期刊
BIOPHYSICAL JOURNAL
卷 118, 期 2, 页码 337-351出版社
CELL PRESS
DOI: 10.1016/j.bpj.2019.11.3391
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资金
- Russian Science Foundation [RSF 19-14-00366]
- Gibson Family Foundation
- Dr. Donald L. Akers Faculty Enrichment Fellowship
- National Science Foundation [DGE-0801470, EPS-1004083]
- University of Tennessee at Knoxville/Oak Ridge National Laboratory Science
Cyanobacterial photosystem I (PSI) functions as a light-driven cyt c(6)-ferredoxin/oxidoreductase located in the thylakoid membrane. In this work, the energy and charge transfer processes in PSI complexes isolated from Thermosynechococcus elongatus via conventional n-dodecyl-beta-D-maltoside solubilization (DM-PSI) and a, to our knowledge, new detergent-free method using styrene-maleic acid copolymers (SMA-PSI) have been investigated by pump-to-probe femtosecond laser spectroscopy. In DM-PSI preparations excited at 740 nm, the excitation remained localized on the long-wavelength chlorophyll forms within 0.1-20 ps and revealed little or no charge separation and oxidation of the special pair, P700. The formation of ionradical pair P700(+)A1(-) occurred with a characteristic time of 36 ps, being kinetically controlled by energy transfer from the long-wavelength chlorophyll to P-700. Quite surprisingly, the detergent-free SMA-PSI complexes upon excitation by these long-wave pulses undergo an ultrafast (<100 fs) charge separation in similar to 45% of particles. In the remaining complexes (similar to 55%), the energy transfer to P-700 occurred at similar to 36 ps, similar to the DM-PSI. Both isolation methods result in a trimeric form of PSI, yet the SMA-PSI complexes display a heterogenous kinetic behavior. The much faster rate of charge separation suggests the existence of an ultrafast pathway for charge separation in the SMA-PSI that may be disrupted during detergent isolation.
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