110.0447.v1
Subject: Life Sciences, Biochemistry Keywords: UPR; IRE1; PERK; ATF6; lipid bilayer stress; ER stress; secretory pathway; hydrophobic mismatch; membrane thickness; membrane stiffness
Online: 29 October 2021 (07:57:29 CEST)
The endoplasmic reticulum (ER) is the major site of membrane biogenesis in most eukaryotic cells. As the entry point to the secretory pathway, it handles more than 10.000 different secretory and membrane proteins. The membrane insertion of proteins, their folding, and ER exit are affected by the lipid composition of the ER membrane and its collective membrane stiffness. The ER is also a hotspot of lipid metabolism for membrane lipids including sterols, glycerophospholipids, ceramides and neural storage lipids. The unfolded protein response (UPR) bears an evolutionary conserved, dual sensitivity to both protein folding-imbalances in the ER lumen and aberrant compositions of the ER membrane, referred to as lipid bilayer stress (LBS). Through transcriptional and non-transcriptional mechanisms, the UPR upregulates the protein folding capacity of the ER and balances the production of proteins and lipids to maintain a functional secretory pathway. In this review, we discuss how UPR transducers sense unfolded proteins and LBS with a particular focus on their role as guardians of the secretory pathway.
REVIEW | doi:10.20944/preprints202103.0473.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Pterygium; Platelet-rich membrane; Surgery; Ocular; Repair
Online: 18 March 2021 (10:59:34 CET)
Pterygium is a common ocular disease caused by abnormal cellular proliferation leading to abnormal fibrovascular growth of the conjunctiva. The main treatment is surgical removal; however, despite the improvement of surgical techniques and development of adjuvant therapies, postoperative recurrence, which can be as high as 89%, remains a challenge. Currently, pterygium excision with conjunctival autograft remains the preferred surgical technique to decrease recurrence, especially when combined with ciclosporin eye drops. Nevertheless, there is no gold standard surgical technique to prevent pterygium recurrence. Therefore, this review aims to assess the safety, effectiveness and, applicability of platelet-rich fibrin membrane for primary pterygium surgery and assess its possible benefits in resource-limited settings.
CASE REPORT | doi:10.20944/preprints202010.0244.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: HOCM; SAS; Subaortic Membrane; LVOTO; ASH; SAM
Online: 12 October 2020 (13:27:11 CEST)
Hypertrophic obstructive cardiomyopathy (HOCM) is an autosomal dominant disorder leading to left ventricular outflow tract obstruction (LVOTO). It can present with chest pain, syncope, breathlessness, or in some cases sudden cardiac death. Primarily, it is diagnosed based on echocardiographic findings but cardiac computed tomography (CT) or cardiac magnetic resonance imaging (MRI) can be helpful in selected cases. In this case report, we discuss a case of a young-aged female patient previously diagnosed as HOCM and presented with chest pain, shortness of breath, and palpitations. Her echocardiography revealed severe asymmetrically hypertrophied left ventricle (LV) with normal function and systolic anterior motion of the mitral valve was present and a subvalvular aortic membrane was also seen. The computed tomography (CT) was also performed showing severe asymmetrical hypertrophied and thickened trileaflet tricommissural aortic valve with no calcification or significant valvular aortic stenosis but there was a subaortic membrane (concentric only sparing anteriorly). The presence of subaortic membrane with HOCM is a rare finding and it can be a diagnostic challenge and untreated cases are susceptible to progressive heart failure and worsening of the symptoms by further increasing left ventricular outflow tract obstruction (LVOTO). A thorough investigation and planning before surgical intervention is required to achieve optimal results.
ARTICLE | doi:10.20944/preprints201904.0087.v1
Subject: Materials Science, Polymers & Plastics Keywords: thermoplastic polyurethane; foaming; perforated structure; membrane; filtration
Online: 8 April 2019 (11:24:16 CEST)
The way in which a perforated structure is formed has attracted much interest in the porous membrane research community. This novel structure gives materials an excellent antifouling property as well as a low operating pressure and other benefits. Unfortunately, the current membrane fabrication methods usually involve multi-step processes and the use of organic solvents or additives. Our study is the first to offer a way to prepare perforated membrane by using a physical foaming technique with CO2 as the blowing agent. We selected thermoplastic polyurethane (TPU) as the base material because it is a biocompatible elastomer with excellent tensility, high abrasion resistance, and good elastic resilience. Various processing parameters, which included the saturation pressure, the foaming temperature, and the membrane thickness, were applied to adjust the TPU membrane’s perforated morphology. We proposed a possible formation mechanism of the perforated membrane. The as-prepared TPU membrane had good mechanical properties with a tensile strength of about 5 MPa and an elongation at break above 100%. Such mechanical properties make this novel membrane usable as a self-standing filter device. In addition, its straight-through channel structure can separate particles and meet different separation requirements.
ARTICLE | doi:10.20944/preprints201811.0359.v1
Subject: Materials Science, Nanotechnology Keywords: Carbon; nanofiber; membrane; urease; biomolecules; water treatment
Online: 15 November 2018 (11:08:43 CET)
Development of carbon nanomaterials for adsorption thus removal of organic pollutants from water is a progressive research subject. In this regard, carbon nanomaterials with bifunctionality towards polar and non-polar or even amphiphilic undesired materials is indeed attractive for further study and implementation. Here, we created carbon buckypaper adsorbents comprising amphiphilic (oxygenated amorphous carbon (a-COx)/graphite (G)) nanofilaments that can dynamically adsorb organic biomolecules (i.e. urease enzyme) and thus purify the wastewaters of relevant industries. Given the dynamic conditions of the test, the adsorbent was highly efficient in adsorption of the enzyme (88%) while permeable to water (2382 L.h-1.m-2), thus holds a great promise for further development and upscaling. A subsequent citric acid functionalization declined selectivity of the membrane to urease, implying the biomolecules adsorb mostly via graphitic domains rather than oxidized, polar amorphous carbon ones. The devised platform i.e. the urease functionalized buckypaper is optimally conductive (13 S.cm-1) and can be further employed as a biosensor. Accordingly, water treatment can be linked to biosensing via a nanostructured membrane.
REVIEW | doi:10.20944/preprints201709.0162.v1
Online: 29 September 2017 (18:32:40 CEST)
The efficacy of chemotherapy depends on sensitivity and intrinsic or acquired drug resistance of cancer cells. The n-3 long chain polyunsaturated fatty acids (n-3 LCPUFAs) are considered chemosensitizing agents and revertants of multidrug resistance by pleiotropic mechanisms. The specific mechanisms are not fully understood, but nowadays, it is widely accepted that there are a complex network of mechanisms, including alteration in gene expression, modulation of cellular proliferation and differentiation, induction of apoptosis, generation of reactive oxygen species and lipid peroxidation. A crucial mechanism in the control of cell drug uptake and efflux is related to n-3 LCPUFA influence on membrane lipid composition. The incorporation of docosahexaenoic acid in the lipid rafts produces significant changes in their physical-chemical properties affecting content and functions of transmembrane proteins, such as growth factors, receptors and ATP-binding cassette transporters. Of note, n-3 LCPUFAs often impact on the lipid compositions more in chemoresistant cells than in chemosensitive cells, suggesting their adjuvant role in cancer treatment.
ARTICLE | doi:10.20944/preprints201807.0612.v1
Subject: Engineering, Civil Engineering Keywords: translucent textile membrane roof, climate-based daylight modelling, daylight performance, energy conservation, translucent thermal insulation, multi-layer membrane
Online: 31 July 2018 (08:58:49 CEST)
Daylight usage in buildings improves visual comfort and lowers the final energy demand for artificial lighting. The question always occurs: how much conservation can you achieve? New upcoming or rare materials and constructions have a lack of information about their application. Therefore, the current work investigates the daylight performance of a multi-layer textile membrane roof with 2 300 m² on top of a sports hall. A translucent, thermal insulation with a glass fibre fleece between the roof membranes combines daylight usage and heating demand reduction. A sports hall with built year 2017 is selected as the case study building. The optical properties of the roof construction are measured. The (visual) light transmittance amounts to 0.72 % with a clean surface. An accordingly parametrized climate-based annual daylight modeling delivers daylight indicators for different construction scenarios. The results show that in comparison to only one glass facade, the additional translucent and thermally insulated membrane construction increases the annual daylight autonomy700/ continuous DA700 from 0/ 15 % to 1.5/ 38 %. In the roof covered areas of the sport field, this results in a reduction from 19.7 to 13.8 kWhel/m²/a electricity for the artificial lighting with dim control (30 % savings). Also, the influence of soiling on the light transmittance was determined with a relevant reduction of one layer about a factor 0.81. The novel results are of great value as a comparison and benchmark for planners and future buildings of similar type.
REVIEW | doi:10.20944/preprints202207.0108.v1
Subject: Life Sciences, Biochemistry Keywords: membrane curvature; molecular dynamics; simulations; BAR domain; trafficking
Online: 7 July 2022 (04:19:42 CEST)
Eukaryotic cells contain membranes with various curvatures, from the near-plane plasma membrane to the highly curved membranes of organelles, vesicles, and membrane protrusions. These curvatures are generated and sustained by curvature-inducing proteins, peptides, and lipids, and describing these mechanisms is an important scientific challenge. In addition to that, some molecules can sense membrane curvature and a thereby be trafficked to specific locations. The description of curvature-sensing is another fundamental challenge. Curved lipid membranes and their interplay with membrane-associated proteins can be investigated with molecular dynamics (MD) simulations, given the right tools. Various methods for simulating curved membranes with MD are discussed here, including tools for setting up simulation of vesicles, and methods for sustaining membrane curvature. The latter are divided into methods that exploit scaffolding virtual beads, methods that use curvature-inducing molecules, and methods applying virtual forces. The variety of simulation tools allow the researcher to closely match the conditions of experimental studies of membrane curvatures.
ARTICLE | doi:10.20944/preprints202102.0204.v1
Subject: Life Sciences, Biochemistry Keywords: Lipidome; High Five insect cells; Membrane proteins; Biomembranes
Online: 8 February 2021 (12:23:09 CET)
The lipid composition of biomembranes influence the properties of the lipid bilayer as well as that of the proteins. In this study, the lipidome and the lipid/protein ratio of membranes from High FiveTM insect cells overexpressing mouse P-glycoprotein was characterized. This provides a better understanding of the lipid environment in which P-glycoprotein is embedded, and thus of its functional and structural properties. The relative abundance of the distinct phospholipid classes and their acyl chain composition was characterized. A mass ratio of 0.57 +/- 0.11 phospholipids to protein was obtained. Phosphatidylethanolamines are the most abundant phospholipids, followed by phosphatidylcholines. Membranes are also enriched in negatively charged lipids (phosphatidylserines, phosphatidylinositols and phosphatidylglycerols), and contain small amounts of sphingomyelins, ceramides and monoglycosilatedceramides. The most abundant acyl chains are monounsaturated, with significant amounts of saturated chains. The characterization of the phospholipids by HPLC-MS allowed identification of the combination of acyl chains, with palmitoyl-oleoyl being the most representative for all major phospholipid classes except for phosphatidylserines, which are mostly saturated. A mixture of POPE:POPC:POPS in the ratio 45:35:20 is proposed for the preparation of simple representative model membranes. The adequacy of the model membranes was further evaluated by characterizing their surface potential and fluidity.
HYPOTHESIS | doi:10.20944/preprints202012.0657.v1
Subject: Biology, Anatomy & Morphology Keywords: monophyly; progenotes; membrane evolution; origin of biological systems
Online: 25 December 2020 (12:29:28 CET)
Cells occupy a prominent place in the history of life on planet Earth. The central role of cellular organization is observed by the fact that “cellular life” is often used as a synonym for life itself. Thus, most characteristics used to define cells overlap with the ones used to define life. Notwithstanding, new scenarios about the origin of life are bringing alternative views to describe how cells may have evolved from the open biological systems named progenotes. Here, using a logical and conceptual analysis, we re-evaluate the characteristics used to infer a single origin for cells. We argue that some evidences used to support cell monophyly, such as the presence of elements from both the translation mechanism and the universality of the genetic code, actually indicate a unique origin for all “biological systems”, a term used to define not only cells, but also virus and progenotes. Besides, we present evidence that at least two biochemical pathways as important as (i) DNA replication and (ii) lipid biosynthesis may not homologous between Bacteria and Archaea. The identities observed between the proteins involved in those pathways along representatives of these two ancestral Domains are too low to indicate common genic ancestry. Altogether these facts can be seen as an indication that cellular organization has possibly evolved two or more times and that LUCA (the Last Universal Common Ancestor) might not have existed as a cellular entity. Thus, we aim to consider the possibility that different strategies acquired by biological systems to exist, such as viral, bacterial and archaeal were originated independently from the evolution of different progenote populations.
REVIEW | doi:10.20944/preprints202009.0513.v1
Subject: Life Sciences, Molecular Biology Keywords: PIP2; membrane dynamics; disease; actin dynamics; phosphoinositides; signaling
Online: 22 September 2020 (09:04:28 CEST)
In this review we summarize the recent development in understanding the role of PIP2 in cellular function and signaling. We first discuss the effect of PIP2 on actin binding proteins addressing the mechanism of the actin cytoskeletal dynamics such as polymerization or depolymerization of the filamentous network or the coupling to membrane to generate forces. Next, we outline the role of PIP2 in membrane dynamics. We summarized how the membrane organization depends upon PIP2 in the presence of ions or transmembrane proteins that are sensitive to membrane curvature. We discuss how clathrin coated pits interact with adaptor proteins during the endocytosis process, which is facilitated by PIP2. Finally, we discuss the role of PIP2 in cell signaling and diseases.
ARTICLE | doi:10.20944/preprints202008.0529.v2
Subject: Life Sciences, Biophysics Keywords: membrane potential; Nernst; Bernstein; action potential; propagation; theory
Online: 9 September 2020 (09:24:15 CEST)
Man has always been interested in animal electricity, which seems to be measured in every living cell. He has been fascinated by trying to elucidate the mechanisms by which this potential is created and maintained. Biology is the science that seeks to explain this mystery. Biology is based on basic sciences such as physics or chemistry. The latter, in turn, make systematic use of mathematics to measure, evaluate and predict certain phenomena and to develop "laws" and models that are as general as possible while respecting, as closely as possible, observations and facts. The Nernst equation was one of the pillars of electrochemistry. Biology also uses this same equation as one of the indispensable bases for the computation of membrane potential. Man has established a cellular model that highlights this equation in several forms. However, we are going to show by various means that this model is inadequate or even inapplicable.
ARTICLE | doi:10.20944/preprints202007.0655.v1
Subject: Materials Science, Biomaterials Keywords: dialysis membrane; ectosomes; exosomes; FTIR; infrared spectroscopy; purification
Online: 27 July 2020 (00:46:38 CEST)
Recent years brought great focus in the field of development of extracellular vesicles (EVs) based drug-delivery systems. Considering possible applications of EVs as a drug carriers the isolation process is a crucial step. To solve problems related with EV isolation, we created and validated a new EVs isolation method – Low Vacuum Filtration (LVF) and compared it with two commonly applied procedures - differential centrifugation (DC) and ultracentrifugation (UC). EVs isolated from endothelial cells culture media have been characterized by a) transmission electron microscopy (TEM) b) nanoparticle tracking analysis (NTA), c) western blot and d) Fourier-Transform Infrared Spectroscopy (FTIR). Additionally, the membrane surface have been imaged with Environmental Scanning Electron Microscopy (ESEM). We showed that LVF is reproducible and efficient method for EVs isolation form conditioned media. Additionally, we observed correlation between ATR-FTIR spectra quality and the EVs and proteins concentration. ESEM imaging confirmed that actual pore diameter are close to the values calculated theoretically. LVF method is an easy, fast and inexpensive EVs isolation method which allows for isolation of both ectosomes and exosomes from high volume sources with good repeatability. We think that it could be an efficient alternative for commonly applied methods.
ARTICLE | doi:10.20944/preprints202007.0059.v1
Subject: Life Sciences, Biophysics Keywords: plasma membrane; rafts; microemulsion; phase-separation; domain size
Online: 5 July 2020 (10:09:41 CEST)
It is widely, but not universally, believed that the lipids of the plasma membrane are not uniformly distributed, but that "rafts'' of sphingolipids and cholesterol float in a "sea'' of unsaturated lipids. The physical origin of such heterogeneities is often attributed to a phase coexistence between the two different domains. We argue that this explanation is untenable for several reasons. Further we note that the results of recent experiments are inconsistent with this picture. However they are quite consistent with an alternate explanation, namely that the plasma membrane is an emulsion of the two kinds of regions. To show this, we briefly review a simplified version of this theory and its phase diagram. We also explicate the dependence of the predicted domain size on four physical parameters. Among them are the spontaneous curvature of the membrane and its bending modulus and surface tension. Taking values of the latter two from experiment, we obtain domain sizes for several different cell types that vary from 58 to 88 nm.
ARTICLE | doi:10.20944/preprints202002.0008.v1
Subject: Engineering, General Engineering Keywords: ceramic membrane; combination process; microfiltration; optimization; recovery efficiency
Online: 3 February 2020 (03:58:04 CET)
The aim of this study is to evaluate the optimal conditions of membrane filtration process. Both laboratory test and pilot-scale test were conducted to examine a treated water on blending water. The water sample were prepared by blending a raw water and the effluent water filtered through an organic membrane. The optimal efficiency in the treatment of water quality at the lab-scale test was generated under conditions of flux at 2.0 m3/m2∙day, the blending ratio of 4:1, and the optimal dosage of coagulant at 20 ppm. The pilot-scale test resulted in that the optimal efficiency was obtained under conditions of flux at 2.0 m3/m2∙day and the blending ratio of 6.0:1. However, the different results between lab-scale and pilot-scale tests on the optimal dosage of coagulant implied that it is difficult to achieve the stable condition of process operation at the low level of coagulant. In summary, the results indicated that, in the combination process of organic membrane and ceramic membrane, the recovery efficiency was achieved above the level of 98.4 %. Compared to 92.1 % in a single organic membrane process, the combination process is 6.3 % more efficient than the single one. This combination process of water treatment lead to stable recovery rates by the optimal input of dosage, less pollution load to water, and a stabilized filtration system.
ARTICLE | doi:10.20944/preprints201906.0061.v1
Subject: Chemistry, Analytical Chemistry Keywords: new, sulbatamol sulphate, membrane electrode , utilizing for determination
Online: 7 June 2019 (13:49:13 CEST)
A new sulbatamol sulphate SBS membrane electrode was prepared that utilizing for its determination ; depend on the forming of the association complex ion of sulbatamol sulphate by the phosphotungstate counter anion deposed in poly vinyl chloride PVC polymer, by use a (Di-n- Octyl Phenyl Phthalate)(Dopp) as the plastizier substance, in membrane.The features properties as well as the behavior of it .The new electrode have been elaborated. The concentrations of medicine by utillizing This sensor show a fast, stable, near-Nernstian response in the range (1x10-1-1x10-6) mol/ L were determined with correlation coefficient of about (r = 0.9991) and with of a relative standard about 0.416 additionally deviation relative standard error of 1.710 %.pot The nernast linearity slop was founded and it is equal to 28.9 mV/decade and the detection limit was 4.1 x 10-6 mol/ L.The electrode selectivity coefficient Ki,j was calculated, in the existence of several interferences cations with confirmed medicine solutions. It was found the pH range response is in the range of (3 -7), with the response time of (30 – 116) sec. for various concentrations at room temperture , the lifetime for electrode was found to be more than 21 days. The electrode was successfully used for potentiometric limitation of sulbatamol sulphate in several pharmaceutical drugs by using direct potentiometry.
ARTICLE | doi:10.20944/preprints201903.0068.v2
Subject: Chemistry, Chemical Engineering Keywords: germanium; supported liquid membrane; transport; Cyanex 923; modeling
Online: 29 May 2019 (04:54:50 CEST)
A transport process was studied from an aqueous solution containing oxalic acid and 100 mg/L Ge using a flat sheet supported liquid membrane (FSSLM) system. Cyanex 923 immobilized in a polytetrafluoroethylene membrane was employed as a carrier. The solution chemistry and related diagrams were applied to study the transport of germanium. The effectual parameters such as oxalic acid, carrier concentration, and strip reagent composition were evaluated in this study. Based on the results, the oxalic acid concentration of 0.075 mol/L and the carrier concentration of 20 %v/v were the condition in which the efficient germanium transport occurred. Among strip reagents, NaOH (0.04-0.1 mol/L) had the best efficiency to transport germanium through the SLM system. Furthermore, the permeation model was obtained to calculate the mass transfer resistances of the membrane (Δm) and feed (Δf) phases. According to the results, the values of 1 and 1345 s/cm were evaluated for Δm and Δf, respectively.
ARTICLE | doi:10.20944/preprints201903.0227.v2
Subject: Biology, Horticulture Keywords: oxidative stress; enzymatic antioxidants; malondialdehyde; membrane permeability; chlorophyll
Online: 28 March 2019 (11:15:50 CET)
Scarcity of water is one of the most serious concerns in plant biology with diverse implications at all the levels of molecular, biochemical, and physiological phenomena of plant growth, development, and consequently the productivity. Most of the strategies to induce or enhance drought tolerance in plants are unreasonably expensive and/or time-consuming. Some studies conducted in the recent past have shown that plant growth regulators (PGRs) may induce/improve physiological tolerance in plants to cope with adverse environmental conditions including drought. The present study was aimed at investigating the effects of foliar spray of GABA (0, 1, 2, and 4 mM) applied 20 days following the germination of seeds, on vegetative growth, morphological characteristics, integrity of cell-membrane, and the levels of photosynthetic pigments and enzymatic antioxidants in carrot cvs. Supertaj and Bharat, grown under 100% and 50% field capacity of soil moisture. The treated and untreated (control) carrot plants were harvested and analyzed 2 weeks following the GABA application. The results revealed that foliar application of GABA improved the vegetative growth and significantly increased the levels of free amino acids, plastid pigments, enzymatic antioxidants, and the relative water content in the root crop grown under 50% field capacity of soil moisture, compared to control. Additionally, the GABA application decreased the electrolyte leakage of ions and melondialdehyde (MDA) content in carrot leaves. The carrots harvested from GABA-treated or untreated (control) plants were not significantly different for their protein contents. In conclusion, the incorporation of GABA in the production management of carrots may help plants to mitigate the adverse effects of water deficit stress.
ARTICLE | doi:10.20944/preprints201810.0551.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: RMM; membrane modules; modelling; material exchanger; permeation experiments
Online: 24 October 2018 (05:57:34 CEST)
Hydrogen is a promising energy carrier, exploitable to extract energy from fossil fuels, biomasses as well as intermittent renewable energy sources and its generation from fossil fuels with CO2 separation at the source is one of the most promising pathway for fossil fuels utilization. This work is focused on a particular configuration, called Reformer and Membrane Module (RMM), which alternates stages of Steam Reforming (SR) reaction with H2 separation stages to overcome the thermodynamic limits of the conventional SR. The configuration has numerous advantages with respect to the more studied and tested membrane reactors and has been tested on a pilot scale during a pilot-scale research project. Although the numerous modelling works appeared in the literature, the design features of the material exchanger (in the so-called RMM architecture) of different geometrical configurations have not been developed and the mass transfer correlations, capable of providing design tools useful for such membrane modules, are not available. The purpose of this work is therefore to apply a physical-mathematical model of the mass transfer, in three different geometries, considering both concentration polarization and membrane permeation, in order to: i) simulate the cited experimental results, ii) estimate the scaling-up correlations for the “material exchange modules”; iii) identify the mass transfer limiting regime in relation to the gas mass flow rate.
ARTICLE | doi:10.20944/preprints201810.0520.v1
Subject: Chemistry, Analytical Chemistry Keywords: MIMS; monochloramine; FTICR; chemical ionization; in-membrane reaction
Online: 23 October 2018 (05:44:42 CEST)
Membrane Inlet Mass Spectrometry (MIMS) was used to analyze monochloramine solutions (NH2Cl) and ammonia solutions in a compact FTICR. Chemical ionization enables identification and quantification of the products present in the permeate. The responses of protonated monochloramine and ammonium increase linearly with the solution concentration. The enrichments were respectively 1.2 and 5.5. Pervaporation is dependent on pH and only the basic form of ammonia NH3 pervaporates through the membrane. Unexpectedly, the small ammonia molecule permeated very slowly. It could be due to interactions with water molecules inside the membrane that create clusters. Moreover, NH2Cl solutions, in addition to the NH3Cl+ signal, presented a strong NH4+ signal at m/z 18.034 . Ammonia presence in the low-pressure zone before ionization is probable as NH4+ was detected with all the precursors used, particularly CF3+ and trimethylbenzene that presents a proton affinity higher than monochloramine. Ammonia may be formed inside the membrane due to the fact that NH2Cl is unstable and may react with the water present in the membrane. Those results highlight the need for caution when dealing with chloramines in MIMS and more generally with unstable molecules.
ARTICLE | doi:10.20944/preprints201711.0080.v1
Subject: Materials Science, Surfaces, Coatings & Films Keywords: PVDF membrane; coagulation bath temperature; polymer molecular weight
Online: 14 November 2017 (10:48:54 CET)
The global polyvinyldene flouride market is estimated to reach $937,278.5 thousand by 2019, therefore to develop new membranes and gain pioneering ideas, which could create innovative business opportunities, a fundamental knowledge about membrane properties fabricated from recent commercially available PVDF polymers is highly mandatory. In this study, we successfully prepared nine non-woven supported PVDF membranes using a phase inversion precipitation method starting from a 15 wt% PVDF solution in N-methyl-2-pyrrolidone. Various membrane morphologies were obtained by using (1) PVDF polymers with diverse molecular weight in a range from 300.000 Da to 700.000 Da and (2) different temperatures of the coagulation bath (20, 40, and 60 ±2°C) used for the films precipitation. Environmental Scanning Electron Microscope (ESEM) was used for surface and cross-section morphologies characterization. Atomic Force Microscope (AFM) was employed to investigate surface roughness, while Contact Angle (CA) instrument was used for membranes wettability studies. Fourier Transform Infrared Spectroscopy (FTIR) results show that the fabricated membranes are formed by a mixture of TGTG’ chains in α phase crystalline domains and all-TTTT trans planar zigzag chains characteristic to β phase. Moreover, generated results indicate that the phases content and membrane morphologies depend on the polymer molecular weight and conditions used for the membranes preparation. The diversity of fabricated membranes could be applied by the End User Industries for different applications.
REVIEW | doi:10.20944/preprints201706.0046.v1
Subject: Engineering, General Engineering Keywords: Reverse osmosis; Membrane fouling; Fouling indices; Predicting models
Online: 9 June 2017 (11:04:40 CEST)
ARTICLE | doi:10.20944/preprints202110.0313.v1
Subject: Chemistry, Applied Chemistry Keywords: membrane transport; Cyanex 923; iron(III); manganese (II); separation.
Online: 21 October 2021 (14:10:48 CEST)
The transport of iron(III) from Fe(III)-Mn(II)-HCl mixed solutions through a flat-sheet supported liquid membrane is investigated, being the carrier phase of Cyanex 923 (commercially available phosphine oxide extractant) dissolved in Solvesso 100 (commercially available diluent), as a function of hydrodynamic conditions, concentration of manganese and HCl in the feed phase, and carrier concentration in the membrane phase. A transport model is derived that describes the transport mechanism, consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion of the Fe(III)-Cyanex 923 complex across the membrane phase. The membrane diffusional resistance (Δm) and feed diffusional resistance (Δf) are calculated from the model, and their values are 145 s/cm and 361 s/cm, respectively. It is apparent that the transport of iron(III) is mainly controlled by diffusion through the aqueous feed boundary layer, being the thickness of this layer calculated as 2.9x10-3 cm. Since Mn(II) is not transported through the membrane phase, the present system allows to the purification of this manganese-bearing solutions.
ARTICLE | doi:10.20944/preprints202109.0436.v1
Online: 24 September 2021 (13:00:37 CEST)
Cesarean Section (CS) is one of the most frequently executed surgical procedures in gynecology and obstetrics. After a cesarean section, surgical site infection (SSI) increases hospital stay, lengthens maternal morbidity, and upsurges treatment costs. The current study determines the prevalence and risk factors for surgical site infection following cesarean section in China. A retrospective study was conducted on 23 cases of pregnant women who underwent cesarean section and incision severe infection and detection from March 2017 to January 2020 at Wuhan Maternal and Child Healthcare Hospital in China as the study group, and 20 cases of uninfected cesarean section during the same period were selected as the control group. Data were compared with the controls based on study variables and the presence of SSI. The mean age was 31±2.6. High fever and blood loss were observed in serous SSI-infected patients. The incidence rate of severe surgical site infection was 0.15 %. SSI was observed to be expected in pregnant women who had premature rupture of membrane before surgery (p < 0.001), who underwent postoperative antibiotic therapy (p < 0.001), and the patients who had gestational diabetes mellitus (p <0.001) and hematoma (p < 0.001) during surgery. Hence, following a cesarean section, surgical site infection is common. This research discovered several modifiable risk factors. SSI is associated with multifactorial rather than a single one. The development and strict implementation of a procedure by all health care practitioners can successfully reduce and prevent infection rates following cesarean section.
ARTICLE | doi:10.20944/preprints202108.0478.v1
Subject: Biology, Plant Sciences Keywords: antioxidant activity; chlorophyll; glycinebetaine; membrane stability index; salt stress
Online: 25 August 2021 (08:19:23 CEST)
Tagetes genus of Composite family consider one of the most favorite floriculture plant. Therefore, of particular interest examine the salt tolerance of this bedding and coloring agent plant. In this research, was report the role of glycinebetaine (GB) in attenuating the adverse impacts of salt stress in African marigold plant, along with their anti-oxidative capacities and biochemical attributes. The salt stressed African marigold (100 and 150 mM NaCl) was treated with GB at 200 mM, beside untreated control plants. According to the obtained results, the growth characters were negatively in salt stressed plants but a mitigate impact of GB were observed in this respect. Obviously, the morphological as well as some physiological characters were reduced with salinity treatments while GB treatment reverses these effects. Overall, the alleviate impact of GB on the negative impact of salt stress was enhanced through improving total phenolic and antioxidant enzyme activity. Further, it is concluded that GB concentration induces the activities of antioxidative enzymes which scavenged ROS increased under saline conditions.
ARTICLE | doi:10.20944/preprints202107.0204.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Intensive Care Units; Workforce; Mechanical Ventilation; Extracorporeal Membrane Oxygenation
Online: 8 July 2021 (13:34:14 CEST)
Aim: The aim of this study was to estimate the number of nurses who independently care for pa-tients with severe respiratory failure receiving mechanical ventilation (MV) or veno-venous ex-tracorporeal membrane oxygenation (VV-ECMO). Additionally, the study analyzed the actual role of nurses in the treatment of patients with MV and VV-ECMO. Methods: We conducted a cross-sectional study using postal surveys. The study included 725 Japanese intensive care units (ICUs). Descriptive statistics were conducted. Results: Among the 725 ICUs, we obtained 302 re-sponses (41.7%) and analyzed 282 responses. The median number of nurses per bed was 3.25. The median proportion of nurses who independently cared for patients with MV was 60% [IQR: 42.3-77.3]. The median proportion of nurses who independently cared for patients with VV-ECMO was 46.9 (35.7-63.3%) in the ICU experiencing VV-ECMO use. Concerning task-sharing, 33.8% of ICUs and nurses did not facilitate weaning from MV. Nurses always ti-trated sedatives in 44.5% of ICUs. Conclusion: Nurse staffing might be inadequate in all ICUs, es-pecially for severe respiratory failure. The proportion of competent nurses for caring for severe respiratory failure in ICUs should be considered when determining the work force of nurses.
ARTICLE | doi:10.20944/preprints202106.0428.v1
Subject: Physical Sciences, Acoustics Keywords: whispering gallery modes; microsphere; membrane; pressure sensor; optical interference
Online: 16 June 2021 (09:28:30 CEST)
We propose the physical proof-of-concept of a new simple miniature pressure sensor based on the whispering gallery modes (WGMs) optically excited in a dielectric microsphere placed near a flexible reflective membrane, which acts as an ambient pressure sensing element. WGMs excitation is carried out by free-space coupling of optical radiation to a microsphere. The distinctive feature of proposed sensor design is double excitation of optical eigenmodes by forward and backward propagating radiation reflected from a membrane that causes WGMs interference in particle volume. The optical intensity of resulting resonant field established in the microsphere carries information about the exact position of the pressure-loaded reflecting membrane. The sensitivity of the proposed sensor strongly depends on the quality factor of the excited resonant mode, as well as geometrical and mechanical parameters of the flexible membrane. We propose to register not the displacement of the position of the WGM resonance, but the change in its amplitude under the influence of the change in the distance between the sphere and the mirror under the influence of pressure. Important advantages of the proposed sensor are miniature design (linear sensor dimensions depends only on the membrane diameter) and the absence of a mechanical contact of pressure-sensitive element with WGM resonator.
ARTICLE | doi:10.20944/preprints202105.0678.v1
Subject: Engineering, Automotive Engineering Keywords: reactive electrochemical membrane; porous electrode; anodic oxidation; hydroxyl radicals.
Online: 27 May 2021 (14:11:27 CEST)
In recent years, electrochemical methods utilizing reactive electrochemical membranes (REM) have been recognized as the most promising technologies for the removal of organic pollutants from water. In this paper, we propose a 1D convection-diffusion-reaction model concerning the transport and oxidation of oxalic acid (OA) and oxygen evolution in the flow-through electrochemical oxidation system with REM. It allows the determination of unknown parameters of the system by treatment of experimental data and predicts the behavior of the electrolysis setup. There is a good agreement in calculated and experimental data at different transmembrane pressures and initial concentrations of OA. The model provides an understanding of the processes occurring in the system and gives the concentration, current density, potential and overpotential distributions in REM. The dispersion coefficient was determined as a fitting parameter and it is in good agreement with literary data for similar REMs. It is shown, that the oxygen evolution reaction plays an important role in the process even under the kinetic limit, and its contribution decreases with increasing total organic carbon flux through the REM.
REVIEW | doi:10.20944/preprints202010.0310.v1
Subject: Life Sciences, Biochemistry Keywords: Ras; nanocluster; Raf; dimerization; Ras orientation; membrane; HVR; structure
Online: 14 October 2020 (14:22:52 CEST)
Ras is the most frequently mutated oncogene and recent drug development efforts have spurred significant new research interest. Here we will review progress toward understanding how Ras functions in nanoscale, proteo-lipid signaling complexes on the plasma membrane, called nanocluster. We will discuss how G-domain reorientation is plausibly linked to Ras-nanoclustering and -dimerization. We will then look at how these mechanistic features could cooperate in the engagement and activation of RAF by Ras. Moreover, we will show how this structural information can be integrated with microscopy data that provide nanoscale resolution in cell biological experiments. Synthesizing the available data, we propose to distinguish between two types of Ras nanoclusters, an active, immobile RAF-dependent type and an inactive/ neutral membrane anchor-dependent. We conclude that it is possible that Ras reorientation enables dynamic Ras dimerization, while the whole Ras/ RAF complex transits into an active state. These transient di/oligomer interfaces of Ras may be amenable to pharmacological intervention. We close by highlighting a number of open questions including, whether all effectors form active nanoclusters and whether there is an isoform specific composition of Ras nanocluster.
ARTICLE | doi:10.20944/preprints202005.0439.v3
Subject: Life Sciences, Biochemistry Keywords: curcumin; COVID-19; nucleocapsid phosphoprotein; membrane glycoprotein; antiviral mechanism
Online: 7 June 2020 (17:21:49 CEST)
Corona virus disease 2019 (COVID-19) is caused by a Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2), which is a positive strand RNA virus. The SARS-CoV-2 genome and its association to SAR-CoV-1 vary from ca. 66% to 96% depending on the type of betacoronavirdeae family members. With several drugs, viz. chloroquine, hydroxychloroquine, ivermectin, artemisinin, remdesivir, azithromycin considered for clinical trials, there has been an inherent need to find distinctive antiviral mechanisms of these drugs. Curcumin, a natural bioactive molecule has been shown to have a therapeutic potential for various diseases, but its effect on COVID-19 has not been explored. In this study, we show the binding potential of curcumin targeted to a variety of SARS-CoV-2 proteins, viz. spike glycoproteins (PDB ID: 6VYB), nucleocapsid phosphoprotein (PDB ID: 6VYO), membrane glycoprotein (PDB ID: 6M17) along with nsp10 (PDB ID: 6W4H) and RNA dependent RNA polymerase (PDB ID: 6M71) structures. Our results indicate that curcumin has high binding affinity towards nucleocapsid and nsp 10 proteins with potential antiviral activity.
ARTICLE | doi:10.20944/preprints202003.0130.v1
Subject: Materials Science, Biomaterials Keywords: liposomes; polymersomes; filtration; freeze-thaw; membrane mechanics; encapsulation stability
Online: 8 March 2020 (04:23:34 CET)
Sterilisation and preservation of vesicle formulations are an important consideration for their viable manufacture for industry applications, particular those intended for medicinal use. Here we undertake an initial investigation of the stability of hybrid lipid – block copolymer vesicles to common sterilisation and preservation processes, with particular interest in how the block copolymer component might tune vesicle stability. We investigate two sizes of polybutadiene-block-poly(ethylene oxide) polymers (PBd12-PEO11 and PBd22-PEO14) mixed with the phospholipid POPC considering the encapsulation stability of a fluorescent cargo and the colloidal stability of vesicle size distributions. We find that autoclaving and lyophilisation cause complete loss of encapsulation stability under the conditions studied here. Filtering through 200 nm pores appears to be viable for sterilisation for all vesicle compositions with comparatively low release of encapsulated cargo, even for vesicle size distributions which extend beyond the 200 nm filter pore size. Freeze-thaw of vesicles also shows promise for preservation of hybrid vesicles with high block copolymer content. We discuss the process stability of hybrid vesicles in terms of the complex mechanical interplay between bending resistance, stretching elasticity and lysis strain of these membranes and propose strategies for future work to further enhance the process stability of these vesicle formulations.
ARTICLE | doi:10.20944/preprints201810.0758.v1
Subject: Biology, Plant Sciences Keywords: latent PPO; optimisation; peripheral membrane POD; total phenol content
Online: 1 November 2018 (18:00:20 CET)
The present protocol described extraction of active polyphenol oxidase and peroxidase from a plant rich in phenolics and chlorophylls in the post-harvest browning syndrome of B. myrtifolia. Initially, general optimisation using conventional enzyme extractions was performed. However, along with membrane-bound proteins, chlorophylls and phenols were also released with Triton X (TTX). With a view to obtaining high enzymatic activity, removal of the released chlorophylls and phenols by formation of TTX-114 micelles in the detergent rich phase after high-temperature induced phase separation was tested.
ARTICLE | doi:10.20944/preprints201807.0356.v1
Subject: Physical Sciences, Other Keywords: Anomalous diffusion; FRAP; Numerical Simulations; PH -domain, Membrane Binding
Online: 19 July 2018 (11:17:03 CEST)
FRAP technique have been used for decades to measure movements of molecules in 2D. Data obtained by FRAP experiments in cell plasma membranes are assumed to be described through means of two parameters, a diffusion coefficient D (as defined in a pure Brownian model) and a mobile fraction M. Nevertheless, it has also been shown that recoveries can be nicely fit using anomalous sub-diffusion. FRAP at variable radii has been developed using the Brownian diffusion model to access geometrical characteristics of the surrounding landscape of the molecule. Here we performed numerical simulations of continuous time random walk (CTRW) anomalous subdiffusion and interpreted them in the context of variable radii FRAP. These simulations were compared to experimental data obtained at variable radii on living cells using the PH domain of the membrane binding protein EFA6 (exchange factor for ARF6, a small G protein). This protein domain is an excellent candidate to explore the structure of the interface between cytosol and plasma membrane in cells. By direct comparison of our numerical simulations to the experiments, we show that this protein does not exhibit anomalous diffusion in BHK cells. The non Brownian PH-EFA6 dynamics observed here is more related to spatial heterogeneities such as cytoskeleton fences effects.
Subject: Engineering, Automotive Engineering Keywords: MASM; new model for membrane activated sludge system; super-fast membrane activated sludge; particle size distribution; modified COD fractionation; captured COD fractions.
Online: 26 April 2021 (13:01:21 CEST)
The structure of existing activated models is inherently deficient in reflecting the major role of the membrane filtration. This study developed and proposed a novel model, MASM, for the membrane activated process. The effective filtration size imposed by the membrane module, entrapping larger size particles was adopted as the basis of the proposed model. The model defined a modified COD fractionation, accounting for the captured COD fractions as additional model components and utilizing related mass balance relationships. It was implemented for testing the fate of soluble hydrolysable COD and system performance of super-fast membrane activated sludge based on real data for the characterization and process kinetics of domestic sewage and denim processing effluents. Model evaluation was carried for parallel systems with gravity settling and membrane filtration operated at a sludge age range of 0.5-2.0 d. Results reflected significantly better performance of super-fast membrane activated sludge system for both wastewaters, underlining that it was crucially important to account for the captured COD fractions to provide an accurate evaluation of system behavior and effluent quality. This should also be identified as the major shortcoming of the ASM models for evaluating and predicting system performance of activated sludge configurations with membrane separation.
CASE REPORT | doi:10.20944/preprints202209.0035.v2
Subject: Life Sciences, Biotechnology Keywords: Chronic Venous Insufficiency; Venous Leg Ulcer; Dehydrated Amniotic Membrane Allograft
Online: 5 September 2022 (10:57:27 CEST)
Chronic venous insufficiency (CVI) is a lifelong, moribund, and debilitating disease process with tremendous personal and financial costs. At its core, CVI involves blood pooling in the lower extremities secondary to inadequate venous blood return, resulting in venous hypertension and incompetence of the one-way valves in the lower extremity veins. As venous circulation slows, metabolic demands of the cells in the lower extremities increase, leading to stasis dermatitis, infection, cellular death, and venous ulceration. This case study aims to report the efficacy of dehydrated amniotic membrane allograft (DAMA) applications to a chronic right lateral ankle ulcer resulting from chronic venous insufficiency. The patient in this study received DAMA applications weekly for six weeks. Upon examination at the initial application, the wound was wet and macerated due to drainage with significant hemosiderosis and lipodermatosclerosis consistent with a Venous Clinical Severity Score (VCSS) of 2. Upon inspection at the final visit, the wound was closed, with a VCSS of 0. This case study demonstrates that the application of DAMA has the potential to act as an effective barrier to cover and accelerate wound closure time. Future non randomized and randomized controlled trials may further establish standardized protocols for DAMA application in venous ulceration, help create treatment algorithms to predict wound closure endpoints, and encourage innovation that may further accelerate healing time.
REVIEW | doi:10.20944/preprints202208.0248.v1
Subject: Biology, Physiology Keywords: action potential; soliton/wave; lipid phase transition; scientific method; membrane
Online: 15 August 2022 (04:27:26 CEST)
This article is a followup to an earlier review which outlined some of the interesting features of the soliton/wave-action potential (AP) model, and noted the need to test its key aspects; including the need to test if its presumed lipid phase transition is actually happening during AP firings in excitable cells. The intent here is to point out the sort of tests, and evidence from them, that might be needed if the soliton/wave-AP model is to be accepted broadly by biologists. Here, after an overview of the modern electrophysiological-AP model and of the soliton/wave-AP model, there are three areas considered. First, possible compositional influences on membrane properties relative to the soliton/wave-AP model are presented. Including questions with regard to the soliton/wave-AP model’s assumption that changes in surface potentials influence the transmembrane potential. Second, some recent work from the good folks who advocate for the soliton/wave-AP model concerning the occurrence of lipid phase transitions in neurons or in extracts from nervous tissues are examined. Here it is noted that there is a need to consider whether these lipid phase transitions happen within normal physiological conditions or not. Third, and finally, the advocates for the soliton/wave-AP model have adopted a thermodynamic/theory-based philosophical approach in their studies. It is argued that this philosophical approach is a radical departure from the philosophical approach used under the scientific method. The features of this new approach, and implications its use, are examined.
ARTICLE | doi:10.20944/preprints202206.0187.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: Membrane fouling; Hermia model; Fouling model; Pore blocking; Blocking mechanism
Online: 13 June 2022 (12:54:53 CEST)
One of the most broadly used models for membrane fouling is the Hermia model, which separates this phenomenon into four blocking mechanisms, each with an associated parameter n. These mechanisms are complete blocking (n=2), intermediate blocking (n=1), standard blocking (n=3/2) and cake formation (n=0). The original model, which was obtained through experimental data, is given by an Ordinary Differential Equation (ODE) dependent on n. At the time, this ODE was only solved for these four values of n, which limits the effectiveness of the model when adjusted to experimental data. The aim of this paper is to not only mathematically prove the original Hermia model, but also to broaden the scope of this model for any real number n by using the original ODE, the equations of fluid mechanics and the properties of single and multivariable calculus. The final generalized Hermia model is given by a power-law for any n≠2 and is given by an exponential function at n=2 and can be fitted to ultrafiltration, microfiltration, nanofiltration and reverse osmosis data with acceptable values of R2 (>0.93). Here it is also shown that the accumulated volume as a function of time follows the same type of ODE. The values of n between the four original discreate values could be physically interpreted as the existence of new blocking mechanisms.
ARTICLE | doi:10.20944/preprints202205.0200.v1
Subject: Life Sciences, Biophysics Keywords: membrane potential; Nernst equation; ion adsorption; surface charge; surface potential
Online: 16 May 2022 (08:12:52 CEST)
Although there is a common physiological notion that the origin of the membrane potential is attributed to transmembrane ion transport, it is theoretically possible to explain its generation by the mechanism of ion adsorption. It was previously suggested that the ion adsorption mechanism led even to the potential formulas which are even identical to either the famous Nernst equation or Goldman-Hodgkin-Katz equation. Our further analysis shown in this paper indicates that the potential formula based on the ion adsorption mechanism leads to one equation which is the function of material surface charge density and the material surface potential. Furthermore, we confirmed that the equation holds in all the different experimental systems we studied. Although we have not succeeded in elucidating why such an equation is established, the equation appears to be the key equation governing the characteristics of the membrane potential regardless of the systems in question.
ARTICLE | doi:10.20944/preprints202205.0055.v1
Subject: Chemistry, Physical Chemistry Keywords: ion exchange membrane; diffusion permeability; weak electrolyte; ammonium chloride; simulation
Online: 5 May 2022 (16:49:08 CEST)
It is known that ammonium has a higher permeability through anion-exchange and bipolar membranes compared to K+ cation that has the same mobility in water. However, the mechanism of this high permeability is not clear enough. We develop a mathematical model based of the Nernst-Planck and Poisson equations for diffusion of ammonium chloride through an anion-exchange membrane; proton exchange reactions between ammonium, water and ammonia are taken into account. It is assumed that ammonium, chloride and OH− ions can only pass through membrane hydrophilic pores, while ammonia can also dissolve in membrane matrix fragments not containing water and diffuse through these fragments. It is found that due to the Donnan exclusion of H+ ions as coions, the pH in the membrane internal solution increases when approaching the membrane side facing distilled water. Consequently, there is a change in the principal nitrogen-atom carrier in the membrane: in the part close to the side facing the feed NH4Cl solution (pH<8.8), it is the NH4+ cation, and in the part close to distilled water, NH3 molecules. The concentration of NH4+ reaches almost zero at a point close to the middle of the membrane cross-section, which approximately halves the effective thickness of the diffusion layer for the transport of this ion. When NH3 takes over the nitrogen transport, it only needs to pass through the other half of the membrane. Leaving the membrane, it captures an H+ ion from water, and the released OH− goes towards the membrane side facing the feed solution to meet the NH4+ ions. The comparison of the simulation with experiment shows a satisfactory agreement.
ARTICLE | doi:10.20944/preprints202204.0038.v1
Subject: Biology, Physiology Keywords: Goldman-Hodgkin-Katz eq.; Nernst eq.; ion adsorption; membrane potential
Online: 6 April 2022 (08:37:53 CEST)
Current physiology attributes the mechanism of membrane potential generation to transmembrane ion transport, but ion adsorption could just as well play this fundamental role. The evidence shows that the ion adsorption mechanism accurately reproduces the experimentally measured membrane potential. The Goldman-Hodgkin-Katz equation (GHK eq.) and the Nernst equation (Nernst eq.) are the typical mathematical formulas representing the membrane potential in current physiology. However, the authors were able to show that the potential formulas by ion adsorption mechanism give identical results to GHK eq. and Nernst. eq. Our experimental and theoretical analyses suggest that there is a special relationship between the membrane potential and the membrane surface charge density, and this unique equation inevitably leads to the establishment of a GHK eq and/or a Nernst eq. The authors found that the unique equation is the foundation of thermodynamics “Boltzmann distribution”. Thus, the GHK eq. and the Nernst eq. are simply the natural consequence of thermodynamics from the view of the ion adsorption mechanism.
ARTICLE | doi:10.20944/preprints202105.0159.v1
Subject: Physical Sciences, Acoustics Keywords: osmotic membrane; Polydimethylsiloxane; saline droplet; mass transport; evaporation; reversible cycle.
Online: 10 May 2021 (10:23:50 CEST)
We report cyclic growth/retraction phenomena observed for saline droplets placed on the cured PDMS membrane with the thickness of 7.8±0.1 µm floating on pure water surface. Osmotic mass transport across the micro-scaled floating PDMS membrane provided the growth of the sessile saline droplets followed by evaporation of the saline droplets. The observed growth/retraction cycle was reversible. The model of the osmotic mass transfer across the cured PDMS membrane is suggested. The model explains semi-quantitatively the time evolution of a droplet.
ARTICLE | doi:10.20944/preprints202012.0432.v1
Subject: Life Sciences, Biochemistry Keywords: pomegranate; antioxidant capacity; membrane vesicles; cauliflower; keratinocytes; oxidative stress; cytotoxicity
Online: 17 December 2020 (12:05:42 CET)
Pomegranate extract (PG-E) has been reported to exert a protective effect in skin due to its antioxidant activity. Ingredients rich in phenolic compounds are unstable in extract solutions and, therefore, the use of a suitable nanosystem to encapsulate this type of extract could be necessary in different biotechnological applications. Thus, we investigated the capacity of Brassica oleracea L. (cauliflower) inflorescence vesicles (CI-vesicles) to encapsulate PG-E and determined the stability and the antioxidant capacity of the system over time. In addition, the protective effect against UV radiation and heavy metals in HaCaT cells was also tested. The CI-vesicles had an entrapment efficiency around 50% and accelerated stability tests did not show significant changes in the parameters tested. The results for the HaCaT cells show the non-cytotoxicity of the CI-vesicles containing PG-E and their protection against heavy metals (lead acetate and mercuric chloride) and UV-B radiation through a reduction of oxidative stress. The reduction of the percentage of deleted mtDNA (mtDNA4977, “common deletion”) in UV-treated HaCaT cells due to the presence of CI-vesicles containing PG-E indicates the mechanism of protection. Therefore, the effects of CI-vesicles loaded with PG-E against oxidative stress support their utilization as natural cosmeceuticals to protect skin health against external damage from environmental pollution and UV radiation.
ARTICLE | doi:10.20944/preprints202011.0371.v1
Subject: Chemistry, Analytical Chemistry Keywords: membrane transport; A327H+Cl- ionic liquid; gold; hydrochloric acid; nanoparticles.
Online: 13 November 2020 (10:57:44 CET)
By the use of the tertiary amine A327 and 1 M HCl solution as precursors, the ionic liquid A327H+Cl- was generated and used to investigate its performance in the transport of Au(III) form hydrochloric acid medium. The influence of the stirring speed (600-1800 min-1), ionic liquid concentration (1.25-50% v/v) in the membrane phase and gold concentration (0.01-0.15 g/L) in the feed phase on metal transport have been investigated. An equation which included both equilibrium and kinetics parameters was derived, and the membrane diffusional resistance (Δm) and feed phase diffusional resistance (Δf) was estimated as 9.5x106 s/cm and 307 s/cm, respectively. At carrier concentrations in the 5-50% v/v range and gold concentrations in the 0.01-0.15 g/L range, metal transport is controlled by diffusion of metal species through the feed boundary layer, whereas at the lowest carrier concentrations, membrane diffusion is predominant. From the receiving solutions, gold can be recovered as gold nanoparticles.
ARTICLE | doi:10.20944/preprints202009.0325.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: Keywords; CO2; conversion; bibliometrics; electrode design; CO2RR; membrane; flow cell
Online: 15 September 2020 (04:45:17 CEST)
The chemistry and electrochemistry basic fields have been active since the last two decades of the past century studying how surface modification of electrodes by coating with conductive films enhances their activity and performance. In the light of the development of alternative sustainable ways of energy storage and carbon dioxide conversion by electrochemical processes, these research studies have jumped in the 21st century to more applied fields such as chemical engineering, energy and environmental science and engineering. The huge amount of literature on experimental works dealing with the development of CO2 electroreduction processes addresses electrocatalyst development. Membranes can help understanding and controlling the mass transport limitations of current electrodes and reactors designs. The present bibliometric review addresses the papers published in the 21st century regarding membrane coated electrodes and electrocatalysts to enhance electrochemical reactor performance and viability with a special focus on the urgent issue of carbon dioxide capture and utilization.
Subject: Life Sciences, Microbiology Keywords: Klebsiella pneumoniae; nonmucoid; O-antigen; outer membrane protein; phage receptor
Online: 25 July 2020 (18:55:02 CEST)
The use of bacteriophage is reemerging as a tool for combatting multi-drug resistant bacterial infections. In our previous study, we showed that colistin resistant carbapenem-resistant Klebsiella pneumoniae (ColR-CRKP) is more susceptible to killing by lytic tailed phages, including ФNJS1 specific for nonmucoid K. pneumoniae. Although we demonstrated that alteration on surface charges of ColR-CRKP promotes phage adherence and infection, the receptor for ФNJS1 was still unknown. In current study, we identified O-antigen was involved in the reversible adsorption, and outer membrane protein (OMP) FepA may be served as one of the irreversible receptors for ФNJS1. We firstly found accelerated reversible phage adsorption to ColR-CRKP cells, and that periodate treatment of bacteria inhibited the phage binding, indicating LPS may be involved in phage reversible adsorption. ФNJS1-resistant bacterial mutants screening revealed that mutants in ∆wecG(mTn5) and ∆wecA(mTn5), two genes responsible for LPS biosynthesis, affected phage adsorption capacity and phage infectivity. The loss of wzyE encoding O-antigen polymerase showed no significant difference in phage adsorption but increased phage infectivity, suggesting the long chain length of O-antigen may also be a barrier for bacteriophage infection. Among four OMP mutants including ∆fepA, ∆fhuA, ∆ompA and ∆ompC, only ∆fepA slowed phage lysis rate, suggesting FepA may be as one of irreversible receptors for ФNJS1. The results are helpful to better understand why ColR-CRKP sensitizes phage infection and to combat multi-drug resistant K. pneumoniae infections in the future.
Subject: Life Sciences, Biochemistry Keywords: Lipidomics; ssRNA+ virus; membrane fusion; lipid metabolism; cholesterol; sphingolipids; phosphatidylinositol
Online: 17 July 2020 (14:01:21 CEST)
Recent COVID-19 outbreak has come into prominence the pathogenetic mechanisms underlying the Biology and Biochemistry of viral infections. COVID-19 illness is brought about by infection with the severe acute respiratory syndrome coronavirus SARS-CoV-2 [1,2], an enveloped positive single stranded RNA virus (ssRNA+). From a lipidomics viewpoint, there is a variety of mechanisms involving virus infection that encompass virus entry, disturbance of host cell lipid metabolism, and the role played by diverse lipids in regard to the infection effectiveness. All these aspects have currently been tackled separately as independent issues and focusing on the function of proteins. Here we review the role of cholesterol and other lipids in in ssRNA+ and SARS-COV-2 infection.
REVIEW | doi:10.20944/preprints202005.0518.v1
Subject: Life Sciences, Biophysics Keywords: virus; extracellular vesicles; COVID-19; SARS-CoV-2; membrane vesicluation
Online: 31 May 2020 (21:35:23 CEST)
Within the micro and nano world, tiny membrane-enclosed bits of material are more or less free to move and act as communication tools within cells, between cells, between different tissues and between organisms in global environment. Based on the mechanism of membrane budding and vesiculation that includes all types of cells, in this review, we attempted to present a review on SARS-CoV-2 virus actions in compartments of different scales (cells and their surroundings, tissues, organisms and society). Interactions of the virus with cells on a molecular level, with neural system, endothelium, hematopoietic system, gastrointestinal system and genitourinary system. Transmission route between organisms and between mother and fetus are considered. Also, transmission of virus through contact with materials and with environment, the suggested measures to prevent contamination with the virus and to support the organism against the disease are given.
REVIEW | doi:10.20944/preprints202003.0047.v1
Subject: Medicine & Pharmacology, Dentistry Keywords: socket shield; dental Implants; root membrane; buccal shield; aesthetic zone
Online: 4 March 2020 (04:45:00 CET)
There are different treatment options in modern dentistry for the replacement of lost dentition. Of these the most upcoming and acceptable treatment option is Dental implants. The common problem usually with immediate implant placement in the anterior region is the post-operative soft tissue contour as a part of the bone modelling during healing. Hurzeler et al in 2010 introduced a new technique called the “socket shield technique”. This technique has been used as an alternative treatment modality for immediate implant placement in the aesthetic zone.This review articles provides a detailed information regarding the clinical concept of Root membrane technique.
ARTICLE | doi:10.20944/preprints202001.0262.v1
Subject: Materials Science, Metallurgy Keywords: indium(III); ionic liquid; supported, liquid membrane; Hostarex A324; transport
Online: 23 January 2020 (04:07:43 CET)
The transport of indium(III), from HCl solutions, across a supported liquid membrane in flat-sheet configuration was investigated, being the carrier the ionic liquid HA324H+Cl- (derived from the tertiary amine Hostarex A324 and hydrochloric acid). Different variables affecting the metal transport: hydrodynamic conditions in the source and receiving phases, metal and HCl concentrations in the source phase, and carrier concentration in the membrane phase, were investigated. Also the transport of indium(III) using carriers of various nature: ionic liquids, alcohol, ketone, phosphine oxide and phosphoric ester, was compared. The metal transport was modelled describing the transport mechanism as: diffusion across the source diffusion layer, a fast interfacial chemical reaction, and diffusion of the InCl4--carrier complex through the membrane support. Diffusional parameters for the transport of indium(III), from the experimental data and the model, were estimated.
Subject: Engineering, Civil Engineering Keywords: geometric nonlinearity; improved multis-cale method; orthotropic membrane; aeroelastic instability
Online: 11 July 2019 (09:02:13 CEST)
Membrane materials are most widely applied in construction engineering with small mass and high flexibility, it presents strong geometric nonlinearity in the process of vibration. In the paper, an improved multi-scale perturbation method is used to solve the aeroelastic stability of closed and open membrane roofs for quantify the effect of geometric nonlinearity on the single-mode aeroelastic instability wind speed of membrane roofs. The results show that the critical wind speed values of the two models are small when the geometrical nonlinearity of membrane material is neglected. In addition, under normal wind load, the influence of geometrical nonlinearity of membrane on the aerodynamic stability of roof can be neglected, However, under strong wind load, when the roof deformation reaches 3% of the span, the influence of geometric nonlinearity should be considered and the influence increases with the decrease of transverse and downwind span of membrane roof. The results obtained in this paper have important theoretical reference value for the design the membrane structures.
COMMUNICATION | doi:10.20944/preprints201904.0151.v1
Subject: Materials Science, Biomaterials Keywords: ISFETs; ISE; polyurethane; salivary nitrate; stress; drift; ion-selective membrane
Online: 13 April 2019 (05:06:44 CEST)
We have studied on the stress measurement by making use of salivary nitrate, which can be a candidate of stress markers, with ion-selective field-effect transistors (ISFETs). ISFETs are suitable for on-site single-drop analysis of salivary nitrate within 10 seconds. However, when ISFETs are used for salivary nitrate, ISFETs have a problem which is called the initial drift. The initial drift makes it difficult for determination of an accurate nitrate monitoring. Thus, the purpose of this study is to suppress an initial drift and to search for new easy polymer to possess more performance of sensor responses than conventional matrix membrane such as PVC. In this research, we investigated ISFETs using specific matrix membrane for example, KP-13, Pellethane® and P7281-PU. The initial drift was evaluated from the fluctuation of the response values generated by ISFETs which are immersed in saliva or aqueous solution. As a result, P7281-PU showed its suppression effect for the initial drift in the whole saliva and various solutions. Furthermore, the cause of drift may be H+ diffusion, and drift suppression effect of P7281-PU may be affected by urethane bond capturing H+ in ion-selective membrane. This result suggests a continuous nitrate monitoring and development of wearable sensors.
ARTICLE | doi:10.20944/preprints201806.0187.v1
Subject: Chemistry, Chemical Engineering Keywords: membrane bioreactor (MBR); wastewater; rotating membranes; static membranes; fouling; modelling
Online: 12 June 2018 (10:48:01 CEST)
Fouling by activated sludge in membrane bioreactor (MBR) processes for wastewater treatment can be reduced using several strategies such as backflushing, relaxation, and chemical cleaning. Some proprietary systems such as Avanti’s RPU-185 Flexidisks MBR use novel circular rotating, flat sheet membranes to assist in limiting this fouling. An attempt has already been made to model this novel rotating fouling process by developing a simulation model based on first principles and traditional fouling mechanisms. In order to directly compare the potential benefits of rotational MBR system, a follow-up study was carried out using Avanti’s newly developed static (non-rotating) Flexidisks MBR system. This new process uses the same proprietary and patented membrane modular arrangement as used in the circular rotational unit, but is configured instead as a static square-shaped unit which is in-line with the more traditional and popular format used for submerged flat sheet MBR systems. During this study, the results from operating the static pilot unit were simulated and modelled using a standard fouling model coupled with a viscosity to mixed liquor relationship model. These results were then compared with those obtained from running the rotating MBR model however with rotational switching functions turned off and rotational parameters set to a static mode. This comparison was done to ascertain whether the basic premise of the developed rotational model was sound in empirical terms when compared to a standard MBR flux model. The study concluded that relatively good agreement was reached between the two types of models, thus vindicating the usage of a complex rotational MBR model. Follow on studies will now compare results from the rotating MBR system using rotational models developed by other researchers to ascertain the effectiveness rotating MBR modelling approach.
ARTICLE | doi:10.20944/preprints201804.0356.v1
Subject: Medicine & Pharmacology, Other Keywords: animal model; chronic tympanic membrane perforation; mitomycin C; myringotomy; dexamethasone
Online: 27 April 2018 (08:36:00 CEST)
Background. A rat model of chronic tympanic membrane perforation was developed to be used in the search of new materials for the sealing of these perforations. Methods. A longitudinal study was carried out in rats subjected to incisional myringotomy followed by the application of mitomycin C alone or with dexamethasone. Rats were checked at days 3, 7, 10, 14 and weekly thereafter until perforation closure, for up to 6 months. Results. The addition of dexamethasone is a key component in order to obtain a chronic opening. Myringotomies treated with saline had a mean healing time of 8.5 days. At 8 weeks, 70.5% of these remained perforated and at 6 months this number fell to 21.4%. Conclusion. This technique is able to maintain more than 70% of tympanic membrane perforations patent for at least 8 weeks. This rat model is adequate for its use in preclinical or translational research.
ARTICLE | doi:10.20944/preprints202204.0069.v2
Subject: Medicine & Pharmacology, Gastroenterology Keywords: hepatocellular carcinoma; conventional transarterial chemoembolization; emulsion; lipiodol; glass membrane emulsification device
Online: 6 June 2022 (05:53:21 CEST)
Background: Transarterial chemoembolization (TACE) is the standard treatment for BCLC-B hepatocellular carcinoma (HCC). A novel glass membrane emulsification device (GMD) produces a high percentage of water/oil emulsions with homogeneous and stable droplets. There are few reports on the efficacy of GMD-conventional-TACE (GMD-c-TACE)；therefore, we aimed to evaluate the effectiveness of GMD-c-TACE. Methods: Seventy-one patients with HCC with tumor diameter <5 cm who underwent c-TACE with and without GMD were included in this study to investigate local recurrence and hepatic functional reserve. Results: The local recurrence rates of TACE without GMD were 3.0% at 6 months, 16.7% at 12 months, and 35.0% at 18 months, around where it plateaued. Hence, the local recurrence rates in the GMD-c-TACE group were 7.7% at 14 months and 23.1% at 20 months, respectively. Thus, GMD-c-TACE had a significantly lower local recurrence. Multivariate analysis showed that GMD-c-TACE could suppress local recurrence and maintain hepatic reserve. Conclusions: GMD-c-TACE allows dense lipiodol accumulation in the tumor and attainment of good local control. Additionally, the inhibition of the release of anticancer drugs may maintain hepatic reserve. GMD-c-TACE is useful in preventing local recurrence and is expected to become the standard treatment form of c-TACE in the future.
ARTICLE | doi:10.20944/preprints202201.0392.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: Pterygium; Pterygium surgery; Amniotic membrane; Conjunctival auto-graft; Polish Caucasian population
Online: 26 January 2022 (11:54:17 CET)
This study compares the efficacy of the two most commonly used surgical methods for pterygium in the Polish population, conjunctival autograft versus amniotic membrane transplantation, and to evaluate the postopera-tive recurrence rate. We retrospectively analysed the medical records of 65 patients who underwent surgery for primary or recurrent pterygium at an ophthalmology clinic in Bialystok, Poland between 2016 and 2020. Surgical success (no regrowth) occurred in almost half of the amniotic membrane patients (44%) and in most of the conjunctival autograft patients (79%); this was a significant relationship. The odds of successful surgery were 79% lower for subjects with amniotic membranes than for those with conjunc-tival autografts (OR with 95% CI = 0.21 (0.05; 0.94]; p = 0.045). Our study confirms that in Polish Caucasian population the success rate of the pro-cedure using conjunctival autograft versus the use of amniotic membrane, is in favoured for the procedure with conjunctival graft.
ARTICLE | doi:10.20944/preprints202112.0496.v1
Subject: Chemistry, Physical Chemistry Keywords: Calcium channel; gating modifier; SNX-482; cysteine-rich peptide; Membrane partitioning
Online: 31 December 2021 (09:35:18 CET)
Spider toxin SNX-482 is a cysteine-rich peptide that interferes with calcium channel activity by binding to voltage-sensing domains of CaV2.3 subtype. Two general binding mechanisms are present in nature: direct binding from the aqueous phase or through lateral diffusion from the membrane, the so-called reduction in dimensionality mechanism. In this work, via coarse-grained and atomistic molecular dynamics simulations, we have systematically studied the spontaneous partitioning of SNX-482 with membranes of different anionic compositions and explored via diffusional analysis both binding mechanisms. Our simulations revealed a conserved protein patch that inserts within the membrane, a preference for binding towards partially negatively charged membranes, and that electrostatics drives membrane binding. Finally, diffusivity calculations showed that the toxin diffusion along the membrane plane is an order of magnitude slower than the aqueous phase suggesting that the critical factor in determin-ing the SNX-482-CaV2.3 binding mechanism is the affinity between the membrane and SNX-482
BRIEF REPORT | doi:10.20944/preprints202109.0038.v1
Subject: Life Sciences, Virology Keywords: Membrane fusion; gp120; gp41; bnAb; CD4; virus-cell fusion; syncytium formation
Online: 2 September 2021 (12:13:53 CEST)
PG9, PG16, PGT121, and PGT145 antibodies were identified from culture media of activated memory B-cells of an infected donor and shown to neutralize many HIV-1 strains. Since HIV-1 spreads via both free virions and cell-cell fusion, we examined the effect of the antibodies on HIV-1 Env-mediated cell-cell fusion. Clone69TRevEnv cells that express Env in the absence of tetracycline were labeled with Calcein-AM Green, and incubated with CD4+ SupT1 cells labeled with CellTrace™ Calcein Red-Orange, with or without antibodies. Monoclonal antibodies PG9, PG16, 2G12, PGT121, and PGT145 (at up to 50 µg/mL) had little or no inhibitory effect on fusion between HIV-Env and SupT1 cells. By contrast, Hippeastrum hybrid agglutinin completely inhibited fusion. Our results indicate that transmission of the virus or viral genetic material would not be inhibited by these broadly neutralizing antibodies. Thus, antibodies generated by HIV-1 vaccines should be screened for their inhibitory effect on Env-mediated cell-cell fusion.
ARTICLE | doi:10.20944/preprints202107.0540.v1
Subject: Biology, Anatomy & Morphology Keywords: polymeric spiral-wound membrane; microfiltration; transmembrane pressure; diafiltration; micellar casein concentrate
Online: 23 July 2021 (11:05:17 CEST)
Micellar Casein Concentrate (MCC) is manufactured from microfiltration (MF) of skim milk utilizing ceramic or polymeric membrane filtration. While ceramic filtration has higher efficiency, use of polymeric is cost effective and the process is familiar to several US dairy processors. The aim of the present study was to develop an optimized membrane filtration process to produce MCC using spiral wound polymeric membrane filtration (SW MF) system by systematic selection of transmembrane pressure (TMP) and level of diafiltration (DF). Using skim milk as feed material, preliminary lab-scale MF experiments were conducted using 0.5 µm polyvinylidene fluoride (PVDF) membrane. Three TMP (34.5, 62.1, and 103.4 kPa) and three levels of DF (70, 100, and 150%) along with a process without DF as control were used in the study. Effect of TMP and effectiveness of DF on flux rates, SP removal, casein to total protein (CN/TKN) ratio, casein to true protein (CN/TP) ratio, rejection of casein (rej CN) and SP (rej SP) were evaluated. At all TMP values used in the study, the overall flux (O Flux) increased with the level of DF. Highest O Flux of 30.77 liter per meter square per hour (LMH) was obtained with 34.5 kPa pressure and 150% DF. The impact of DF was more pronounced at lower pressures than at the higher pressures used in the study. With controlled DF, instantaneous flux was maintained within 80% of initial flux for the entire process run. For all the experiments, casein has a rejection of 0.97 to 1.0, while serum protein has the lowest rejection of 0.10 at 34.5 kPa pressure and 150% DF level. Use of 34.5 kPa and DF level of 150 % contributed to 81.45% SP removal, and casein to true protein ratio of 0.96. SP removal data from the lab-scale experiments were fitted into a mathematical model using DF and square of TMP as factors. The model predicts SP removal within 90-95% of actual SP removal got from the pilot plant experiments.
ARTICLE | doi:10.20944/preprints202106.0356.v1
Subject: Life Sciences, Biochemistry Keywords: cell model; Bernstein; Nernst equation; membrane potential; GHK equation; HH model
Online: 14 June 2021 (11:50:34 CEST)
The cellular model we teach and have theorized assumes that the cell is the basic unit of multicellular living beings. This fundamental element has been the subject of many theories concerning its properties and the exchanges that exist with its environment. In this article, we demonstrate that certain functional aspects, in particular the electrical aspects related to diffusion, have not been correctly assumed or that certain initial conditions have been purely ignored and are in contradiction with physics, chemistry and thermodynamics.
ARTICLE | doi:10.20944/preprints202012.0725.v1
Subject: Medicine & Pharmacology, Allergology Keywords: extracorporeal membrane oxygenation; meconium aspiration syndrome; neonate; Hub and Spoke; outcomes
Online: 29 December 2020 (09:29:49 CET)
The neonatal Hub and Spoke (HandS) ECMO approach provides emergent ECMO implantation to support neonates in severe cardio-respiratory life-threatening conditions at secondary (Spoke) centers, and a safe transfer to the ECMO center (Hub). We report a retrospective review of 11 neonates fom January 2014 to January 2020, presenting with life-threatening conditions and treated by HandS ECMO team in Spoke hospitals. Protocols and checklists were arranged by a local group of ECMO experts and shared with all the hospitals located in North-Eastern Italy. At the emergent call, all patients were cared for at the Spoke hospitals, receiving maximal respiratory and cardiovascular support (including high frequency oscillatory ventilation, inhaled nitric oxide, and major inotropic intravenous infusion). All but 3 patients were affected by life-threatening meconium aspiration syndrome. Median duration of ECMO support and hospitalization were 4 days (range 2-32) and 30 days ( range 8-50), respectively. All but 2 patients with congenital diaphragmatic hernia, were weaned off ECMO and discharged home without complications. At a median follow up of 14.4 months (1.3-74.8), all survivors were alive and in good clinical conditions, without medications, and normal somatic growth. All but one had normal neuropsychological development. We conclude that HandS ECMO model for treating neonates in life-threatening conditions is effective and successful. A specialized multidisciplinary team and common organizational protocols shared between Hub and Spoke centers are the key-points for success. While excellent results occur with MAS (100% survival), treatment was not successful in CDH, in which other that HandS ECMO issues are implied. Lessons learned from our experience are presented and discussed in this article.
ARTICLE | doi:10.20944/preprints202009.0267.v3
Subject: Engineering, Automotive Engineering Keywords: mechanical characterization; foams; ultrafiltration membrane; finite element method; non-linear deformations
Online: 15 October 2020 (16:48:45 CEST)
To investigate the effect of Polyvinylpyrrolidone (PVP) addition and consequently porosity, two different sets of membranes are manufactured, since PVP is a widely used poring agent which has an impact on the mechanical properties of the membrane material. The first set (PAN 1) includes PAN and the necessary solvent while the second set (PAN 2) is made of PAN and PVP. These membranes are put through several characterisation processes including tensile testing. The obtained data are used to model the static behaviour of the membranes with different geometries, but similar loading and boundary conditions that represent their operating conditions. This modelling process is undertaken by using finite element method. The main idea is to investigate how geometry affects the load-carrying capacity of the membranes. Alongside membrane modelling, their materials are modelled with representative elements with hexagonal and rectangular pore arrays (RE) to understand the impact of porosity on the mechanical properties. Exploring the results, the best geometry is found as the elliptic membrane with the aspect ratio 4 and the better RE as the hexagonal array which can predict the elastic properties with an approximate error of 12%.
ARTICLE | doi:10.20944/preprints202010.0259.v1
Subject: Biology, Anatomy & Morphology Keywords: spring water; karst; 16S rRNA gene; membrane filters; metabarcoding; pathogenic bacteria
Online: 12 October 2020 (17:39:14 CEST)
(1) Introduction: Karstic springs are used worldwide by rural communities as sources of fresh water for human use and livestock survival. In Romania, 1/3 of the population has no direct access to the public water supply. The present study is part of a country-wide project on developing simple, quick and cheap methods for seasonal environmental and microbiological monitoring of karstic springs used as drinking water supply by rural populations. Critical steps for the monitoring workflow consist in the evaluation of water quality and choosing of suitable membrane filters to efficiently capture environmental DNA for further microbial diversity estimation by 16S rRNA gene-based metabarcoding; (2) Methods: Several commercial membrane filters of different composition and pore sizes were tested on the water sampled from three karstic springs in Romania, followed by water chemistry and whole community 16S rRNA gene-based metabarcoding analysis; (3) Results: We found that the different types of applied membrane filters provide a varying recovery of diversities and abundances of both overall and pathogenic bacteria; and (4) Conclusions: The result of the experiment with different filters shows which are the best for amplicon-based metabarcoding monitoring of karst springs.
ARTICLE | doi:10.20944/preprints202009.0205.v1
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: Franz-Bampa; BCS drugs; biomimetic membrane; Franz cell; passive drug transport
Online: 9 September 2020 (10:25:54 CEST)
A major parameter controlling the extent and rate of oral drug absorption is permeability through the lipid bilayer of intestinal epithelial cells. Here, a biomimetic artificial membrane permeability assay (Franz-Bampa) was validated using Franz cells apparatus. Both high and low permeability drugs (metoprolol and mannitol, respectively) were used as external standards. Biomimetic properties of Franz-Bampa were also characterized by electron paramagnetic resonance spectroscopy (EPR). Moreover, the permeation profile for the 14 BCS class I-IV drugs cited in the FDA guidance (including other drugs as acyclovir, cimetidine, diclofenac, ibuprofen, piroxicam, and trimethoprim) were measured across Franz-Bampa. Apparent permeability (Papp) was compared to literature fraction dose absorbed in humans (Fa%). Papp in Caco-2 cells and Corti artificial membrane were likewise compared to Fa% to assess Franz-Bampa performance. Mannitol and metoprolol Papp values across Franz-Bampa were lower (3.20 x 10-7 and 1.61 x 10-5 cm/s, respectively) than those obtained across non-impregnated membrane (2.27 x 10-5 and 2.55 x 10-5 cm/s, respectively), confirming lipidic barrier resistivity. Performance of the Franz cell permeation apparatus using an artificial membrane showed similar log linear correlation (R2 = 0.664) with Fa%, as seen for Papp in Caco-2 cells (R2 = 0.805). Data support the validation of the Franz-Bampa method for use during drug discovery process.
ARTICLE | doi:10.20944/preprints202004.0512.v6
Subject: Keywords: SARS-CoV-2; COVID-19; Coronavirus; Virus; sugar transporter; SemiSWEET; Membrane glycoprotein, Pandemic
Online: 19 October 2020 (10:48:05 CEST)
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the disease COVID-19 that has decimated the health and economy of our planet. The virus causes the disease not only in people but also in companion and wild animals. People with diabetes are at risk of the disease. As yet we do not know why the virus is highly successful in causing the pandemic within 3 months of its first report. The structural proteins of SARS include, membrane glycoprotein (M), envelope protein (E), nucleocapsid protein (N) and the spike protein (S). The structure and function of the most abundant structural protein of SARS-CoV-2, the membrane (M) glycoprotein is not fully understood. Using in silico analyses we determined the structure and potential function of the M protein. The M protein of SARS-CoV-2 is 98.6% similar to the M protein of bat SARS-CoV, maintains 98.2% homology with pangolin SARS-CoV, and has 90% homology with M protein of SARS-CoV; whereas, the similarity was only 38% with the M protein of MERS-CoV. In silico analyses showed that the M protein of SARS-CoV-2 has a triple helix bundle, form a single 3-transmembrane domain (TM), and are homologous to the prokaryotic sugar transport protein semiSWEET. SemiSWEETs are related to the PQ-loop family that function as cargo receptors in vesicle transport, mediates movement of basic amino acids across lysosomal membranes, and is also involved in phospholipase flippase function. The advantage and role of the M protein having a sugar transport-like structure is not clearly understood. The M protein of SARS-CoV-2 interacts with S, E and N protein. The S protein of the virus is glycosylated. It could be hypothesized that the sugar transporter-like structure of the M protein influences glycosylation of the S protein. Endocytosis is critical for the internalization and maturation of RNA viruses, including SARS-CoV-2. Sucrose is involved in endosome and lysosome maturation and may also induce autophagy, pathways that help in the entry of the virus. Overall, it could be hypothesized that the semiSWEET sugar transporter-like structure of the M protein may be involved in multiple functions that may aid in the rapid proliferation, replication and immune evasion of the SARS-CoV-2 virus. Biological experiments would validate the presence and function of the semiSWEET sugar transporter.
ARTICLE | doi:10.20944/preprints201912.0293.v2
Subject: Biology, Other Keywords: radiotherapy; glioblastoma; membrane Hsp70; dose- and time-kinetics; NK cell-based therapy
Online: 27 March 2020 (02:12:22 CET)
The major stress-inducible Hsp70 (HSPA1A) is overexpressed in the cytosol of many highly aggressive tumor cells including glioblastoma multiforme and presented on their plasma membrane. Depending on its intracellular or membrane localization, Hsp70 either promotes tumor growth or serves as a target for NK cells. The kinetics of the membrane Hsp70 (mHsp70) density on human glioma cells (U87) was studied after different irradiation doses to define the optimal therapeutic window for Hsp70-targeting NK cells. To maintain the cells in the exponential growth phase during a cultivation period of 7 days different initial cell counts were seeded. Although cytosolic Hsp70 levels remained unchanged on days 4 and 7 after a sublethal irradiation with 2 Gy, 4 Gy and 6 Gy, a dose of 2 Gy resulted in an upregulated mHsp70 density in U87 cells which peaks on day 4 and starts to decline on day 7. Higher radiation doses (4 Gy, 6 Gy) resulted in an earlier and more rapid onset of the mHsp70 expression on days 2 and 1, respectively, followed by a decline on day 5. Membrane Hsp70 levels are higher in G2/M than in G1, however, an irradiation-induced cell cycle arrest on days 4 and 7, was not associated with an increase in the mHsp70 density. Extracellular Hsp70 concentrations increased significantly compared to sham (0 Gy) irradiated cells on days 4 and 7 but not on day 1. Functionally, elevated mHsp70 densities were associated with a significantly better lysis by Hsp70-targeting NK cells. In summary, the kinetics of changes in the mHsp70 density upon irradiation on tumor cells is time- and dose-dependent.
ARTICLE | doi:10.20944/preprints201812.0003.v1
Subject: Life Sciences, Immunology Keywords: NK cell clones; IL-2; K562-mbIL21; membrane-bound IL-21
Online: 2 December 2018 (10:33:00 CET)
A pattern of NK cell heterogeneity in each individual determines proliferative and functional responses of NK cells to activating stimuli. Obtaining the progeny of a single cell by cloning original population is one of the ways to study the NK cell heterogeneity. In this work, we used single cell sorting into a plate and stimulation by IL-2 and gene-modified K562 feeder cells expressing membrane-bound IL-21 (K562-mbIL21) that led to generation of phenotypically confirmed and functionally active NK cell clones. We applied two models of clone cultivation, which differently affected their phenotype, lifespan and functional activity. The first model, which included weekly restimulation of clones with K562-mbIL21 and IL-2, resulted in the generation of relatively short-lived (5-7 weeks) clones of highly activated NK cells. HLA-DR expression in the expanded NK cells correlated strongly with IFN-γ production. The second model, in which NK cells were restimulated mainly with IL-2 alone, produced long-lived clones (8-14 weeks) that expanded up to 107 cells with lower ability to produce IFN-γ. Our method is applicable for studying variability in phenotype, proliferative and functional activity of the certain NK cell progeny in response to the stimulation, which may help in selecting NK cells best suited for clinical use.