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

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 T9ps and T62ps (τF=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 τFs were measured at delay times (td=0.05–90.5 ms) by a gated streak camera synchronized to a 626-nm picosecond laser. The td dependencies of the fluorescence of T9ps and T62ps were identical with the behaviors of the photointermediates O and Q, respectively.