Abstract
1. 1. Filipin complex, filipin II, filipin III, nystatin, etruscomycin, and pimaricin at concentrations of 10−5 M were able to disrupt bimolecular lipid films containing lecithin and cholesterol in a 1:1 molar ratio.
2. 2. The above antibiotics were not able to disrupt lecithin bilayer membranes at concentrations of 4.0·10−5-6.25·10−5 M.
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However, filipin complex and nystatin at higher concentrations (10−4-10−2 M) affected lecithin bilayers in the absence of cholesterol.
3. 3. Derivatives of filipin complex (perhydrofilipin and irradiated filipin), which have little or no biological activity, affected neither lecithin-cholesterol, nor lecithin bilayer membranes at concentrations of 4.0·10−5 M, but disrupted both types of bilayer films at concentrations of 10−3 M.
4. 4. Filipin II, filipin III, filipin complex, and amphotericin B could reduce d.c. resistances in decreasing order when added to one side of lecithin-cholesterol bilayer membranes generated in 0.1 M NaCl solutions. Filipin I, filipin IV, nystatin, pimaricin, and etruscomycin did not show this property. The antibiotics did not affect the d.c. resistances of lecithin bilayers.
5. 5. Addition of nystatin to one side of lecithin-cholesterol bilayer membranes generated in 0.1 M NaCl solutions, did not affect the electrical resistances. When added to both sides of these bilayers, however, nystatin reduced the d.c. resistance appreciably.
6. 6. When added to the film-forming solution, filipin III, filipin II, filipin complex, and nystatin were able to reduce the d.c. resistance of lecithin-cholesterol bilayer membranes in the order listed.
7. 7. The d.c. resistance of lecithin-cholesterol bilayers generated in 0.1 M NaCl and treated with either filipin complex, filipin II, filipin III, nystatin, or primaricin was much lower (104-105 ω·cm2) in the presence of Ca2+, but was not affected in the presence of a variety of other cations and anions. Transference number measurements showed that lecithin-cholesterol bilayers, when treated with the polyenes mentioned, become cation-selective, particularly affecting the transference numbers of Ca2+.
8. 8. The d.c. resistance of lecithin-cholesterol bilayers generated in 0.1 M NaCl and treated with amphotericin B, was extremely low in the presence of NO3−, SO42−, or HPO42−, but not in the presence of Ca2+ or other cations. Transference number measurements demonstrated that amphotericin B renders lecithin-cholesterol bilayers anion-selective.
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