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Zeta-potential of n-alkane droplets, formed by fatty acids, were studied in model systems of culture liquid of yeasts (Candida maltosa) capable of utilizing n-alkanes. The value of zeta-potential was found to depend on the droplet size. The negative zeta-potential of submicron droplets was so high that it prevented the droplets from being coagulated with cells possessing a high negative zeta-potential. The dominant role of submicron n-alkane droplets in the kinetics of yeast growth could be accounted for by the existence of a mechanism regulating contact interactions of individual cells with the droplets followed by uptake of the substrate.

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Influence of pH, temperature and oleandomycin concentration on distribution of the antibiotic in the methylene chloride-aqueous medium system was studied. It was shown that the oleandomycin distribution coefficient did not depend on the antibiotic concentration within the ranges of 2000 to 20,000 micrograms/ml. An equation defining relationship between the oleandomycin distribution coefficient and pH of the aqueous phase is presented.

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Ageing of oleandomycin preparations was studied. Certain biologically inactive components accumulating on storage of the preparations were isolated and investigated. A scheme for ageing of oleandomycin phosphate preparations is described. The scheme includes cleaving up of the water molecule at C11 and cleaving by the epoxide ring at the early stages and hydrolysis by the glycoside bonds at the later stages.

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Regularities of dissociative ionization of compounds belonging to the oleandomycin group were studied. Mass spectra of oleandomycin and some of its derivatives including anhydrooleandomycin, oleandomycin chlorhydrine, desoleandomycin, oleandomycin oxide, trimethylsilyl and acetyl derivatives were analyzed comparatively. Directions of disintegration with breakage of the glycoside bonds, macrolactone and carbon cycles were detected. The data are useful in structural analysis of not described oleandomycin-related compounds formed during biosynthesis and isolation of the main product.

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Roseofungin, a pentaen was used as an example in investigation of certain characteristics of inactivation of polyenic antibiotics. An inactivation product of the antibiotic having no antiviral or antimycotic activity was isolated by TLC and column chromatography on Sefadex LH-20. UV, IR and EPR spectroscopy showed that this product was cys-tetraen without conjugation of the lactone carbonyl to the polyenic system.

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The sterol composition of nystatin-sensitive and nystatin-resistant strains of Saccharomyces cerevisiae was being studied by gas-liquid chromatography and mass-spectroscopy. The synthesis of ergosterol is completely suppressed in polyene-resistant mutants. Three sterols derived from cholesterol were identified in the mutants: cholesta-8,24-diene-3 beta-ol, cholesta-5,7,24-triene-3 beta-ol, and cholesta-5,7,22,24-tetraene-3 beta-ol.

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Extraction of CuCl2, NiCl2, CoCl2 and MnCl2 from the aqueous phase to the organic gramicidin S containing phase (the phase ratio of 1:1) was studied with the method of molar ratios at constant concentrations of the salts and changing concentrations of the antibiotic. The composition of the forming intracomplex compounds was determined with the equilibrium shift method. It was shown that 2 ions of chlorine and 2 molecules of gramicidin S bound with 1 ion of the metals. The extraction constants were measured. The complex compounds of gramicidin S with copper chloride were the most stable.

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The acid-base transformations of the gramicidin S molecule in water were studied. The protonization constants of the antibiotic amino group were calculated by the data of the potentiometric titration and the antibiotic distribution in the system of chloroform-water: K1 1.55 X 10(10), K2 1.38 X 10(6), the logarithm of the distribution coefficient of gramicidin S in the system of chloroform-water (1:1) lg alpha G 4.10. By the same data the constants of water solubility of gramicidin S base (1.02 X 10(7) mol/l), gramicidin S monohydrate (1.06 X 10(-4) mol/l) and gramicidin S dihydrochloride (2.08 X 10(-4) mol/l) were calculated.

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The ability of some proteins to bind cholesterol was accompanied by a decrease of turbidity of aqueous cholesterol suspensions and correlated with a quantity of arginine residues in them. Maximum clearing of aqueous cholesterol suspensions at the addition of proteins containing equimolar arginine concentrations was observed in the presence of apoproteins E and A-I. Optical rotatory dispersion spectra of apoprotein E, polyarginine and histone H3 have shown the influence of sterol on the secondary structure of apoprotein E only.

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An approximation of isolated spin pairs is used to obtain the equation for PMR line shape of lipid bilayers. The internuclear vector order parameter dependence on the position of the proton pair of lipid molecule is taken into account. Good agreement with experimental curves leads to the conclusion that the main reason for the unusual PMR line shape of lipid bilayers is decrease of order parameters on approaching hydrophobic tails of lipid molecules of bilayer.

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Levorin destruction in oxygen, argon or air at various temperature levels was studied. It was found that destruction of the antibiotic molecule was mainly due to its interaction with oxygen. As a result the heptaenic chromophore was oxidized and triene and tetraene formed. Oxidation of levorin was accompanied by splitting out of paraaminoacetophenone. Destruction of levorin in the absence of oxygen was retarded.

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Characteristic features of interaction of nystatin with bivalent copper salts in water, methanol and dimethylsulfoxide were studied. It was shown that stable compounds of copper and nystatin at ratios of 1 : 2 and 1 : 4 formed in the above solvents. The antibiotic in these compounds was in an inert, native or activated state. Physicochemical and biological properties of the compounds were investigated.

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Comparative stability of crystalline and amorphous oleandomycin phosphate was studied. It was shown that the structure and humidity of oleandomycin phosphate were among the main factors determining its stability. Crystalline oleandomycin phosphate was highly stable and the effect of humidity on its stability was relatively low. A significant effect of humidity on the stability of amorphous oleandomycin phosphate was observed.

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The derivatographic investigation of high temperature of inosine and its 8-substituted derivatives showed that the process of destruction involved 2 stages: low temperature endothermic decomposition at 120-220 degrees C without liberation of gaseous products (stage I) and high temperature exothermic decomposition to form water (stage II). The presence of electronegative 8-substituents in the inosine molecule made easier the cleavage of the N-glycoside link. This allows the conclusion that the reaction involved formation of intermediate ionic compounds based on ribose and hypoxanthine.

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Changes in the acid-base characteristics of levorin during its inactivation are discussed. It is shown that with a decrease in the biological activity a change in the basic characteristics of the levorin amino sugar moiety takes place. The kinetic studies with model compounds, i. e. octaenic alcohol and glucosamine showed that the processes of their oxidation were interrelated. Oxidation of the amino sugar played the role of an inducing factor in oxidation of the polyenic chromophore and in addition impaired correlation between the extinction specific coefficient of levorin and its biological activity.

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Marketed oleandomycin phosphate, as well as the International Standard of oleandomycin (Great Britain, the 1st Int. Std., 1964) were studied with a purpose of determining their composition. The components were separated by liquid chromatography on columns with Sefadex LH-20 using 50 per cent ethanol as an eluent. The Lowry method using the biuret test and assays of the amino acids in the hydrolysates were used to show for the first time that marketed oleandomycin and its International Standard contained an admixture of the peptide nature. The data of the amino acid assays suggest that the admixture and oleandomycin is a fixed complex (adduct).

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The results of studying free radicals of some polyenic antibiotics with the EPR method are presented. It is shown that the number of free radicals increased by 100 per cent with a 2-fold decrease in the biological activity. A qualitative change in the EPR spectrum due to the presence of a new radical type was also observed. The changes in the spectral characteristics of levorin allowed one to demonstrate that breaking of the links and formation of the polymer products during oxidative destruction of the polyenic chromophore resulted from attachment of the radicals through the antibiotic double bonds. The data correlate with the results of the quantum-chemical evaluation of the polyenic chromophore.

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