Serotonin Promotes Serum Albumin Interaction with the Monomeric Amyloid β Peptide

Prevention of amyloid β peptide (Aβ) deposition via facilitation of Aβ binding to its natural depot, human serum albumin (HSA), is a promising approach to preclude Alzheimer’s disease (AD) onset and progression. Previously, we demonstrated the ability of natural HSA ligands, fatty acids, to improve the affinity of this protein to monomeric Aβ by a factor of 3 (BBRC, 510(2), 248–253). Using plasmon resonance spectroscopy, we show here that another HSA ligand related to AD pathogenesis, serotonin (SRO), increases the affinity of the Aβ monomer to HSA by a factor of 7/17 for Aβ₄₀/Aβ₄₂, respectively. Meanwhile, the structurally homologous SRO precursor, tryptophan (TRP), does not affect HSA’s affinity to monomeric Aβ, despite slowdown of the association and dissociation processes. Crosslinking with glutaraldehyde and dynamic light scattering experiments reveal that, compared with the TRP-induced effects, SRO binding causes more marked changes in the quaternary structure of HSA. Furthermore, molecular docking reveals distinct structural differences between SRO/TRP complexes with HSA. The disintegration of the serotonergic system during AD pathogenesis may contribute to Aβ release from HSA in the central nervous system due to impairment of the SRO-mediated Aβ trapping by HSA.     

Fine Splitting of Electron States in Silicon Nanocrystal with a Hydrogen-like Shallow Donor

Electron structure of a silicon quantum dot doped with a shallow hydrogen-like donor has been calculated for the electron states above the optical gap. Within the framework of the envelope-function approach we have calculated the fine splitting of the ground sixfold degenerate electron state as a function of the donor position inside the quantum dot. Also, dependence of the wave functions and energies on the dot size was obtained.     

Synthesis and characterization of novel linear and crosslinked polyelectrolytes derived from the acetoacetic ester and acrylic acid

Summary Novel linear and crosslinked polyelectrolytes based on acetoacetic ester and acrylic acid were synthesized for the first time via Michael addition reaction followed by radical polymerization. The structure and properties of polyelectrolytes were characterized by FTIR, Raman and NMR spectroscopy, TGA, DSC, GPC, viscometry and potentiometric titration. Considerable influence of water content on the swelling rate of hydrogels was established. The swelling-deswelling properties of hydrogels were studied in dependence of pH, ionic strength and in water-organic solvent mixtures.     

PSIC: profile extraction from sequence alignments with position-specific counts of independent observations

Sequence weighting techniques are aimed at balancing redundantobserved information from subsets of similar sequences in multiplealignments. Traditional approaches apply the same weight toall positions of a given sequence, hence equal efficiency ofphylogenetic changes is assumed along the whole sequence. Thisrestrictive assumption is not required for the new method PSIC(position-specific independent counts) described in this paper.The number of independent observations (counts) of an aminoacid type at a given alignment position is calculated from theoverall similarity of the sequences that share the amino acidtype at this position with the help of statistical concepts.This approach allows the fast computation of position-specificsequence weights even for alignments containing hundreds ofsequences. The PSIC approach has been applied to profile extractionand to the fold family assignment of protein sequences withknown structures. Our method was shown to be very productivein finding distantly related sequences and more powerful thanHidden Markov Models or the profile methods in WiseTools andPSI-BLAST in many cases. The profile extraction routine is availableon the WWW (http://www.bork.embl-heidelberg.de/PSIC or http://www.imb.ac.ru/PSIC).     

Coherent anti-Stokes Raman scattering enhancement of thymine adsorbed on graphene oxide

Coherent anti-Stokes Raman scattering (CARS) of carbon nanostructures, namely, highly oriented pyrolytic graphite, graphene nanoplatelets, graphene oxide, and multiwall carbon nanotubes as well CARS spectra of thymine (Thy) molecules adsorbed on graphene oxide were studied. The spectra of the samples were compared with spontaneous Raman scattering (RS) spectra. The CARS spectra of Thy adsorbed on graphene oxide are characterized by shifts of the main bands in comparison with RS. The CARS spectra of the initial nanocarbons are definitely different: for all investigated materials, there is a redistribution of D- and G-mode intensities, significant shift of their frequencies (more than 20 cm^-1), and appearance of new modes about 1,400 and 1,500 cm^-1. The D band in CARS spectra is less changed than the G band; there is an absence of 2D-mode at 2,600 cm^-1 for graphene and appearance of intensive modes of the second order between 2,400 and 3,000 cm^-1. Multiphonon processes in graphene under many photon excitations seem to be responsible for the features of the CARS spectra. We found an enhancement of the CARS signal from thymine adsorbed on graphene oxide with maximum enhancement factor about 10⁵. The probable mechanism of CARS enhancement is discussed.     

Optical compensation for two stereoscopic distortions

Abstract— A stereoscopic display configuration for presenting stereoscopic images without keystone and depth‐plane‐curvature distortions is proposed. The main idea of the proposed configuration is to perform optical compensation for these distortions by presenting left and right perspective images at two intersecting screens. The possibility of such distortion elimination was proven by two independent ways: analytically and graphically.     

Enzymatic Synthesis of Ascorbyl Palmitate in Organic Solvents: Process Optimization and Kinetic Evaluation

This work is focused on the optimization of reaction parameters for the synthesis of ascorbyl palmitate catalyzed by Candida antarctica lipase in different organic solvents. The sequential strategy of experimental designs proved to be useful in maximizing the conditions for product conversion in tert-butanol system using Novozym 435 as catalyst. The optimum production were achieved at ascorbic acid to palmitic acid mole ratio of 1:9, stirring rate of 150 rpm, 70 °C, enzyme concentration of 5 wt.% at 17 h of reaction, resulting in an ascorbyl palmitate conversion of about 67%. Reaction kinetics for ascorbyl palmitate production showed that very satisfactory reaction conversions (∼56%) could be achieved in short reaction times (6 h). The kinetic empirical model proposed showed ability to satisfactory represents and predict the experimental data.     

High-strength ceramic based on zirconium dioxide: preparation and properties

Strength properties are considered for ZrO₂ hot-pressed ceramic materials stabilized with 4 – 6 wt.% Y₂O₃ in relation to original powder preparation method: solid phase synthesis, high-temperature salt thermolysis, combined hydroxide precipitation followed by freezing, drying and calcining, and the sol-gel method. Ceramic material with the highest strength in bending (up to 1350 MPa) are prepared from ZrO₂ – 5 wt.% Y₂O₃ powders, synthesized by coprecipitation of hydroxides followed by freezing.     

Isolated transmembrane helices arranged across a membrane: computational studies

A computational procedure for predicting the arrangement ofan isolated helical fragment across a membrane was developed.The procedure places the transmembrane helical segment intoa model triple-phase system `water–octanol–water';pulls the segment through the membrane, varying its `global'position as a rigid body; optimizes the intrahelical and solvationenergies in each global position by `local' coordinates (dihedralangles of side chains); and selects the lowest energy globalposition for the segment. The procedure was applied to 45 transmembranehelices from the photosynthetic reaction center from Rhodopseudomonasviridis, cytochrome c oxidase from Paracoccus denitrificansand bacteriorhodopsin. In two thirds of the helical fragmentsconsidered, the procedure has predicted the vertical shiftsof the fragments across the membrane with an accuracy of –0.15± 3.12 residues compared with the experimental data.The accuracy for the remaining 15 fragments was 2.17 ±3.07 residues, which is about half of a helix turn. The procedurepredicts the actual membrane boundaries of transmembrane helicalfragments with greater accuracy than existing statistical methods.At the same time, the procedure overestimates the tilt valuesfor the helical fragments.     

Synthesis of carbon-mineral composites and graphene

Abstract

С/Al₂O₃ and C/MgO carbon-mineral composites were synthesized by propane decomposition over Al₂O₃ at 600–650?°C and MgO carbonization in 1,3-butadiene at 600?°C. The synthesized carbon-mineral composites were studied by EPR, XRD and transmission electron microscopy. It was found that a mosaic structure of carbon clusters was formed on the internal surface of the oxides and gradually grew until it covered its whole surface. A method for synthesis of graphene materials by using MgO as a template followed by its dissolution in hydrochloric acid was suggested. A maximum was observed on the dependence of the graphene surface area on the carbon concentration in the composites. The highest specific surface area of the synthesized graphene about 1800–1900?m²/g was observed for the samples obtained from C-MgO composites containing 8–10?wt.% C.