Light-induced Fourier transform infrared spectrum of the cation radical P680+

S. I. Allakhverdiev, A. Ahmed, H. A. Tajmir-Riahi, V. V. Klimov, R. Carpentier

    Research output: Contribution to journalArticlepeer-review


    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.

    Original languageEnglish
    Pages (from-to)151-154
    Number of pages4
    JournalFEBS Letters
    Issue number1-2
    Publication statusPublished - Feb 14 1994


    • Chlorophyll
    • Fourier transform infrared spectroscopy
    • P680
    • Photosynthesis
    • Photosystem II

    ASJC Scopus subject areas

    • Biophysics
    • Structural Biology
    • Biochemistry
    • Molecular Biology
    • Genetics
    • Cell Biology


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