Thermoluminescence study of charge recombination in Photosystem II at low temperatures. I. Characterization of the Zv and A thermoluminescence bands

S. Demeter, Zs Rozsa, I. Vass, A. Sallai

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Abstract

The characteristics of the Zv and A thermoluminescence bands appearing in the glow curve at about -75 and -30°C, respectively, were investigated in spinach chloroplasts. Inhibitory concentrations of DCMU decreased the amplitude of the Zv band by half and completely abolished the A band. On the other hand, after two preflashes at +2°C before freezing, the A band could be charged by low-temperature illumination even when the electron transport was interrupted between QA and QB by DCMU addition after the preflashes. Two-flash preillumination greatly enhanced the amplitude of the A band, but diminished that of the Zv band. Tris washing and NH2OH treatment, which inactivated the oxygen-evolving system, almost completely abolished the Zv band, but did not affect the A band. Severe trypsin treatment, which also impaired the oxygen-evolving system, resulted in a very large intensification of the Zv band. The half-times of the A and Zv bands, determined by theoretical analysis of the thermoluminescence data, proved to be about 4 ms and 200-500 μs, respectively. These results, taken together with EPR data from the literature, suggest that the A band arises from charge recombination between a negatively charged acceptor located before the DCMU block (most probably Q- A) and the oxidized donor Z+ (which accounts for the EPR Signal IIvf and Signal IIf). The electron carrier responsible for the Zv band is also a component located prior to the inhibitory site of DCMU (Q- A); its interacting counterpart is an unidentified donor which is involved in charge exchange with the S states.

Original languageEnglish
Pages (from-to)369-378
Number of pages10
JournalBBA - Bioenergetics
Volume809
Issue number3
DOIs
Publication statusPublished - Oct 9 1985

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Keywords

  • (Spinach chloroplast)
  • Electron transport
  • Oxygen evolution
  • Photosystem II
  • Thermoluminescence
  • Trypsin

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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