E. S. Chukhrai

Total external reflection X-ray fluorescence analysis of protein-metal ion interactions in biological systems

This paper presents the results of an investigation into hemoglobin-based protein films that were formed on a liquid surface. X-ray standing wave measurements were performed at the ID 10 beamline of the European Synchrotron Radiation Facility (ESRF) and at the Langmuir station of the Kurchatov Synchrotron Radiation Source. It was found that the ability of the protein to bind metal ions is substantially increased due to the conformational rearrangements of protein macromolecules caused by various damaging effects. The elemental composition of protein preparations, which were isolated from children and adults with chronic metabolic diseases accompanied by endogenous intoxication, was analyzed. The results of the investigations offer evidence that an increase in the ligand-binding properties of the protein molecules, which was observed in model experiments using protein films, is a common trait and corresponds to in vivo processes accompanying metabolic disturbances in the body.

The Special Features of Protein Adsorption Isotherms on Silica Adsorbents

The adsorption isotherms of hemoglobin, peroxidase, and β-galactosidase on silochrome and mesoporous and biporous silicas were comparatively studied. Adsorption developed in two stages, including fast “reversible” protein adsorption (equilibrium was reached in t ≤ 1–2 h) and a “slow stage” of irreversible binding in t ≫ 24 h (multipoint adsorption). The corresponding equilibrium constants were determined. The mechanism of unlimited linear association of peroxidase in the adsorption layer on the surface of silochrome was established.

Long-Lasting Effects of Chemical Exposures in Mice

Genetically inbred strains of mice provide an excellent model for the study of normal variation in olfaction and for evaluating how sensitivity to odorants can be modulated by environmental exposures. Using two inbred strains, one quite sensitive to androstenone (CBA/J) and the other (NZB/B1NJ) insensitive to the odorant, we have been exploring both genetic and environmental contributions to variation in olfaction. Herein we present behavioral and biochemical correlates of the effects of exposures to androstenone during different times in the development of young mice and we explore some long-lasting effects of such exposures. Although exposures to androstenone per se induce sensitization to the compound, exposures during days 14-28 of age appear to maximize such effects. Furthermore, the effects of early exposures on behavioral sensitivity were noted in mice that were over 8 months old (comparable to a human beyond mid-life). Biochemical changes in the sensory epithelia also were noted: Here too, the effects were long-lasting. These results suggest that, although genetics may limit or set boundaries upon emergent potential, early exposures to odorants may have direct, long-lasting impact upon the sensory apparatus and its central nervous system (CNS) connections, and hence upon the behavior of individuals.

DISTINCT EFFECT OF XENOBIOTICS ON THE METAL-BINDING PROPERTIES OF PROTEIN MOLECULES

The X-ray standing-wave method was applied to study the elemental composition and molecular organization of ordered protein films of alkaline phosphatase exposed to different xenobiotics (drug compounds, lead). Binding of metal ions from triply distilled water to protein molecules has been experimentally observed. Definite differences in the arrangement of impurity metal ions in the films have been established. The considerable enhancement of protein-metal interactions is attributed to partial rearrangement of the protein native structure, induced by xenobiotics.

Adsorption characteristics of lysozyme on silochrome at different pH values

It is established that the adsorption of lysozyme on silochrome proceeds by a two-stage scheme that includes equilibrium adsorption and irreversible multipoint binding, complicated by the association of surface protein. It is shown that, a substantial change in the mechanism of adsorption occurs in dependence on pH. The density of the monolayer increases with increasing pH in the range of 6–10. The rate constants of adsorption and sites occupied by a molecule of protein at different pH values are calculated.

The influence of complexing pharmaceutical compositions on alkaline phosphatase

It is established that the pharmaceutical compositions xydiphon, medifon, succimer, and EDTA, which are used as complexing agents for accelerating the excretion of heavy metals from human organism, at certain concentrations inhibit enzyme alkaline phosphatase (AP). It is concluded that xydiphon and EDTA have a noticeable effect on AP activity at concentrations over 0.01 mM; medifon and succimer, at concentrations of over 0.3–0.5 mM. The enzyme’s inhibition constants and type of inhibition are determined. Xydiphon is found to manifest the highest affinity to AP (KI = 0.35 mM). It is shown by kinetic analysis that dissociative chemoinactivation of the enzyme takes place under the action of complexing agents. The corresponding kinetic parameters are calculated.