[Physico-chemical and biological properties of a new plasma substitute based on hydroxyethylated starch]. / Fiziko-khimicheskie i biologicheskie svoistva novogo plazmozamenitelia na osnove oksiétilirovannogo krakhmala.

Samples of hydroxyethylstarch of M 100-160 kDa, Mn 50-60 kDa and substitution degree 0.6-0.7 were prepared and characterized. Hydroxyethylstarch was shown to be susceptible to cleavage by amylolytic enzymes. All samples of hydroxyethylstarch at 2-4% concentration were compatible with perfluorohydrocarbon emulsion "Perftoran" and exhibited high haemodynamic efficiency. The 6 and 10% solutions of hydroxyethylstarch in 0.9% aqueous sodium chloride normalized haemodynamics in massive blood losses. Hydroxyethylstarch was completely removed from blood-stream. The preparations were shown to be nontoxic.

[Kinetics and mechanism of nucleophilic effect on the oxidation of o-dianisidine catalyzed by horseradish peroxidase]. / Kinetika i mekhanizm deistviia nukleofilov na reaktsiiu okisleniia o-dianizidina, kataliziruemuiu peroksidazoi nz khrena.

The effects of benzimidazole and 4-nitroimidazole on the reaction of o-dianisidine peroxidase oxidation within the pH range of 3.7--9.0 were studied. Both substituted imidazoles activate the reaction at less than 0.6. In the presence of 4-nitroimidazole the activation is non-competitive, whereas in the presence of benzimidazole it is of a mixed type, which is close to the non-competitive one. The kinetic parameters (kAcat, alpha, KA) for the reaction activated by both imidazoles were determined. It was assumed that the activators interact with the protein group (pK approximately to 6.5), which limits the enzyme activity. This results in the increase of pKapp of the protein group in question, resulting in the appearance of the maximal peroxidase activity in the alkaline region of pH. It was shown that the intermolecular interactions involved in the peroxidase-induced oxidative catalysis are largely due to electrostatic rather than to hydrophobic factors.

[Effect of N-alkylimidazoles on oxidation of o-dianizidine catalyzed by horseradish peroxidase]. / Vliianie N-alkilimidazolov na okislenie o-dianizidina, kataliziruemoe peroksidazoi iz khrena.

Effect of a number of N-alkylimidazoles (from N-methyl to N-octylimidazole) on peroxidase oxidation of o-dianizidine at pH 8.0 is studied. Alkylimidazoles studied are found to activate the reaction under given conditions, the activation type being non-competitive KA and (alpha) values are similar for all the activators, which suggests a similar mechanism of their action. Similar KA values suppose an insignificant role of hydrophobic interactions in the binding of N-alkylimidazoles with the enzyme.