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

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9 Citations (Scopus)


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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