The behavior of the fluorescence lifetime and polarization of oxonol potential-sensitive extrinsic probes in solution and in beef heart submitochondrial particles.

The fluorescence polarization and lifetime of the extrinsic potential-sensitive probes oxonols V and VI have been investigated both for the dyes free in aqueous and ethanol solutions and in the presence of beef heart submitochondrial particles under resting and energy-transducing conditions. The emission lifetime of the dyes appears to be inversely related to the solvent dielectric constant and increases as the solvent is changed from an aqueous medium to ethanol to the biological membrane. The fluorescence decay curve becomes biphasic in the presence of the membrane preparation and consists of a faster decaying component, the lifetime of which is the same as that of the probe in aqueous solution and of a slower decaying component.