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Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving
Bridgette A Barry1, Ian B Cooper, Antonio De Riso
1School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30032, USA. bridgette.barry@chemistry.gatech.edu
Summary
Photosystem II
Area of Science:
- Biochemistry
- Photosynthesis research
- Molecular biology
Background:
- Photosynthetic oxygen production by photosystem II (PSII) is vital for aerobic life.
- Oxygen evolution occurs at the PSII oxygen-evolving complex (OEC) via a manganese cluster.
- The OEC cycles through five oxidation states (S0-S4) for oxygen release.
Purpose of the Study:
- To investigate the intermediates formed during the S-state transitions in PSII.
- To elucidate the timing and nature of these intermediates in the catalytic cycle.
Main Methods:
- Utilized time-resolved vibrational spectroscopy.
- Analyzed data on the microsecond to millisecond timescale.
- Focused on detecting protein-derived intermediates during S-state transitions.
Main Results:
- Provided evidence for intermediates during each S-state transition.
- Observed these intermediates on the microsecond to millisecond timescale.
- Detected protein-derived intermediates using time-resolved vibrational spectroscopy.
Conclusions:
- Protein-derived conformational changes or proton transfer reactions precede Mn redox reactions.
- These events are critical during the S2-to-S3 and S3-to-S0 transitions.
- Understanding these intermediates refines models of the oxygen-evolving mechanism.