[Study of temperature-dependent conformational changes in serum albumin using an adsorbed dye]. / Izuchenie zavisimykh ot temperatury konformatsionnykh prevrashchenii syvorotochnogo al'bumina pri pomoshchi adsorbirovannogo krasitelia.

4-N (p-sulfoaniline),5-methoxy,1,2-benzoquinon (1) is bound by hydrophobic regions of the native molecule of bovine serum albumin (BSA). In the temperature interval 0--65 degrees C the interaction characteristics such as energy, entropy and the average number of the binding sites on a BSA molecule were determined. Under experimental conditions BSA is found in at least in two equilibrium conformational states distinguished by quantity of hydrophobic regions capable of binding with 1. Below 17 degrees C no conformational changes of BSA was observed. With the increase of temperature from 17 to 47 degrees C the equilibrium is driven in the direction of protein form with the hydrophobic binding sites which are more available for the solvent. Heating above 47 degrees C produces "predenaturation" structural changes in the BSA molecule. Hydrophobic regions of the BSA have different thermal stability.

[Criteria selection for the preliminary evaluation of the efficacy of antihypoxic agents]. / K voprosu o vybore kriteriev predvaritel'noi otsenki éffektivnosti antigipoksantov

Mathematical description is suggested of oxygen consumption by mitochondria suspension in the presence of orto-benzoquinone derivatives. An analysis of the equations obtained, in vivo conditions taken into account, has shown that the efficiency of hydrogen consumption is mainly determined by the constant value of oxidation rate of quinone reduced form, poorely depends on the substrate concentration and activity of quinone-reducing enzymes. The constant value of oxidation rate may serve as a criterion of directed synthesis of antihypoxants.

[Mitochondrial menadione reductase: kinetics and mechanism of the action in situ]. / Mitokhondrial'naia menadionreduktaza kinetika i mekhanizm deistviia fermenta in situ

The formal mechanism of action of menadion reductase localized in the membrane of intact mitochondria in the rebox reaction of 4-N (p-sulfoanilin)-5-methoxy-1,2-benzoquinone with NADH as an electron donor has been studied by the stationary kinetics method. It has been shown that the mitochondrial menadion reductase incorporated into the membrane functions according to the "ping-pong" mechanism, similar to the functioning of the free enzyme. However, in this case an inhibitory effect of NADH has been noticed. A phenomenological equation, which is in a good accordance with the experimental data, has been suggested. Luminescence studies showed that a specific NADH-binding site located outside the active centre exists in the enzyme molecule. The model of the mechanism of the enzyme substrate inhibition in situ, responsible for a change in the conformation of the apoenzyme occurs upon NADH binding, is discussed.