Light-scattering effects in the measurement of membrane microviscosity with diphenylhexatriene

Data from several membrane systems are presented to confirm an empirical means of correcting diphenylhexatriene fluorescence for depolarization caused by sample turbidity. The depolarization proportionally constants obtained are not equal, but are shown to vary with (a) the physical state of the membrane, (b) the cholesterol content of the membrane, (c) the protein content of the membrane, and (d) the method of membrane preparation or isolation. It is concluded that depolarization corrections must always be considered when diphenylhexatriene fluorescence anisotropy is used to compare the fluidities within different membrane bilayers.