Document Type
Article
Publication Date
3-27-2025
Published In
The Journal Of Physical Chemistry B
Abstract
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 Synechocystis 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 transfer between energetically connected red Chl sites as the physical basis of singlet–singlet annihilation. The time scale of this energy transfer is faster than predicted by Förster resonance energy transfer calculations, raising questions about the physical mechanism of the process. Our results indicate distinct strategies to steer excitations through the PSI antenna; the red Chls present a shallow reservoir that direct excitations away from P₇₀₀, extending the time to trapping by the reaction center.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Sara Sohail, S. Sohoni, P.-C. Ting, L. R. Fantz, S. M. Abdulhadi, C. MacGregor-Chatwin, A. Hitchcock, C. N. Hunter, G. S. Engel, and S. C. Massey.
(2025).
"Functional Connectivity Of Red Chlorophylls In Cyanobacterial Photosystem I Revealed By Fluence-Dependent Transient Absorption".
The Journal Of Physical Chemistry B.
Volume 129,
Issue 12.
3191-3197.
DOI: 10.1021/acs.jpcb.5c00198
https://works.swarthmore.edu/fac-chemistry/302
Comments
This work is freely available under a Creative Commons license.