[Role of sterol structure in complex formation with polyene antibiotics].

The capacity of sterols of different structure being components of artificial bilayer lipid membranes for formation of complexes with polyenic antibiotics, such as amphotericin B, nistatin and levorin was studied. It was shown that sterols delat 5,7-dienic systemin ring B, ergosterol and cholesta-5,7,22-trien 3 beta-ol had the highest affinity to all the 3 antibiotics, while sterols with one double bond in ring B, i. e. cholesterol and brassicasterol had less affinity and sterol without any double bonds in the molecule i.e. 5alpha cholestan 3beta-ol had the least affinity. It was supposed that delta 5,7-sterols had the highest affinity to polyens because of the fact that atoms C-5, C-6; C-7 and C-8 in ring B were practically situated in one plane in contrast to sterols with completely saturated ring B situated in the "conformation chair". Because of this interaction between delta 5,7-sterol ring B and the same flat polyenic site of the antibiotic molecule is sterically most firm since maximum contact is possible between two planes. It was noted that affinity of sterol to the polyenic antibiotics was higher if there were a double bond at 22-23 and methyl group at C-24 in the sterol side chain.