Energy transfer from phycobilisomes to photosystem I at room temperature

Abstract

The phycobilisomes function as the primary light-harvesting antennae in cyanobacteria and red algae, effectively harvesting and transferring excitation energy to both photosystems. Here we investigate the direct energy transfer route from the phycobilisomes to photosystem I at room temperature in a mutant of the cyanobacterium Synechocystis sp. PCC 6803 that lacks photosystem II. The excitation dynamics are studied by picosecond time-resolved fluorescence measurements in combination with global and target analysis. Global analysis revealed several fast equilibration time scales and a decay of the equilibrated system with a time constant of ≈220 ps. From simultaneous target analysis of measurements with two different excitations of 400 nm (chlorophyll a) and 580 nm (phycobilisomes) a transfer rate of 42 ns-1 from the terminal emitter of the phycobilisome to photosystem I was estimated.

Inhomogeneous energy transfer dynamics from iron-stress-induced protein A to photosystem I

“…It exceeds by orders of magnitude the timescale of EET from the phycobilisomes to PSI, which has recently been determined to be in the range of 200 ps in Synechocystis sp. PCC 6803 ( Biswas et al., 2024 ). It is also significantly faster compared to EET from the peripheral light-harvesting antenna complex of PSI in higher plants ( Akhtar et al., 2018 ; Croce and Van Amerongen, 2020 ).…”