Viscoelastic characteristics of protein solutions and the micromechanics of their motion in porous carriers

The interactions of model proteins with porous matrices in biosensors are considered. The viscoelastic properties of casein and albumin were assessed by a dynamic method of a piezoquartz resonator by applying thin layers of the studied solutions to a piezocrystal. The experimental data on the viscoelastic characteristics of protein solutions of various concentrations were compared with the characteristics of their tangential motion in the porous carriers of cellulose nitrate. It was demonstrated that the parameters of dynamic viscosity correlated with the motion time of the protein solutions in the porous polymeric carrier.     

Oak wood hemicelluloses extracted with aqueous-alcoholic media

Hemicellulose fractions were isolated from oak wood ethanol extracts (40–90%). To determine the composition of these fractions, they were hydrolyzed and the hydrolysis products in the form of trimethylsilyl derivatives were analyzed by GLC/MS. Depending on the content of the ethanol, hemicelluloses of a different composition were extracted from wood. In alcohols that were kept in oak wood, intended for manufacturing brandy and whisky, the content of the hemicelluloses increased depending on the duration of storage. It is assumed that this makes drinks more full-bodied and makes them softer.     

Study of Development of Function of Kidneys and Their Regulation on the Background of Pathological Process

By the example of reabsorption of sodium ions in kidney, it is shown that this process, alongside with establishment of the system of osmotic concentration, plays the key role in evolution of renal function. There is shown a similarity of tendencies of changes of the total sodium ion reabsorption in children’s kidney in the process of development and in a series of representatives of various vertebrate classes. An opposite tendency is revealed during the kidney dysfunction produced by chronic renal failure. At all stages of postnatal ontogenesis in healthy children and in adults, kidney maintains the same parameters of the blood serum ion composition and osmolality. A new approach to study evolution of functions is proposed, which is based on a combination of two L.A. Orbeli’s methods—ontogenetic and clinical, by the example of study of renal function and its regulation during development of a pathological process on the background of formation of function in postnatal ontogenesis. When using such approach in children with nocturnal enuresis, significance of autacoids in regulation of urine formation is established. In the case of acute pneumonia in children, a possibility of extrapituitary production of vasopressin-like substances in lungs is shown. In norm, in postnatal ontogenesis of healthy children, in regulation of renal functions and of diuresis system, effects of efferent nerves and hormones (vasopressin) dominate, while significance of autacoids is minimal. But at a dysfunction produced by a pathological process, a change of ratio of activities of these regulatory systems is revealed. The obtained data indicate importance of the clinical and experimental methods proposed by L.A. Orbeli in analysis of evolution of renal functions and study of the nature of regulations. A combination of several methods of evolutionary physiology in one study allows revealing new mechanisms underlying regulation of function and promotes formation of concepts about regularities of evolution of functions.__________Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 3, 2005, pp. 277–284.Original Russian Text Copyright © 2005 by Kuznetsova, Natochin.     

Regulation of microRNA activity in stress

Stressors substantially affect the physiology of cells. Depending on the severity and duration of stress exposure, cells either strive to maintain homeostasis or adapt by adjusting their gene expression patterns. One of the mechanisms to change gene expression is regulating the microRNA (miRNA) levels and activities of microRNA–protein complexes. A fine tuning of the interaction of miRNAs with their mRNA targets determines the specificity of protein synthesis and the quantitative composition of the protein pool in stress. The review considers the mechanisms that regulate miRNA biogenesis, miRNA-mediated mRNA repression, and activity of miRNA–protein complexes in animal cells exposed to various stress factors.     

Simulation of protein misfolding using a lattice model

The structure of the tightly bound complex of the globular myosin head with F-actin is the key to understanding important details of the mechanism of how the actin-myosin motor functions. The current notion on this complex is based on the docking of known atomic structures of constituent proteins into low-resolution electron-density maps. The atomic structure of the complex was refined by the molecular mechanics method, which consists in minimizing the energy of molecular interaction and which makes it possible to optimize not only the relative position of protein backbones as rigid bodies, but also the position of side chains on the protein interface. The structure calculated using ICM-Pro software, on the one hand, is close to the model obtained using electron microscopy; on the other hand, it ensures the best calculated interaction energy and accounts for the results of mutagenesis experiments. On the basis of the structure obtained, we can suggest the molecular mechanisms underlying the actin-activated release of ATP hydrolysis products from myosin and the decrease in the affinity of myosin for actin upon binding of nucleotides.