Picosecond-millisecond dual-time-base spectroscopy of fluorescent photointermediates formed in the purple membrane of Halobacterium halobium

Abstract

Dual-time-base fluorometry to measure both fluorescence lifetimes and the reaction kinetics of their origins was applied to the identification of two fluorescence (>660 nm) species T 9ps and T 62ps ( τ F=9±2 and 62±2 ps, respectively) in the purple membrane of Halobacterium halobium in the photostationary state. Photocycles were driven with a 532-nm nanosecond laser and the τ Fs were measured at delay times ( t d=0.05–90.5 ms) by a gated streak camera synchronized to a 626-nm picosecond laser. The t d dependencies of the fluorescence of T 9ps and T 62ps were identical with the behaviors of the photointermediates O and Q, respectively.