Similarity of EPR Signal IIf rise and P-680+ decay kinetics in Tris-washed chloroplast Photosystem II preparations as a function of pH

Michael Boska, Kenneth Sauer, William Buttner, Gerald T. Babcock

Research output: Contribution to journalArticle

67 Scopus citations


The rise time, of Signal IIf and the decay time of P-680+ have been measured kinetically as a function of pH by using EPR. The Photosystem II-enriched preparations which were used as samples were derived from spinach chloroplasts, and they evolved oxygen before Tris washing. The onset kinetics of Signal IIf are in agreement, within experimental error, with the fast component of the decay of an EPR signal attributable to P-680+. The signal IIf rise kinetics also show good agreement with published values of the pH dependence of the decay of P-680+ measured optically (Conjeaud, H. and Mathis, P. (1980) Biochim. Biophys. Acta 590, 353-359). These results are consistent with a model where the species Z (or D1) responsible for Signal IIf is the immediate electron donor to P-680+ in tris-washed Photosystem II fragments.

Original languageEnglish (US)
Pages (from-to)327-330
Number of pages4
JournalBBA - Bioenergetics
Issue number2
Publication statusPublished - Feb 17 1983



  • (Spinach chloroplast)
  • ESR
  • Electron transfer
  • P-680
  • Photosynthesis
  • Photosystem II

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

Cite this