Fluorescence resonance energy transfer from a β-carboline analogue to a cationic photosensitizer in aqueous solution

Fluorescence resonance energy transfer from a potent bioactive non-ionic molecule, 3-acetyl-4-oxo-6,7-dihydro-12H indolo[2,3-a]quinolizine, to a cationic fluorophore, phenosafranin, has been investigated Using steady state absorption as well as steady-state and time-resolved fluorescence techniques. From the quenching of the donor fluorescence by the acceptor, Stern-Volmer constant has been determined. The energy transfer process follows a long range dipole-dipole interaction mechanism. The energy transfer efficiency, the critical energy transfer distance and the distance between the acceptor and the donor have been determined for the fluorescence resonance energy transfer process.