CONCEPT PAPER | doi:10.20944/preprints202003.0401.v1
Subject: Life Sciences, Biophysics Keywords: SNAP25; linker; protein lipid interaction; acceptor complex; exocytosis; fusion
Online: 27 March 2020 (02:56:59 CET)
A recent paper demonstrates the importance of the linker region joining the two SNARE motifs of the neuronal t-SNARE SNAP25 for maintaining rates of secretion with roles for distinct segments in speeding fusion pore expansion (Shaaban et al., 2019, Elife. 8). Remarkably, lipid perturbing agents rescue a palmitoylation-deficient phenotype that includes slow fusion pore expansion, suggesting that protein-protein interactions have a role not only in bringing together the granule or vesicle membrane with the plasma membrane but also in orchestrating protein-lipid interactions leading to the fusion reaction. Furthermore, biochemical investigations demonstrate the importance of the C-terminal domain of the linker in the formation of the plasma membrane t-SNARE acceptor complex for synaptobrevin2 (Jiang, et al., 2019, FASEB J. 33:7985-7994;Shaaban et al., 2019, Elife. 8). This insight, together with biophysical and optical studies from other laboratories (Wang, et al., 2008, Molecular Biology of the Cell. 19:3944-3955; Zhao, et al., 2013, Proc Natl Acad Sci U S A. 110:14249-14254) suggests that the plasma membrane SNARE acceptor complex between SNAP25 and syntaxin and the resulting trans SNARE complex with the v-SNARE synaptobrevin form just milliseconds before fusion.
ARTICLE | doi:10.20944/preprints201611.0030.v1
Subject: Chemistry, Physical Chemistry Keywords: neutral organic radical; perchlorotriphenylmethyl radical; tetrathiafulvalene; donor-acceptor
Online: 4 November 2016 (14:19:09 CET)
During the last years there has been a high interest in the development of new purely-organic single-component conductors. Very recently, we have reported a new neutral radical conductor based on the perchlorotriphenylmethyl (PTM) radical moiety linked to a monopyrrolo-tetrathiafulvalene (MPTTF) unit by a -conjugated bridge (1). Interestingly, this system behaves as a semiconductor with high conductivity and small energy gap under high pressure. With the aim of developing a new material with improved conducting properties, we have designed and synthesized the radical dyad 2 which was functionalized with an ethylenedithio (EDT) group in order to improve the intermolecular interactions of the TTF subunits. The physical properties of the new radical dyad 2 were studied in detail in solution to further analyze its electronic structure as well as its potential use as radical conductor in the solid state.
REVIEW | doi:10.20944/preprints202204.0162.v1
Subject: Chemistry, Physical Chemistry Keywords: Electron transfer; artificial photosynthesis; supramolecular assemblies; Donor-bridge-acceptor system; transient absorption spectroscopy
Online: 18 April 2022 (09:29:09 CEST)
In this review, photoinduced electron transfer processes in specifically designed assembled ar-chitectures have been investigated on the basis of recent results reported from our laboratories. A convenient and useful way to study these kinds of systems has been described in order to under-stand the rules that drive to a light induced charge separation and its subsequent decay to the ground state, also with the aim of offering a tutorial for young researchers. Assembled systems of covalent or supramolecular nature have been presented and some functional multicomponent systems for the conversion of light energy into chemical energy have been discussed.
ARTICLE | doi:10.20944/preprints202002.0453.v1
Subject: Chemistry, Medicinal Chemistry Keywords: Michael acceptor; safe covalent drugs; oxidative stress inducers; trans-cinnamaldehyde; curcumin; colorectal cancer
Online: 29 February 2020 (04:22:03 CET)
Curcumin and trans-cinnamaldehyde are acrolein-based Michael acceptor compounds that are commonly found in domestic condiments, and known to cause cancer cell death via redox mechanisms. Based on the structural features of these compounds we designed and synthesized several 2-cinnamamido-N-substituted-cinnamamide (bis-cinnamamide) compounds. One of the derivatives, (Z)-2-[(E)-cinnamamido]-3-phenyl-N-propylacrylamide 1512 showed a moderate antiproliferative potency (HCT-116 cell line inhibition of 32.0 µM), good selectivity profile (no inhibition of normal cell lines), and proven cellular activities leading to apoptosis. SAR studies led to more than 10-fold increase in activity. Our most promising compound, [(Z)-3-(1H-indol-3-yl)-N-propyl-2-[(E)-3-(thien-2-yl)propenamido)propenamide] 4112 killed colon cancer cells at IC50 = 0.89 µM (Caco-2), 2.85 µM (HCT-116) and 1.65 µM (HT-29), while exhibiting much weaker potency on C-166 and BHK normal cell lines (IC50 = 71 µM and 77.6 µM, respectively). Cellular studies towards identifying the compounds mechanism of cytotoxic activities revealed that apoptotic induction occurs in part as a result of oxidative stress. Importantly, the compounds showed inhibition of cancer stem cells that are critical for maintaining the potential for self-renewal and stemness. The results presented here show discovery of covalently-acting Michael addition compounds that potently kill cancer cells by a defined mechanism, with minimal effect on normal noncancerous cell.
ARTICLE | doi:10.20944/preprints202106.0306.v1
Subject: Chemistry, Analytical Chemistry Keywords: eutectic mixtures; hydrogen bond acceptor; hydrogen bond donor; design of experiments; Tauc plot; band gap energy
Online: 11 June 2021 (08:52:30 CEST)
Three ternary mixtures composed by choline chloride (ChCl), ethylene glycol (EG) and a second hydrogen bond donor (HBD) as ethanol (A), 2-propanol (B), and glycerol (C) were studied in terms of composition related to the band gap energy (BGE). A Design of Experiments (DoE) approach, and in particular a Simple Lattice three-components design, was employed for determining the variation of the BGE upon the composition of each system. UV-VIS analysis and subsequent Tauc plot methodology provided the data requested from the DoE and multivariate statistical analysis revealed a drop of the BGE in correspondence to specific binary compositions for systems A and B. In particular, a BGE of 3.85 eV was registered for the mixtures ChCl/EtOH (1:1), and ChCl/2-propanol (1:1), which represents one of the lowest values ever observed for these systems.
ARTICLE | doi:10.20944/preprints201709.0141.v1
Subject: Chemistry, General & Theoretical Chemistry Keywords: purine and рyrimidine bases; donor/acceptor properties; quantum-chemical calculations; frontier levels; middle energy gap; parameter φ
Online: 28 September 2017 (03:13:48 CEST)
We have studied the relative positions of the frontier levels determine the main electronic properties and reaction ability, there is important necessity to compare the MO of the purine and рyrimidine bases: adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). The donor and acceptor properties are the fundamental characteristic of the conjugated molecules and can be quantitatively estimated by relative positions of the frontier molecular orbitals. The MO’s energies can be estimated experimentally or quantum-chemically. Analysis of the relative position of the frontier levels (calibrated by the energy gap) enables the investigation of the donor/acceptor properties of the RNA/DNA bases more detailed. The index φ0 is proposed for the quantitative quantum-chemical estimation of the donor ability of the conjugated molecules: it points on the shifting of the energy gap relative to the reference electron balanced system. The RNA/DNA bases divided strictly by two groups: predominantly donors (φ0 > 0.5) and predominantly acceptors (φ0 > 0.5). Each representative base of the first group forms the stable base pair the representative base of the second group the difference of indices Δφ0 should be optimal to enables the DNA replication.