Effects of sodium dodecyl sulfate and methyl viologen on the differential extinction coefficient of P-700 - a band shift of chlorophyll a associated with oxidation of P-700

Kintake Sonoike, Sakae Katoh

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The magnitude of flash-induced bleaching at 700 nm in the thylakoid membranes isolated from the thermophilic cyanobacterium Synechococcus sp. was affected neither by addition of 4 mM methyl viologen, nor by treatment of the membranes with 0.1% sodium dodecyl sulfate (SDS) for 1 h, but appreciably increased on addition of methyl viologen to the SDS-treated membranes. Detailed studies on the light-minus-dark difference spectrum of P-700 revealed that methyl viologen induces a shift-type change consisting of a bleaching at 695 nm and a positive band at 685 nm, and consequently increases the magnitude of the 700 nm bleaching without affecting P-700 photooxidation in the SDS-treated membranes. Other bipyridinium dyes, 1,1′-trimethylene-2,2′-bipyridinium dibromide and 1,1′-trimethylene-5,5′-dimethyl-2,2′-bipyridinium dibromide were equally effective as methyl viologen, and a prolonged treatment of the membranes with SDS caused a similar band shift in the difference spectrum of P-700. The band shift is closely associated with P-700 oxidation because, on redox titration, the magnitude of the band shift varied in parallel to the amount of P-700 oxidized by light. Methyl viologen also induced the band shift in the chemically oxidized-minus-reduced difference spectrum of P-700 in the SDS-treated membranes. Thus, the band shift is not related to reduction of a bound electron acceptor. As a consequence of the band shift, the oxidized-minus-reduced differential extinction coefficient of P-700 in the 700 nm region was increased by 40%. The extinction coefficient was 64 mM-1 · cm-1 at 701 nm in the thylakoid membranes, whereas the 1-h treated membranes with added methyl viologen, or a Photosystem I reaction center complex prepared by SDS-gel electrophoresis, showed the extinction value of 84-86 mM-1 · cm-1 at 698 nm. Two different models for the band shift are discussed.

Original languageEnglish
Pages (from-to)61-71
Number of pages11
JournalBBA - Bioenergetics
Volume935
Issue number1
DOIs
Publication statusPublished - 1988 Aug 17
Externally publishedYes

Keywords

  • (Synechococcus sp.)
  • Electrochromic shift
  • Methyl viologen
  • P-700
  • Photosystem I
  • Sodium dodecyl sulfate

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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