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DIFFERENCE SPECTRA OF THE OXIDIZED INTERMEDIATES IN THE PHOTOSYNTHETIC OXYGEN‐EVOLVING SYSTEM: EVIDENCE FOR A SMALL S 0 →S 1 ABSORPTION CHANGE
Author(s) -
Lavergne Jearome
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb04154.x
Subject(s) - spectral line , absorption (acoustics) , photosynthesis , oxygen , absorption spectroscopy , oxygen evolution , wavelength , chemistry , analytical chemistry (journal) , variance (accounting) , physics , optics , quantum mechanics , environmental chemistry , accounting , business , biochemistry , organic chemistry , electrode , electrochemistry
— A consensus has emerged in the recent literature on the fact that the UV difference spectrum of the first oxidation step (S 0 → S 1 ) of the photosynthetic oxygen‐evolving complex is significantly different and generally smaller than the spectra of the higher oxidation steps (S 0 → S 1 and S 2 → S 3 ). Discrepancies still persist, however, notably in the 300 nm region where the S 0 → S 1 change was either reported to be markedly smaller than the other changes, or, at variance, to have a similar amplitude. A novel approach is proposed here for estimating the ratio of these changes, requiring no estimate of the Kok model parameters, such as the initial S 0 /S 1 ratio, or damping coefficients. This was achieved by comparing the absorption difference between two fully deactivated states, differing only in their S 0 /S 1 , distribution, with the flash‐induced changes measured from these states. The results show that, at two wavelengths around 300 nm, the S 0 → S 1 change is at least 4 times, and probably 5–6 times smaller than the S 0 → S 1 change.