Revealing the Orientation of Nystatin and Amphotericin B in Lipidic Multilayers by UV−Vis Linear Dichroism

Abstract

Amphotericin B UV-Vis absorption linear dichroism data was combined with Nystatin steady-state fluorescence linear dichroism data to calculate their orientational probability density functions in multilayers of dipalmitoylphosphatidylcholine (DPPC), DPPC+cholesterol and arachidic acid+cholesterol multilayers. The cholesterol effect is striking on both the mean orientation and range of allowed orientations. The mean becomes closer to the layers normal (from 8.6°to 2.3°) in DPPC multilayers when cholesterol is present and the range (i.e., full distribution width) narrows from =40°to =10°. However, a small fraction of the antibiotic eventually remains parallel to the multilayer surface, possibly adsorbed to it. The results favor the pore model for the biochemical mode of action of the antibiotics. Moreover, a direct involvement of the sterols is suggested.

Membrane Transport

“…Nystatin (Fig. 19.19) is a channel-forming ionophore that creates a hydrophobic pore across a membrane [37,38]. Channel-forming ionophores allow for the rapid facilitated diffusion of various ions that depend on the dimensions of the pore.…”

Membrane Transport

“…Nystatin is a channel forming ionophore that creates a hydrophobic pore across a membrane [37,38]. Channel-forming ionophores allow for the rapid facilitated diffusion of various ions that depend on the dimensions of the pore.…”

Fluorescence Anisotropy to Study the Preferential Orientation of Fluorophores in Ordered Bi-Dimensional Systems: Rhodamine 6G/Laponite Layered Films

“…Fluorescence anisotropy is a powerful technique to evaluate the preferential orientation of fluorescent organic chromophores adsorbed in ordered assemblies [79][80][81][82][83][84][85][86]. Fluorescence anisotropy is based on the recording of the fluorescence intensity, both frequency-or time-resolved, for two orthogonally oriented polarizations, the parallel (I || ) and the perpendicular (I ⊥ ) orientations with respect to the direction of the polarized excitation light (Fig.…”