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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.

The influence of aeration, pH and iron concentration on the growth of yeast C. lipolytica 704 on the hexadecane medium and on the synthesis of citric and isocitric acids was investigated. The yeast synthesized citric acids actively during intensive aeration. The acid formation was strongly dependent on the medium acidity: pH 6.0 was most favourable for the synthesis of citric acids. The Fe concentration influenced significantly the ratio of the acids synthesized. At a low concentration of iron (0.005 mg Fe/l) equal amounts of citrate and isocitrate were formed; at an increased concentration isocitrate was in predominant formation.

Experiments were carried out to examine the capacity of two strains of Candida lipolytica, producing citric and isocitric acids in the alkane and glucose containing media, to grow on different two- and three-carbon compounds. The strains did not grow on oxalate, glyoxalate, glycolate, malonate or propionate. When cultivated in the media containing acetate, ethanol, glycerol, glucose or hexadecane, supersynthesis of the acids started after complete consumption of the nitrogen source and resultant delay of the culture growth. Either strain discharged the two acids in a proportion that depended on the strain nature and the type of the carbon source. The mutant strain produced only citrate while the wild-type synthesized both citrate and isocitrate, the ratio of which was related to the nature of the carbon source utilized.