ARTICLE | doi:10.20944/preprints202104.0675.v1
Subject: Materials Science, Biomaterials Keywords: Carbon nanotubes; Functionalization; Sulfonated Poly-Ether-Ether-Ketone; FTIR
Online: 26 April 2021 (13:29:14 CEST)
.Functionalization of multi-walled carbon nanotubes (MWNTs) surface with sulfonated poly(ether ether ketone) SPEEK chains using hexane diamine (HAD) as the interlinking molecule was investigated. MWNTs were first oxidized by nitric acid to generate carboxyl groups on their surface. Grafting of SPEEK chains on the MWNTs surface was achieved using hexane diamine as a cross-linking molecule. The attachment took place after the reaction of amine groups with carboxyl groups of oxidized MWNTs and sulfonate groups of SPEEK as confirmed by infrared (FTIR) analysis. Scanning electron microscopy (SEM) showed that MWNTs were packed into a dense and compact structure. Transmission electron microscopy (TEM) showed that the nanotubes were wrapped by polymer chains and arranged in a bundle like structure. These observations reveal that some of MWNTs were interconnected by SPEEK chains.
REVIEW | doi:10.20944/preprints202009.0133.v1
Subject: Life Sciences, Other Keywords: Cognition; nutrition; metabolism; neurodegeneration; ketone bodies; glycaemia; nutrition therapy
Online: 5 September 2020 (08:29:52 CEST)
Although diet interventions are mostly related to metabolic disorders, nowadays they are used in wide variety of pathologies. From diabetes and obesity to cardiovascular diseases, through cancer or neurological disorders and stroke, nutritional recommendations applied to almost all diseases. Among those disorders, metabolic disturbances and brain function and/or diseases have recently been shown to be linked. Indeed, numerous neurological functions are often associated with perturbations of whole-body energy homeostasis. In this regard, specific diets are used in various neurological conditions such as epilepsy, stroke, or seizure recovery. In addition, Alzheimer’s disease or Autism Spectrum Disorders are also considered as putatively improved by diet intervention. Glycemic index diets are a novel developed indicator expected to anticipate the changes in blood glucose induced by specific foods, and how they can affect various physiological function. Several results provide indications of efficiency of low glycemic index diets in weight management, insulin sensitivity, but also cognitive function, epilepsy treatment, stroke, or neurodegenerative diseases. Overall, studies involving glycemic index could provide new insight in the relationship between energy homeostasis regulation and brain function or related disorders. Therefore, in this review we will summarize main evidences on glycemic index involvement in brain mechanisms of energy homeostasis regulation.
ARTICLE | doi:10.20944/preprints202012.0653.v1
Subject: Chemistry, Analytical Chemistry Keywords: ketone body ester; lipase; kinetic resolution; asymmetric synthesis; configuration inversion.
Online: 25 December 2020 (10:50:32 CET)
The oral administration of (R)-3-hydroxybutyl-(R)-3-hydroxybutyrate, allows inducing a beneficial level of blood ketone bodies without the adverse effects due to the adhesion to a ketogenic diet. Several studies documented the therapeutic effectiveness of the (R)-3-hydroxybutyl (R)-3-hydroxybutyrate in treating neurodegenerative diseases as well as its boosting activity of athletic and cognitive performances during prolonged physical exercises. Further studies considering this ketone body ester for therapy of other pathologies are also underway. In the present work, we describe the synthesis of (R)-3-hydroxybutyl-(R)-3-hydroxybutyrate through the enantioselective transesterification of racemic ethyl 3-hydroxybutyrate with (R)-1,3-butanediol catalyzed by immobilized Candida antarctica lipase B (CAL-B). The enantiopure (R)-1,3-butanediol was in turn obtained from the kinetic resolution of the racemate by CAL-B catalyzed acetylation with vinyl acetate. The economy of the synthetic procedure has been improved by recycling the unreacted (S) enantiomers of the ethyl 3-hydroxybutyrate and 1,3-buatnediol after stereochemical inversion achieved by tosylation and SN2 with ammonium acetate. The overall procedure allows to incorporate up to 70% of the starting racemic reagents into the final product.
ARTICLE | doi:10.20944/preprints202009.0438.v1
Subject: Materials Science, Other Keywords: poly-ether-ether ketone; graphene oxide (GO); MoS2; tribological behaviours; mechanism
Online: 18 September 2020 (12:11:15 CEST)
Poly-ether-ether ketone (PEEK) is a great potential thermoplastic in industry and medical treatment and health. In this work, the PEEK/GO and PEEK/MoS2 composites were prepared by a novel hot isostatic pressing method. The addition of GO alters the tribological behaviours mechanism, fatigue wear mechanism is predominant to PEEK/GO composites. However, the combination of abrasive and adhesive wear mechanisms is observed for PEEK/MoS2 composites and PEEK. The reason is the hardness and tensile strength of composites are increased with the appropriate addition of GO. The response time to stable friction state of PEEK/GO and PEEK/MoS2 composites reduces in compared with PEEK, which conduce to shorten running-in time, reduce energy consumption and improve the tribological performances of composites. The addition of GO and MoS2 can effectively decrease the friction coefficient and wear rate, and the optimal content of GO and MoS2 was 0.7 wt.% and 15 wt.%, respectively. The results indicate that PEEK/GO and PEEK/MoS2 are impressive composites that possess super tribological properties.
ARTICLE | doi:10.20944/preprints202012.0711.v1
Subject: Chemistry, Analytical Chemistry Keywords: AHTN; HHCB; musk ketone; personal care product; sewage treatment plant; synthetic musk fragrance.
Online: 28 December 2020 (21:55:03 CET)
Levels of synthetic musk fragrances (SMFs) and various personal care products (PCPs) were measured in the Han River and its tributaries in Seoul, Korea. The most abundant SMF in all river and PCP samples was 4,6,6,7,8,8-hexamethyl-1,3,4,7-tetrahydrocyclopenta[g]isochromene (HHCB), followed by 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone (AHTN), musk ketone (MK), and 1,1,2,3,3-pentamethyl-2,5,6,7-tetrahydroinden-4-one (DPMI). There was a significant correlation between the SMF concentration in the PCPs and the Han River samples. Moving from upstream to downstream in the Han River, the median SMF concentration was 6.756, 2.945, 0.304, and 0.141 μg/L in the sewage treatment plant (STP) influent, effluent, tributaries, and mainstream, respectively, implying that effective SMF removal was achieved during the sewage treatment process, followed by dilution in the receiving water. Four STPs using advanced biological treatment processes had removal efficiencies of 55.8%, 50.6%, 43.3% for HHCB, AHTN, and MK, respectively. The highest SMF concentrations in the tributaries were observed at locations close to the STPs. Our study confirmed that the main source of SMFs in the receiving water were sewage effluent containing untreated SMFs, which are largely originated from household PCPs, especially hair care products (e.g., shampoo) and perfumes.
ARTICLE | doi:10.20944/preprints202008.0600.v1
Subject: Chemistry, Organic Chemistry Keywords: lipase; biocatalysis; Wieland-Miescher ketone; biocatalyst screening; amylase; peptidase; enantiomeric excess; Robinson Annulation
Online: 27 August 2020 (08:37:44 CEST)
Lipases, a versatile class of biocatalysts, have been shown to function in non-aqueous media/organic solvents and to possess promiscuous catalytic activity for a wide range of organic transformations. In this study, we explore the biocatalytic properties of a library of commercially available lipases by screening them for catalysis of a one-pot synthesis of Wieland-Miescher Ketone, an important intermediate in the synthesis of biologically active compounds such as steroids and terpenoids, from methyl vinyl ketone and 2-methyl-1,3-cyclohexanedione. As a direct outgrowth of this screen, we have created an optimized procedure for Wieland-Miescher Ketone (WMK) synthesis using crude lipase preparations, characterizing both reaction yield and enantiomeric excess. We have also identified principal components of the crude lipase mixture through proteomics and present evidence for a non-lipolytic origin of the observed catalysis. Finally, using the optimized conditions developed in this study, we propose a general absorbance-based screening methodology for assessing biocatalytic potential of crude enzyme preparations for synthesis of WMK.
ARTICLE | doi:10.20944/preprints202003.0194.v1
Subject: Materials Science, Surfaces, Coatings & Films Keywords: fiber-reinforced poly(ether-ether-ketone); surface modification; shear bond strength; surface analtsis
Online: 12 March 2020 (03:49:18 CET)
We investigated the effect of helium atmospheric-pressure plasma (PL) and deep-ultraviolet (UV) light treatments on the adhesive properties of fiber-reinforced poly(ether-ether-ketone)polymer (PEEK). PEEK disks reinforced with carbon (CPEEK) or glass (GPEEK) fibers were polished, modified with PL and UV for 60 s, and the surface energy was calculated by measuring the contact angles. The disk surfaces were analyzed by X-ray photoemission spectroscopy. Shear bond strength testing was performed using a universal testing machine, and the fracture surfaces were observed by electron probe microanalyzer. Data were analyzed with one and two-way ANOVA and Tukey’s post-hoc test (p < 0.05). The surface energies were increased by the modifications, which created OH functional groups on the surfaces. The bond strengths of CPEEK were increased by PL and those of GPEEK were increased by PL and UV, owing to chemical bonding at the interface.
ARTICLE | doi:10.20944/preprints202107.0462.v1
Subject: Chemistry, Analytical Chemistry Keywords: London dispersion; ketone complexes; density functional theory; hydrogen bonds; molecular recognition; vibrational spectroscopy; gas phase; benchmark
Online: 20 July 2021 (16:06:47 CEST)
Phenol is added to acetophenone (methyl phenyl ketone) and to six of its halogenated derivatives in a supersonic jet expansion to determine the hydrogen bonding preference of the cold and isolated 1:1 complexes by linear infrared spectroscopy. Halogenation is found to have a pronounced effect on the docking site in this intermolecular ketone balance experiment. The spectra unambiguously decide between competing variants of phenyl group stacking due to their differences in hydrogen bond strength. Structures where the phenyl group interaction strongly distorts the hydrogen bond are more difficult to quantify in the experiment. For unsubstituted acetophenone, phenol clearly prefers the methyl side despite a predicted sub-kJ/mol advantage which is nearly independent of zero point vibrational energy, turning this complex into a challenging benchmark system for electronic structure methods which include long range dispersion interactions in some way.
ARTICLE | doi:10.20944/preprints202009.0643.v1
Subject: Chemistry, Analytical Chemistry Keywords: dispersion; ketone-alcohol complexes; density functional theory; hydrogen bonds; molecular recognition; vibrational spectroscopy; gas phase; benchmark; pinacolone
Online: 26 September 2020 (14:57:33 CEST)
The influence of distant London dispersion forces on the docking preference of alcohols of different size between the two lone electron pairs of the carbonyl group in pinacolone is explored by infrared spectroscopy of the OH stretching fundamental in supersonic jet expansions of 1:1 solvate complexes. Experimentally, no pronounced tendency of the alcohol to switch from the methyl to the bulkier tert-butyl side with increasing size is found. In all cases, methyl docking dominates by at least a factor of two, whereas DFT-optimized structures suggest a very close balance for the larger alcohols, once corrected by CCSD(T) relative electronic energies. Together with inconsistencies when switching from a C4 to a C5 alcohol, this points at deficiencies of the investigated B3LYP and in particular TPSS functionals even after dispersion correction, which cannot be blamed on zero point energy effects. The search for density functionals which describe the harmonic frequency shift, the structural change and the energy difference between the docking isomers of larger alcohols to unsymmetric ketones in a satisfactory way is open.
REVIEW | doi:10.20944/preprints202102.0277.v1
Subject: Life Sciences, Biochemistry Keywords: energy metabolism; oligodendrocyte; oligodendrocyte progenitor cell; myelin; remyelination; multiple sclerosis; glucose; ketone bodies; lactate; N-acetyl aspartate; demyelination
Online: 11 February 2021 (10:57:28 CET)
Central nervous system (CNS) myelin has a crucial role in accelerating the propagation of action potentials and providing trophic support to the axons. Defective myelination and lack of myelin regeneration following demyelination can both lead to axonal pathology and neurodegeneration. Energy deficit has been evoked as an important contributor to various CNS disorders, including multiple sclerosis (MS). This suggests that dysregulation of energy homeostasis in oligodendroglia may be an important contributor to myelin dysfunction and lack of repair observed in the disease. This article will focus on energy metabolism pathways in oligodendroglial cells and highlight differences dependent on the maturation stage of the cell. In addition, it will emphasize that the use of alternative energy sources by oligodendroglia may be required to save glucose for functions that cannot be fulfilled by other metabolites, thus ensuring sufficient energy input for both myelin synthesis and trophic support to the axons. Finally, it will point out that neuropathological findings in a subtype of MS lesions likely reflect defective oligodendroglial energy homeostasis in the disease.