Vectorial PET in LB bilayers and in vesicles: Nanosecond fluorescence and laser flash-photolysis investigation

Vectorial photoinduced electron transfer was investigated in Langmuir-Blodgett bilayers and in vesicles with the same phospholipid composition. The donor was covalently bound to one of the hydrophobic chains of the phospholipid in the mimetic membrane, whereas the acceptor was adsorbed at the polar head group surface. The location of the redox couple was preliminarily determined studying the photophysical properties of the donor in the phospholipid bilayer as well as the process of adsorption of the acceptor at the phospholipid-water interface. The photoinduced electron transfer reaction was studied measuring the quenching of pyrene fluorescence in the presence of increasing concentrations of acceptor, the process was studied both with steady-state and time-resolved fluorescence emission in the nanosecond time scale. The reaction transient species formed upon photoexcitation were identified performing nanosecond laser-flash photolysis experiments in vesicle systems. The dynamics of the charge recombination process following photoinduced electron transfer, was investigated studying the kinetic of decay of the absorption signal of the transient species.