[Comparative study of diffusion coefficients of alpha-lactalbumins and lysozyme using polarization interferometer]. / Sravnitel'noe issledovanie koéffitsientov diffuzii alpha-laktal'buminov i lizotsima s pomoshch'iu poliarizatsionnogo interferometra.

The method of macroscopic diffusion with polarization optics has been applied to compare the translational diffusion coefficients for three proteins with similar three-dimensional structures in different conformational states. It has been shown that the values of diffusion coefficients obtained by the method are almost the same as those obtained by quasielastic light scattering. However this method is more available since it is less sensitive to aggregation and requires less amount of protein for investigation.

[A study of native streptokinase and its polymeric derivative by means of small angle x-ray scattering]. / Issledovanie nativnoi streptokinazy i ee polimernogo proizvodnogo metodom rentgenovskogo rasseianiia pod malymi uglami.

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.

[Effect of the pH of the medium on DNA conformation]. / Issledovanie vliianiia pH sredy na konformatsiiu molekuly DNK.

The hydrodynamical and optical properties of DNA were investigated in the wide-range of pH by the methods of streaming birefringence, viscometry and spectrophotometry for the different ionic strengths of environment. The measurements of the intrinsic viscosity as a function of pH allow us to determine the compactization of protonated DNA without the destruction of double-helical conformation. This transition is accompanied by a decrease in the optical anisotropy of DNA and the coefficient of molar extinction E260 (P). The increase of volume and persistence length of DNA was observed in the alkaline range of pH. Analyses of experimental data lead to an assumption that the predominant cause of these effects is the change of flexibility of DNA as a result of ionization of its bases. The data obtained were compared with those for polycationic molecules.