Fluorometric evidence for the binding of cholesterol to the filipin complex.

The data show that the filipin complex in water has a characteristic fluorescence spectrum with a broad emission maxima at 497nm. Addition of cholesterol to the aqueous solution decreases the absorbance, the corrected fluorescence, and the partial quantum efficiency. The reduction in partial quantum efficiency, which is independent of the concentration of filipin, is definitive evidence that the filipin complex interacts with sterols in aqueous solution. The data indicate that changes in fluorescence may be a sensitive tool for monitoring the interaction of filipins with sterols.