[Use of arylsulfenylchlorides for cleaving fibrinogen at methionine residues]. / Primenenie arilsul'fenilkhloridov dlia rasshepleniia fibrinogena po ostatkam metionina.

Conditions for the fibrinogen fragmentation with 2-pyridyl-or o-nitrophenylsulfenylchloride were proposed. Resulting mixture of fragments is identical to the mixture prepared by the cyanogen bromide treatment and is suitable as supplementary analytical reagent in the determination of the tissue plasminogen activator (TPA) activity with a chromogenic substrate.

[The heterogeneous character of protein modification during substitution of their amino groups. Acylation of alpha-chymotrypsin]. / Geterogennyi kharakter modifikatsii belkov pri zameshchenii ikh aminogrupp. Atsilirovanie al'fa-khimotripsina.

Thin-layer isoelectric focusing of chymotrypsin modified by stepwise acylation with acryloyl chloride or maleic anhydride revealed a high heterogeneity of modification products, with a maximal number of components near 50% of substituted amino groups. Disc electrophoresis failed to establish the products diversity and could not therefore be used for heterogeneity control. The activity of the modified enzyme towards proteins and low molecular weight substrates depended on the modification reagent and correlated with the electrostatic enzyme--substrate interaction. The low hydrolytic activity towards N-acetyl-L-tyrosine p-nitroanilide was due to the increase in the Michaelis constant; the value of the catalytic constant remained unchanged.

[Preparation of subtilisin BPN' and dextran conjugates]. / Poluchenie konbiugatov subtilizina VPN' s dekstranami.

The conditions for subtilishine BPN' binding with bromocyanogen activated dextranes have been selected. The dependence of the enzyme activity and stability from pH and temperature levels has been studied. The stability of a modified enzyme during storage in solution is increased as compared with that of the native enzyme due to a decrease in the autolysis rate. On the basis of diffusion coefficients and sedimentation constants of conjugates, absolute values of their molecular weights have been computed.

[Effect of temperature and concentrations of initial components on synthesis of internucleotide bond catalyzed by pancreatic ribonuclease]. / Vliianie temperatury i kontsentratsil iskhodnykh komponentov na sintez mezhnukleotidnoi sviazi, kataliziruemi pankreaticheskoi ribonukeazoi

The synthesis of cytidylyu-(3,-5,)-cytidine (CpC) catalyzed by pancreatic ribonuclease at 23 degrees, 0 degrees, and -15 degrees C in Tris-HCl-buffer was compared with that in aqueous propan-2-0. The data obtained show that the increase in the yield of oligonucleotides in aqueous buffer at -15 degrees, observed earlier is rather a result of the concentration change in the reaction mixture caused by the freezing of water than by a temperature fall from 0 to -15 degrees. A 4-fold increase in the initial concentrations of the substrates and ribonuclease with respect to the concentrations used earlier leads to the yield of CC in a homogeneous solution at 0 degrees close to is yield found in the frozen mixture at -15 degrees.