A comparative electron spin echo envelope modulation study of the primary electron acceptor quinone in Zn-substituted and cyanide-treated preparations of photosystem II

Andrei V. Astashkirn, Hideyuki Hara, Shigeki Kuroiwa, Asako Kawamori, Kozo Akabori

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Abstract

The electron spin echo envelope modulation spectra of the reduced primary acceptor quinone, QA, in two preparations of plant photosystem II, have been studied. In one of these preparations the Fe2+ ion in the quinone-iron complex has been substituted by diamagnetic Zn2+. In the other preparation this iron ion has been converted into the diamagnetic state using a potassium cyanide treatment. A comparative analysis of two-dimensional three-pulse electron spin echo envelope modulation spectra has shown similar structure of the binding site of QA in both preparations. Two nitrogen nuclei have been found to contribute to the spectra in both preparations. One of these nitrogens is, most probably, an amino nitrogen in the imidazole ring of histidine 215 of the D2 protein. The other nitrogen has been assigned to the peptide group of alanine 261 of the D2 protein. The numerical simulations of the electron spin echo envelope modulation spectra have shown that both nitrogens are simultaneously bound to QA.

Original languageEnglish
Pages (from-to)10143-10151
Number of pages9
JournalJournal of Chemical Physics
Volume108
Issue number24
Publication statusPublished - 1998 Jun 22

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ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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