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Biomedical subjects

B V Moskvichev

Publications and source records attributed to B V Moskvichev.

At least 19 recordsLinked to original sources
PubMed1990

Study of the structure of streptokinase conjugates with a hydrophilic vinylpyrrolidone copolymer.

The modification of streptokinase by a synthetic N-vinylpyrrolidone copolymer leads to formation of conjugates varying in structures according to the proportions of the components in the reaction medium. Based on data obtained from spectrophotometry, as well as sedimentation and diffusion analyses, it is shown that in the presence of excess protein in the reaction medium, formation of the main chain takes place via the copolymer associated with several protein globules. Under conditions of excess modifier copolymer, either single-site and/or multiple-site bonding is possible for the protein backbone, depending on the molecular weight of the copolymer. One of the models for the conjugates obtained in this manner has been corroborated by small-angle X-ray scattering data. CD spectral analyses has been performed in order to demonstrate that covalent modification does not alter the secondary structure of streptokinase in the conjugate whereas the tertiary structure undergoes local changes in conformation.

Circular Dichroism↗
PubMed1985

[The conformation properties and conformation stability of streptokinase and its polymer derivative].

The properties and conformational stability of the proteinaceous activator of fibrinolysis--native streptokinase--and its derivative obtained by modification with a linear hydrophilic copolymer based on N-vinylpyrrolidone, were studied by the circular dichroism method. It was shown that polymeric modification of streptokinase had no effect on the secondary structure, while the conformational stability of the modified protein to urea was higher than that of the native one. Studies on thermal stability of both native and modified forms of streptokinase showed that the inactivation rate was lower in the modified form as compared to the native one.

Amino Acid Sequence↗
PubMed1981

[Effect of chemical modification on proteinase interaction with inhibitors, on their coagulability and acute toxicity].

A comparative study of terrylytin, trypsin and products of their covalent binding to human serum albumin was carried out. Modification caused a decrease of the affinity of both enzymes for proteinase inhibitors from the blood. The inhibition constant for terrylytin was increased 3-4-fold, that for trypsin - by 2 or 3 orders. The recalcification time of human blood plasma in the presence of terrylytin remained practically unchanged after enzyme chemical modification. Trypsin binding to albumin decreased its coagulability. Preparations of modified enzymes were characterized by a decreased acute toxicity, this effect being especially well-pronounced in the case of trypsin. The decrease of terrylytin toxicity due to modification can be accounted for by a decrease in its affinity for alpha2-macroglobulin. The decrease of trypsin toxicity is apparently due to a decrease of its coagulability due to binding to albumin.

Amylases↗
PubMed1981

[Effect of polymeric modification on specific properties of soya bean inhibitor].

Chemical modification of the trypsin inhibitor from soya beans by a hydrophilic synthetic copolymer of N-vinylpyrrolidone was studied. The optimal conditions for modification (pH, ratio of reactants, reaction time) were established. The soluble polymeric forms of the inhibitor differing in the number of covalent bonds with the copolymer were obtained. An affinity adsorbent for isolation of trypsin was prepared by adsorption of the polymeric form on silochrome.

Chromatography, Affinity↗
PubMed1981

[Mechanism of thermal denaturation of native trypsin and trypsin modified by neutral soluble polymer].

The thermal denaturation of trypsin solutions and trypsin vinylpyrrolidone-acrolein copolymer conjugate was studied within the temperature range of 37.5-96 degree. pH 4.5. A mechanism for trypsin thermal denaturation based on its ability to form dimers and determining the minimal stability of the enzyme at 66 degree and its maximal stability at 74 degree is proposed. The thermal denaturation of the trypsin conjugate is of a different type, which depends on the changes in the thermal denaturation mechanism due to its incapability to form dimers. A decrease in the activation and thermodynamic parameters of the enzyme denaturation during its modification is due to the approximation of the protein structure to that of the denatured form, eventually resulting in the enzyme destabilization. The increased stability of the modified protein to the denaturating effects of low temperatures is due to the changes in the denaturation mechanism induced by enzyme modification.

Acrolein↗
PubMed1980

[Physico-chemical properties of terrylytin modified by a copolymer based on vinylpyrrolidone].

The proteolytic activity of terrylytin produced by the culture of Asp. terricola and modified by a water-soluble copolymer of vinylpyrrolidone and acrolein remained unchanged after enzyme modification. Using micro-thin layer chromatography, it was shown that the bulk of the epsilon-amino groups of lysine residues of the protein enter the reaction with the aldehyde groups of the polymeric matrix. The sedimentation and diffusion patterns of the polymerenzyme adduct demonstrated that the molecular weight of the modified enzyme is the total of molecular weights of its constituent components. Evidence from viscosimetry and gel chromatography allowed to develop a hydrodynamic model of the macromolecular product. It was shown that the rate of the enzyme inactivation in the solution calculated from the first order reaction equation depends on the nature of the enzyme electrochemical microenvironment. Under conditions close to physiological ones the rate inactivation constant for terrylytin modified by a neutral polymeric matrix is 10 times less than that for the native enzyme. At the isoelectric point (pH 4,6) a positively charged polymeric form of terrylytin is found to be the most stable one. The pH and temperature optima for casein hydrolysis remained unchanged throughout polymeric modification. The polymeric membrane did not hamper the diffusion during approximation of the substrates (casein and insulin) to the enzyme molecule during the catalytic act, which manifested itself in a constancy of Michaelis curves. Terrylytin modification by a copolymer causes an increase of stability with respect to trypsin proteolysis and a decrease of human blood plasma affinity for the inhibitors. The apparent inhibition constants for modified enzyme forms do not depend on the nature of electrochemical microenvironment and exceed that for native terrylytin 10-fold.

Amylases↗
PubMed1979

[Kinetics of low molecular weight substrate hydrolysis by immobilized trypsin].

The catalytic properties of trypsin immoblized on silochrome were studied in a flow reactor with replacement. The hydrolysis of methyl ester N-n-tosyl-L-arginine obeys the Michaelis--Menten kinetics. The apparent K'm value for the system with immobilized trypsin is considerably lower than for native trypsin. The K'm value was decreased with an increase in the rate of the substrate flow through the reactor or when smaller-sized silochrome granules were used. It is assumed that the apparent K'm value for the immobilized system is due to diffusion. The effects of diffusion on the catalytic properties of the immobilized enzyme were estimated.

Enzymes, Immobilized↗
PubMed1978

[Some peculiarities of trypsin and heparin interaction].

The interaction of trypsin with an acid polysaccharide, heparin, at pH 4.2 and 8.0 is studied. Heparin is found to destabilize the enzyme under condition of both autolytic denaturation (pH 8.0) and thermoinactivation (pH 4.2). Data on trypsin inactivation kinetics suggest that the stage of forming molecular complexes with different contents of trypsin and heparin precedes the stage of the enzyme denaturation. Maximal trypsin inactivation rate takes place under equimolar enzyme:heparin ration.

Chemical Phenomena↗
PubMed1977

[Some physicochemical properties of modified trypsin].

Physico-chemical properties of trypsin covalently bound with human serum albumin by glutaric aldehyde have been studied. The modification of the enzyme practically caused no changes in the pH optimum of trypsin. The inhibition of modified trypsin by inhibitors from soy beans and human blood serum has been also studied. The apparent inhibition constants have been calculated. The modification has been shown to result in a deceleration of autolytic degradation. The autolysis rate constants have been calculated at 50 degrees C.

Chemical Phenomena↗
PubMedDate not supplied

[Study of ultrafiltration of trypsin solutions].

The dependence of the rate of trypsin ultrafiltration on the concentration, pressure and structure of membranes was studied. During ultrafiltration of diluted trypsin (0.3 mg/ml), water and sodium chloride the flow rate increased linearly with a pressure increase in the range of 0.4-4.2 kg/cm2. During ultrafiltration of trypsin solutions of a concentration of 1 mg/ml and over at a pressure of 2-3 kg/cm2 deviations from linear proportionality occurred which enhanced with an increase in the protein concentration and a decrease in membrane permeability.

Binding Sites↗
PubMedDate not supplied

[Denaturation of the alpha-amylase of Bacillus subtilis in an acid medium].

By fractionation of purine compounds (sorbtion on the cation exchange resin KU-2 (H+), extraction, precipitation of purine compounds as Ag-complexes) a "purine fraction" of the culture liquid epiphytic bacteria No. 703 isolated from barley overground organs was obtained. The presence of isopentenyl cytokinins was demonstrated by quality reactions of the purine fraction with aromatic amines and phenols as well as by the values of Rf and UV spectrum of individual compounds examined by paper chromatography of the purine fraction.

Amylases↗
PubMedDate not supplied

[A study of native streptokinase and its polymeric derivative by means of small angle x-ray scattering].

The gyration radius (R0) of native streptokinase (SK) was found to be R0 = (40 +/- ) A by small-angle X-ray scattering. Experimental hydrodynamic characteristics of SK were S0(20),W = (2.8 +/- 0.1)S; D0(20),W = (6.0 +/- 0.5) x 10(-7) cm2/s; [n] = 0.12 dl/g. The molecular weight of the enzyme was found to be 44,000. The values of the form factor R0/Rsphere = 2.1 and the frictional ratio f/f0 = 1.5 indicate considerable anisometry of the SK molecule. Basing on the curves of small-angle X-ray scattering of SK modified with a synthetic linear copolymer of N-vinylpyrrolidone (P) at a molar ratio SK less than P, a structural model of the conjugate was proposed. The modified form consisted of a dense nucleus covered with a diffuse polymeric membrane. In accordance with the model, R0 of modified SK and of the whole conjugate were found to be R0nucleus = (34 +/- 2) A and R0conjugate = (114 +/- 5)A.

Polymers↗
PubMedDate not supplied

[Chemical modification of proteolytic enzymes by low molecular weight agents].

Low-molecular modification of proteolytic enzymes with aldehydes and anhydrides of carboxylic acids as well as with 2,4,6-trinitrobenzene sulphonic acid was studied. Specific activities of the enzymes were found to be dependent on the modification degree of their amino groups. The retaining of high activities in the region of low extents of enzyme modification enabled biocatalysts with activities similar to those of the native enzymes to be prepared.

Aldehydes↗