AUTHOR=Biswas Avratanu , Akhtar Parveen , Lambrev Petar H. , van Stokkum Ivo H.M. TITLE=Energy transfer from phycobilisomes to photosystem I at room temperature JOURNAL=Frontiers in Plant Science VOLUME=Volume 14 - 2023 YEAR=2024 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1300532 DOI=10.3389/fpls.2023.1300532 ISSN=1664-462X 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 timeresolved 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.