On the photochemical proton expulsion capability of fringelite D - A modelof the protist photosensory pigments of the stentorin and blepharismin types

Using simultaneous two-photon excitation of fringelite D and a fluorescence indicator embedded in a vesicle system it was demonstrated that after exci tation a proton was transferred from the pigment to the indicator similarly as recently documented for hypericin. Semiempirical AM1 calculations were used to show that the radical species formed by electron transfer from the excited pigment state constitutes an acid which is therefore well suited fo r intermolecular proton transfer. Accordingly, this process constitutes a s uited candidate for the primary phoroprocess in the signal transduction cas cade of the photosensory pigments of the stentorin and blepharismin type.