[Quantum chemistry analysis of the mechanism of action of proteolytic enzymes. I. The state of the cleavable bond of substrates and intermediates].

Electronic parameters of amide and ester bonds in some compounds, modelling substrates of proteolytic enzymes, and electronic properties of corresponding tetrahedral compounds, which are intermediates of the hydrolytic reaction, were calculated by the CNDO/2 method. The nature of substituents and the formation of the hydrogen bond by the carbonyl oxygen atom were shown to have no sufficient influence on the charges and bond orders of the amide group. The dramatic dependence of the amide electronic state from the distort degree of its planar structure was found.

[Proteases of swine small intestine enterocytes. Kinetics of substrate hydrolysis and inhibition of aminopeptidase N from brush border vesicles].

The kinetics of hydrolysis of L-leucine p-nitroanilide and some p-nitrophenylalanine dipeptides by vesicular aminopeptidase N from the porcine small intestine brush border membrane was studied. It was shown that the catalytic properties of the vesicular enzyme are very similar to those known for its solubilized counterpart. Both enzymes are inhibited by o-phenanthroline, ZnCl2 and puromycin with Ki = 10(-5)-10(-6) M.

[Mechanisms of proteolysis].

Mechanisms of the amide bond hydrolysis catalyzed by proteolytic enzymes have been analyzed using mainly our own experimental data. The rationale for the efficiency and specificity of proteinases has been proposed that relates these features to the state of the substrate in the productive enzyme-substrate complex.

Role of intestinal brush border membrane aminopeptidase N in dipeptide transport.

The kinetics of uptake of radioactive label from [U-14C]Gly, L-[4,5-3H]Leu and the dipeptide [14C]Gly-L-[4,5-3H]Leu by the brush border membrane vesicles of porcine small intestine have been studied. The effect of aminopeptidase N inhibitors and leucine-binding protein on accumulation rates has also been tested. Comparison of the kinetic parameters for uptake and hydrolysis of Gly-L-Leu makes it possible to conclude that the dipeptide transfer includes two conjugated steps, viz.

[Evaluation of ion activity in determining time of death].

Activity of potassium ions was examined in 3 liquid media of 54 rabbit cadavers by potentiometry with the use of a potassium-selective valinomycin electrode. The reported and obtained data were used for the development of the diagnostic regression equations and the curves to define the time of death from the activity of a complex of 3 ions (potassium, sodium and hydrogen) in the blood serum, CSF and vitreous body fluid. The method is offered for appropriate trials in human cadavers.

[Problems of the epidemiology of viral hepatitis in Ryazan Province].

The analysis of some features of the course of the epidemic process of viral hepatitis on the territory of the Ryazan region is presented. Periodic rises and falls in viral hepatitis morbidity, varying in their regularity (4-6 years), have been registered in the region. The general level and the seasonal distribution of viral hepatitis morbidity are determined by the morbidity rate among children, the increase in the proportion of children of senior school age being observed in recent years.

[Mechanism of oxygen exchange in the amide group of substrates during their hydrolysis catalyzed by leucine aminopeptidase and pepsin].

Oxygen exchange in the amide group of leucine amide catalyzed by leucine aminopeptidase, and in leucyltyrosine amide catalyzed by porcine pepsin, was found to proceed mainly by the transfer of the leucyl residue onto the ammonia or tyrosine amide which are formed during the hydrolysis. Thus oxygen exchange in the non-hydrolyzed substrate can not be a proof of the tetrahedral intermediate formation in the course of the catalysis by proteolytic enzymes.

[Conductivity of bilayer lipid membranes of phosphatidic acid at phase transitions, induced by temperature and pH].

Conductivity of bilayer lipid membranes formed from synthetic phosphatic acid and its thioanalogs was studied. Conductivity of bilayer lipid membranes was shown to change spasmodically in the phase transition region. The temperature of conductivity jump decreased with pH shift from acid to alkaline region.

[Technique and methods of bronchoholography].

A new roentgenological technique of a bronchial tree examination--bronchoholography has been described. To receive holographic image of a contrast bronchial tree the authors introduced changes and additions in usual bronchography technique: a contrast bronchial tree has been recorded on a video tape of a tape recorder at the moment of deep inspiration, the patient was rotating around its vertical axis at that time. Then bronchial tree videogram has been transferred on a cine film.

[Characteristics of membrane activity of triterpene glycosides].

The membrane activity of 6 triterpenic glycosides was studied with respect to ionic permeability of the liposomes and flat bilayer lipid membranes. It was shown that the rate of the glycoside effect depended on both the sterol level in the membrane and the sterol type (cholesterol, ergosterol). The activity of cauloside C, a plant glycoside markedly depended on pH of the medium.

[Effect of polymyxin B on ion permeability of bacterial membranes].

Effect of polymyxin B on the movement of K+ and H+ in polymyxin-sensitive cells of E. coli under different metabolic states has been studied. It was shown that polymyxin B induced the efflux of K+, decreased the efflux of H+ and inhibited the consumption of oxygen in bacterial cells.

[Effect of polymyxin B on the conductivity of negatively charged bilayer lipid membranes].

Effect of polymyxin B on the planar bilayer lipid membranes (BLM) formed from synthetic phosphatidic acid has been studied. The addition of cholesterol to phospholipid in molar ratio 1 : 2 was followed by an increase of BLM conductance from 2 x 10(-8) to 3 x 10(-7) Ohm-1 cm-2. It was suggested that the observed increase of conductance was due to the fluidity of the membrane matrix in the presence of cholesterol.

Studies on the mechanisms of action of proteolytic enzymes using heavy oxygen exchange.

Transpeptidation reactions catalyzed by chymotrypsin, pepsin, leucine aminopeptidase and thermolysin have been studied in heavy oxygen water (H2 18O). The 18O incorporation into the peptide bond of transpeptidation products and into the non-hydrolyzed substrate has been measured. The rates of 18O exchange in the carboxylic groups of N-acetylphenylalanine and leucine, catalyzed by pepsin and leucine aminopeptidase, respectively, have also been determined.

[Effect of phase transition on electric capacitance of plane lipid membranes].

Effect of lipid phase transition on electric capacitance of plane lipid membranes was studied. For this purpose the capacitance of the membranes formed from solutions of saturated synthetic phospholipids in different solvent systems were measured at different temperatures. It was found that the capacitance of the membranes formed from phospholipid solution in dioxane having practically no solvent decreased at phase transition from liquid crystal state to gel.