Low-temperature (77 K) illumination of manganese-depleted Synechocystis PCC 6803 photosystem II core complexes caused the reversible photooxidation of a carotenoid, forming a carotenoid cation radical with an absorbance maximum at 984 nm. Resonance FT-Raman spectra obtained with 1064 nm excitation gave a spectrum characteristic of carotenoid cation radicals in solution. This is the first example of a resonance Raman spectrum of a carotenoid cation radical in a protein. The carotenoid photooxidation requires prior chemical oxidation of cytochrome b559 which implicates the carotenoid in the secondary electron-transfer pathway of photosystem II that may play a role in photoprotection. The possible nature of the pathway and the structure of the carotenoid cation radical are discussed.
|Number of pages||4|
|Journal||Journal of Physical Chemistry B|
|Publication status||Published - Aug 5 1999|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry