Random sequences with power-law correlations exhibit proteinlike behavior

We use a replica approach to investigate the thermodynamic properties of the random heteropolymers with persistent power-law correlations in monomer sequence. We show that this type of sequences possess proteinlike properties. In particular, we show that they can fold into stable unique three-dimensional structure (the "native" structure, in protein terminology) through two different types of pathways. One is a fast folding pathway and leads directly to the native structure. Another one, a more slower pathway, passes through the microphase separated (MPS) state and includes a number of intermediate glassy states. The scale and the magnitude of the MPS are calculated. The frozen state can be reached only by sequences with weak long-range correlations. The critical value for the correlation exponent is found, above which (strong correlations) freezing is impossible.     

Structure,mechanical, and tribological characteristics of polyurethane modified with nanodiamonds

The effect of modifying additives based on detonation nanodiamonds on the tribological characteristics of polyurethane rubber is studied. Introduction of modifying additives based on detonation nanodiamonds (0.5 wt %) leads to a marked improvement in the antifriction and wear-resistance characteristics under conditions of boundary sliding friction for steel and for lubrication with water. The attained tribological characteristics (total energy loss for friction, weight loss of polymer during tribological contact, maximum admissible working pressure) are well (∼300%) above the corresponding characteristics of foreign analogs. Changes in the tribological characteristics of the formed nanocomposite material are observed, but the elastic and strength characteristics remain unchanged.     

Synthesis and Electrochemical Properties of 2-(4-R 1 -Phenyl)-6-(4-R 2 -phenyl)-4-phenyl-3,4-dihydro1,2,4,5-tetrazin-1(2 H )-yls

A new methodology for creating electroactive components for organic batteries, based on the construction of a molecular platform including stable 3,4-dihydro-1,2,4,5-tetrazin-1(2H)-yl radicals was described. A series of 2-(4-R1-phenyl)-6-(4-R2-phenyl)-4-phenyl-3,4-dihydro-1,2,4,5-tetrazin-1(2H)-yls with substituents of various nature was obtained. It was shown that the substituents R1 in the aromatic ring at position 2 of the tetrazinyl fragment influence the value of the oxidation potential in the radical, but do not influence the value of the reduction potentials, while the substituent R2 of the aromatic ring at position 6 influence the values of the reduction potentials and practically do not influence oxidation potential values. Based on the obtained electrochemical data, a correlation structure–potential value was revealed for the cathodic and anodic process, with the help of which triarylsubstituted 3,4-dihydro-1,2,4,5-tetrazin-1(2H)-yl radicals with high values of the electrochemical gap were obtained.     

Effect of the hyaluronidase microe nvironment on the enzyme structure–function relationship and computational study of the <Emphasis Type="Italic">in silico</Emphasis> molecular docking of chondroitin sulfate and heparin short fragments to hyaluronidase

The review addresses the biochemical interactions of hyaluronidases with components of the natural microenvironment. The effect of subtle structural differences between ligands on the enzyme structure–function relationship regulation is noted. Docking of chondroitin sulfate (CS) trimers (hexasaccharides) and heparin tetramers (octasaccharides) to the 3D model of the bovine testicular hyaluronidase (BTH) was performed by computational chemistry methods in order to elucidate the mechanism of regulation of the enzyme functioning in the body (using virtual screening, molecular dynamics, and calculation of surface electrostatic potential of protein complexes). Several binding sites for glycosaminoglycan (GAG) ligands were found to occur on the hyaluronidase surface. They are identical for CS trimers and heparin tetramers. The calculations showed the possibility of both reversible and irreversible conformational changes of the 3D structure of BTH, depending on the arrangement of negatively charged ligands on its globule. When the changes are irreversible, Glu-149 and Asp-147, which are key amino acid residues for the catalytic activity of BTH, can migrate from the vicinity of the native enzyme active site to the periphery of the protein molecule, thus inducing enzyme inactivation. The interaction of the GAG ligands with the BTH active site is mainly caused by electrostatic forces. Four or five binding sites of the chondroitin sulfate trimer proved to be critical for stabilization of the enzyme structure. Their occupation was sufficient for preventing irreversible deformation of the BTH molecule upon the insertion of the heparin ligand into the active site cavity. Protein stabilization is accompanied by the formation of a particular form of the surface electrostatic potential.     

Six-Nuclear Complexes of Platinum(II) and Palladium(II) with Mercamine and β-Mercaptoethanol

The platinum(II) and palladium(II) complexes [Pt₆(SCH₂CH₂NH₂)₈]Cl₄ and [Pd₆(SCH₂CH₂OH)₈ Cl₄· 5H₂O with mercamine and β-mercaptoethanol, respectively, were synthesized. It was found on the basis of the comparison of IR and X-ray electron spectra of the ligands and complexes, and also of the data of X-ray diffraction analysis that the bidentate coordination of ligands through sulfur and nitrogen atoms is realized in the platinum(II) complex. In the palladium(II) complex β-mercaptoethanol is coordinated in a mixed-mode type. In both complexes sulfur atoms of the ligands occupy a bridging position.     

Density functional theory for investigation of optical and spectroscopic properties of zinc-quinonoid complexes as semiconductor materials

Structural Chemistry - Three Zn(II) complexes of a new organic compound [(E)-4-methyl-N1-((E)-4-methyl-6-(p-tolylimino) cyclohex-3-en-1-ylidene)-N2-(p-tolyl) benzene-1, 2-diamine] (HMBD) were...     

The chlorination kinetics of zirconium dioxide mixed with carbon black

In this research, the effects of chlorine gas at different chlorine partial pressures and carbon concentrations on the carbochlorination of zirconia were studied. It was found that in briquettes containing 18.7 %wt carbon, in a chlorine partial pressure range of 0.25–0.75 atm and for a reacted fraction of less than 0.7, the chemical reaction model was dominant for the carbochlorination process of zirconia. The order of reaction into chlorine gas (n) in this situation was 0.57. Moreover, the best weight ratio of carbon to zirconia was 40/60. In this case, the activation energy of the reaction was 209.9 kJ mol^?1 in a temperature range of 1023–1223 K, and the dominant model was the chemical reaction model.