Orientational changes of amphotericin B in Langmuir monolayers observed byBrewster angle microscopy

The morphology of amphotericin B monolayers spread at the air/water interfa ce was investigated at the microscopic level with a Brewster angle microsco pe. The images were recorded simultaneously with the surface pressure (pi)/ area (A) isotherms. The transformation from the domain-like structure to ho mogeneous solid phase was observed upon monolayer compression. Quantitative analysis was made from the measurements of relative reflectivity during mo nolayer compression/decompression. A 3-fold increase in relative monolayer thickness throughout the compression from the expanded to a condensed state is observed and related to orientational changes of the monolayer molecule s from a horizontal to a vertical position.