Fluorescence decay and depolarization of probes in membranes

摘要

Radiative decay rate depends on the efficiency of coupling between the emission dipole and the electromagnetic field. Therefore, in optically discontinuous and/or anisotropic environments the radiative rate is dependent on the orientation of the emission dipole. Single-bilayer phospholipid membranes are interesting systems for the study of this phenomenon because in these systems the functional dependence of the radiative rate is simple and the effect is stronger than in liquid crystals. The orientational dependence of the radiative rate results in a non- exponential total fluorescence intensity decay. Orientational distribution of the probe in the gel-phase membrane can be determined from the total intensity decay. In the liquid-phase membrane the coupling between decay and rotation leads to a polarized intensity decay behavior entirely different than that in isotropic media. Experimental data are consistent with every theoretical prediction.