Paramagnetic fluorescence quenching in a model membrane: a consideration of lifetime and temperature

Abstract

To expand our understanding of paramagnetic quenching in membranes, the relationship between fluorophore excited-state lifetime (τ), temperature, and the collisional quenching was studied. Specifically, the ability of tempo to quench the steady-state and time-resolved emission from five lipophilic fluorophores (diphenylhexatriene, perylene, phenanthrene, pyrene, and triphenylene) partitioned into egg phosphatidylcholine (EggPC) liposomes was examined. Also, the temperature dependence of spin-labeled androstane to quench the emission (steady-state and time-resolved) from perylene in EggPC liposomes was determined. Unexpectedly, in EggPC liposomes, the apparent quenching efficiency decreased with increasing τ until the effect leveled off above ∼20 ns. Moreover, in EggPC liposomes, dynamic quenching decreased with increasing temperature. The results suggest that in membranes, paramagnetic quenching is more complex than generally recognized.