title: Nitroxide spin-probe study of amphotericin B-ergosterol interaction in egg phosphatidylcholine multilayers.
abstract: The interaction between the polyene macrolide antibiotic, amphotericin B, and ergosterol in egg phosphatidylcholine multilayers was investigated using head group and acyl chain nitroxide spin-labelled phosphatidylcholine as probes. At physiological concentrations of less than 15 mol% sterol in egg phosphatidylcholine multilayers amphotericin B accumulates near the head group region until an amphotericin B : ergosterol ratio of approximately 0.7 is achieved. As the proportion of amphotericin B is increased above this value, formation of an acyl chain disordering complex occurs which has an approximate antibiotic:sterol ratio of unity. Dicetyl phosphate was used to increase the solubility of ergosterol past its normal limit in pure egg phosphatidylcholine (approximately 15 mol%). At concentrations of ergosterol higher than 15 mol% a complex of two ergosterol molecules and one amphotericin B was postulated when there was insufficient antibiotic to form a 1:1 complex.
mesh_terms: D000666:Amphotericin B; D003497:Cyclic N-Oxides; D004530:Egg Yolk; D004578:Electron Spin Resonance Spectroscopy; D004875:Ergosterol; D005260:Female; D008081:Liposomes; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009761:Nystatin; D010713:Phosphatidylcholines; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D008081:Liposomes; D010713:Phosphatidylcholines; D013113:Spin Labels; D009761:Nystatin; D000666:Amphotericin B; D004875:Ergosterol