The origin of the diphenylhexatriene short lifetime component in membranes and solvents

Fluorescence decay of 1,6-diphenyl-1,3,5-hexatriene (DPH) was found to be bicomponental in lipid bilayers and isotropic solvents. Mean lifetime values of both components correlated with the permittivity of the solvents. Decomposition of time-resolved spectra of DPH in phospholipid vesicles revealed a significant red shift of the spectrum of the short-lived component with respect to the spectrum of the long-lived component. This indicated that part of DPH was in a hydrophilic environment, which was supported by fluorescence energy transfer experiments. We showed that the increased fraction of the short-lived component in lipid bilayers originates from the population of DPH at the membrane–water interface.