biostudies-literatureSohail SHEuropean Research CouncilBasic Energy SciencesU.S. Department of DefenseWelch FoundationDivision of Materials ResearchRoyal SocietyNational Defense Science and Engineering GraduateAir Force Office of Scientific ResearchBiotechnology and Biological Sciences Research CouncilNational Science Foundation3191-3197https://www.ebi.ac.uk/biostudies/studies/S-EPMC11956136biostudies-literatureUnknown129(12)External stressors modulate the oligomerization state of photosystem I (PSI) in cyanobacteria. The number of red chlorophylls (Chls), pigments lower in energy than the P₇₀₀ reaction center, depends on the oligomerization state of PSI. Here, we use ultrafast transient absorption spectroscopy to interrogate the effective connectivity of the red Chls in excitonic energy pathways in trimeric PSI in native thylakoid membranes of the model cyanobacterium <i>Synechocystis</i> sp. PCC 6803, including emergent dynamics, as red Chls increase in number and proximity. Fluence-dependent dynamics indicate singlet-singlet annihilation within energetically connected red Chl sites in the PSI antenna but not within bulk Chl sites on the picosecond time scale. These data support picosecond energy The journal of physical chemistry. BFunctional Connectivity of Red Chlorophylls in Cyanobacterial Photosystem I Revealed by Fluence-Dependent Transient Absorption.PMC11956136DMR-1420709OMA-2121044FA9550-14-1-0367FA9550-18-1-0099854126DE-SC0020131AF-0005URF\R1\191548BB/M000265/1N00014-15-1-0048N00014-16-1-2513DE-SC0001035190035932 CFR 168aTing PCHunter CNMassey SCFantz LRSohail SHEngel GSHitchcock AMacGregor-Chatwin CSohoni SAbdulhadi SMfalseFunctional Connectivity of Red Chlorophylls in Cyanobacterial Photosystem I Revealed by Fluence-Dependent Transient Absorption.External stressors modulate the oligomerization state of photosystem I (PSI) in cyanobacteria. The number of red chlorophylls (Chls), pigments lower in energy than the P₇₀₀ reaction center, depends on the oligomerization state of PSI. Here, we use ultrafast transient absorption spectroscopy to interrogate the effective connectivity of the red Chls in excitonic energy pathways in trimeric PSI in native thylakoid membranes of the model cyanobacterium <i>Synechocystis</i> sp. PCC 6803, including emergent dynamics, as red Chls increase in number and proximity. Fluence-dependent dynamics indicate singlet-singlet annihilation within energetically connected red Chl sites in the PSI antenna but not within bulk Chl sites on the picosecond time scale. These data support picosecond energy 2025-01-01T00:00:00Z2025 Mar2026-06-02T06:33:21.691Z2026-04-15T03:15:23.946ZS-EPMC119561364010081010.1021/acs.jpcb.5c00198