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Flash photolysis ESR study of photosystem II signal II/sub vf/, the physiological donor to P-680/sup +/

Abstract

In flash-illuminated, oxygen-evolving spinach chloroplasts and green algae, a free radical transient has been observed with spectral parameters similar to those of Signal II (g approx. = 2.0045, ..delta..H/sub pp/ approx. = 19 G). However, in contrast with ESR Signal II, the transient radical does not readily saturate even at microwave power levels of 200 mW. This species is formed most efficiently with ''red'' illumination (lambda < 680 nm) and occurs stoichiometrically in a 1:1 ratio with P-700/sup +/. The Photosystem II transient is formed in less than 100 ..mu..s and decays via first-order kinetics with a halftime of 400-900 ..mu..s. Additionally, the t/sub /sup 1///sub 2// for radical decay is temperature independent between 20 and 4/sup 0/C; however, below 4/sup 0/C the transient signal exhibits Arrhenius behavior with an activation energy of approx. 10 kcal . mol/sup -1/. Inhibition of electron transport through Photosystem II by o-phenanthroline, 3-(3,4-dichlorophenyl)-1,1-dimethylurea or reduced 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone suppresses the formation of the light-induced transient. At low concentrations (0.2 mM), 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone partially inhibits the free radical formation, however, the decay kinetics are unaltered. High concentrations of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (1-5 mM) restore both the transient signal and electron flow through Photosystem II. These findings suggest that this ''quinoidal''  More>>
Authors:
Warden, J T; [1]  Blankenship, R E; Sauer, K
  1. Rensselaer Polytechnic Inst., Troy, NY
Publication Date:
Jan 01, 1976
Product Type:
Journal Article
Reference Number:
ERA-02-052654; EDB-77-114273
Resource Relation:
Journal Name: Biochim. Biophys. Acta; (Netherlands); Journal Volume: 423
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALGAE; PHOTOLYSIS; CHLOROPLASTS; PHOTOSYNTHESIS; CHEMICAL REACTION KINETICS; ELECTRON SPIN RESONANCE; ELECTRON TRANSFER; RADICALS; TRANSIENTS; BIOMASS; CELL CONSTITUENTS; CHEMICAL REACTIONS; DECOMPOSITION; ENERGY SOURCES; KINETICS; MAGNETIC RESONANCE; PHOTOCHEMICAL REACTIONS; PLANTS; REACTION KINETICS; RENEWABLE ENERGY SOURCES; RESONANCE; SYNTHESIS; 400500* - Photochemistry
OSTI ID:
7211146
Country of Origin:
Netherlands
Language:
English
Other Identifying Numbers:
Journal ID: CODEN: BBACA
Submitting Site:
TIC
Size:
Pages: 462-478
Announcement Date:

Citation Formats

Warden, J T, Blankenship, R E, and Sauer, K. Flash photolysis ESR study of photosystem II signal II/sub vf/, the physiological donor to P-680/sup +/. Netherlands: N. p., 1976. Web. doi:10.1016/0005-2728(76)90201-2.
Warden, J T, Blankenship, R E, & Sauer, K. Flash photolysis ESR study of photosystem II signal II/sub vf/, the physiological donor to P-680/sup +/. Netherlands. doi:10.1016/0005-2728(76)90201-2.
Warden, J T, Blankenship, R E, and Sauer, K. 1976. "Flash photolysis ESR study of photosystem II signal II/sub vf/, the physiological donor to P-680/sup +/." Netherlands. doi:10.1016/0005-2728(76)90201-2. https://www.osti.gov/servlets/purl/10.1016/0005-2728(76)90201-2.
@misc{etde_7211146,
title = {Flash photolysis ESR study of photosystem II signal II/sub vf/, the physiological donor to P-680/sup +/}
author = {Warden, J T, Blankenship, R E, and Sauer, K}
abstractNote = {In flash-illuminated, oxygen-evolving spinach chloroplasts and green algae, a free radical transient has been observed with spectral parameters similar to those of Signal II (g approx. = 2.0045, ..delta..H/sub pp/ approx. = 19 G). However, in contrast with ESR Signal II, the transient radical does not readily saturate even at microwave power levels of 200 mW. This species is formed most efficiently with ''red'' illumination (lambda < 680 nm) and occurs stoichiometrically in a 1:1 ratio with P-700/sup +/. The Photosystem II transient is formed in less than 100 ..mu..s and decays via first-order kinetics with a halftime of 400-900 ..mu..s. Additionally, the t/sub /sup 1///sub 2// for radical decay is temperature independent between 20 and 4/sup 0/C; however, below 4/sup 0/C the transient signal exhibits Arrhenius behavior with an activation energy of approx. 10 kcal . mol/sup -1/. Inhibition of electron transport through Photosystem II by o-phenanthroline, 3-(3,4-dichlorophenyl)-1,1-dimethylurea or reduced 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone suppresses the formation of the light-induced transient. At low concentrations (0.2 mM), 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone partially inhibits the free radical formation, however, the decay kinetics are unaltered. High concentrations of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (1-5 mM) restore both the transient signal and electron flow through Photosystem II. These findings suggest that this ''quinoidal'' type ESR transient functions as the physiological donor to the oxidized reaction center chlorophyll, P-680/sup +/.}
doi = {10.1016/0005-2728(76)90201-2}
journal = {Biochim. Biophys. Acta; (Netherlands)}
volume = {423}
journal type = {AC}
place = {Netherlands}
year = {1976}
month = {Jan}
}