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Evidence for the electrochromic identification of the change of charges in the four oxidation steps of the photoinduced water cleavage in photosynthesis
Author(s) -
Saygin Ö.,
Witt H.T.
Publication year - 1985
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(85)81246-1
Subject(s) - electrochromism , photochemistry , chemistry , photosystem ii , proton , photosynthesis , oxygen , absorption band , absorption spectroscopy , analytical chemistry (journal) , electrode , optics , physics , organic chemistry , quantum mechanics , biochemistry
After dark adaptation of oxygen‐evolving photosystem (PS) II complexes, oscillatory absorption changes (stable >0.5 s) with a period of 4 were previously detected at 514 nm, probably due to electrochromic band shifts of carotenoids [(1984) FEBS Lett. 176, 83‐87]. To support this interpretation, we looked for corresponding phenomena in the 650–714 nm range. Here, oscillations were also observed with a difference spectrum giving evidence for an electrochromic band shift of the chlorophyll a absorption band. The oscillation pattern 0:0:+:+ corresponds to those at 514 nm, supporting the former conclusion that the states S 2 and S 3 have a surplus charge compared to S 0 and S 1 . This is possible if the electron release pattern 1:1:1:1 is accompanied by an intrinsic proton release pattern 1:0:1:2 for the transition S 0 → S 1 → S 2 → S 3 → S 0 .