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Light‐induced Fourier transform infrared spectrum of the cation radical P680 +
Author(s) -
Allakhverdiev S.I.,
Ahmed A.,
Tajmir-Riahi H.-A.,
Klimov V.V.,
Carpentier R.
Publication year - 1994
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(94)80404-4
Subject(s) - p680 , dimer , chemistry , fourier transform infrared spectroscopy , absorbance , photochemistry , photosystem ii , infrared , infrared spectroscopy , analytical chemistry (journal) , photosystem i , photosynthesis , physics , optics , organic chemistry , biochemistry , chromatography
The structure of the primary electron donor of photosystem II, P680, is still under debate. It is not decided if it is composed of a chlorophyll (Chl) monomer or dimer. In this study, Fourier transform infrared (FTIR) spectroscopy was used to analyze the changes in the vibration modes occurring upon photooxidation of P680 in a Mn‐depleted PS II preparation. It is demonstrated that illumination of the above in the presence of artificial electron acceptors results in a light‐minus‐dark absorbance change typical of the formation ofP680 + . The light‐minus‐dark difference FTIR spectrum obtained under similar conditions is characterized by two negative peaks located at 1694 and 1652 or 1626 cm −1 that can be assigned to the 9‐keto groups of the P680 Chl, the latter band being indicative of a strongly associated group. These vibrations are shifted to 1714 and 1676 cm −1 , respectively, in the positive features of the difference spectrum attributed to P680 + . The occurrence of two pairs of bands attributed to 9‐keto groups is discussed in terms of P680 being formed of a Chl dimer.