Non-Foerster fluorescence quenching of trans-etiochlorin I by magnesium octaethylporphyrin in phosphatidylcholine vesicles. Evidence for a statistical pair energy trap

Abstract

Fluorescence quenching of trans-etiochlorin I (C) by magnesium octaethylporphyrin (P) has been studied in small (approx.250 A in diameter) phosphatidylcholine vesicles. It is shown that the quenching is due to the formation of a nonfluorescent statistical pair energy trap between P and C with a critical separation distance between 10 and 18 A. The formation of P/sup +/ as the result of the flash photolysis of C in vesicle suspensions containing both P and C in addition to an electron acceptor demonstrates that excitation of this trap results in an electron transfer from P to C. 31 references, 5 figures.