Evidence that nystatin may not form channels in thin lipid membranes

The mechanism of nystatin-induced conductance increases in planar bilayer membranes formed from lecithin/cholesterol (1:1) has been examined by spectral analysis of kinetic fluctuations. Lorentzian components of the power spectrum, characteristic of channel activity, were not observed for nystatin-doped membranes. Instead, the noise associated with this system (approximately 10(-27)A2/Hz) was in better agreement with that expected of a carrier mechanism involved in the transport of single charges in uncorrelated fashion. The implications of this result with respect to previous models of nystatin-induced conductance increases are discussed.