Nanosecond to microsecond time-resolved spectroscopy in the 420 − 520 nm spectral range has been used to study the formation and decay of antenna carotenoid triplet states in photosystem I particles from Synechocystis sp. PCC6803 at 298 K. From global analysis of the transient absorption data, three decay phases with lifetimes of 30, 300, and 6000 ns, were obtained.
The flash intensity dependence of the phases, along with the spectral profiles indicate that the 30 ns and 6 µs phases are associated with the formation and decay of an antenna carotenoid triplet state, respectively. The 300- ns phase is associated with electron transfer from A1 – to FX. In menB– PSI particles from S6803 the carotenoid composition is altered compared to that of wild type PSI, and the carotenoid triplet state decay time decreases to ~2.3 µs.
Hiroki Makita and Gary Hastings (2018) Nanosecond time-resolved absorption difference spectroscopy for the study of carotenoid triplet states in photosystem I photosynthetic reaction centers, Frontiers in Science, Technology, Engineering and Mathematics, Volume 2, Issue 3, 138-147