Oxygen-Evolution Patterns from Spinach Photosystem II Preparations

Michael Seibert, Jean Lavorel

Research output: Contribution to journalArticlepeer-review

32 Scopus Citations


Patterns of O2 evolution resulting from sequences of short flashes are reported for Photosystem (PS) II preparations isolated from spinach and containing an active, O2-evolving system. The results can be interpreted in terms of the S-state model developed to explain the process of photosynthetic water splitting in chloroplasts and algae. The PS II samples display damped, oscillating patterns of O2 evolution with a period of four flashes. Unlike chloroplasts, the flash yields of the preparations decay with increasing flash number due to the limited plastoquinone acceptor pool on the reducing side of PS II. The optimal pH for O2 evolution in this system (pH 5.5-6.5) is more acidic than in chloroplasts (pH 6.5-8.0). The O2-evolution, inactivation half-time of dark-adapted preparations was 91 min (on the rate electrode) at room temperature. Dark-inactivation half-times of 14 h were observed if the samples were aged off the electrode at room temperature. Under our conditions (experimental conditions can influence flash-sequence results), deactivation of S3 was first order with a half-time of 105 s while that of S2 was biphasic. The half-times for the first-order rapid phase were 17 s (one preflash) and 23 s (two preflashes). The longer S2 phase deactivated very slowly (the minimum half-time observed was 265 s). These results indicate that deactivation from S3 → S2 → S1, thought to be the dominant pathway in chloroplasts, is not the case for PS II preparations. Finally, it was demonstrated that the ratio of S1 to S0 can be set by previously developed techniques, that S0 is formed mostly from activated S3 (S4), and that both S0 and S1 are stable in the dark.

Original languageAmerican English
Pages (from-to)160-168
Number of pages9
JournalBBA - Bioenergetics
Issue number2
StatePublished - 1983
Externally publishedYes

NREL Publication Number

  • ACNR/JA-233-4763


  • (Spinach chloroplast)
  • Oxygen evolution
  • Photosystem II
  • Water splitting


Dive into the research topics of 'Oxygen-Evolution Patterns from Spinach Photosystem II Preparations'. Together they form a unique fingerprint.

Cite this