The g = 4. 1 EPR signal of the S sub 2 state of the photosynthetic oxygen-evolving complex arises from a multinuclear Mn cluster

Journal Article · Wed Dec 05 04:00:00 EST 1990 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00181a049· OSTI ID:5890322

Kim, D H; Sauer, K ^[1]; Britt, R D ^[2]; Klein, M P ^[3]

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1. Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley (United States)
2. Univ. of California, Davis (United States)
3. Lawrence Berkeley Lab., CA (United States)

The process of water oxidation and dioxygen evolution by the photosystem II (PSII) component of plant photosynthesis is cyclic, with intermediate states of the oxygen-evolving complex (OEC) designated S{sub 0} through S{sub 4}. Two electron paramagnetic resonance (EPR) signals have been assigned to the S{sub 2} state of the complex. A multiline' EPR signal centered at the g = 2 region of the spectrum shows 16 or more partially resolved Mn hyperfine transitions and arises from a cluster with a minimum of two exchange-coupled mixed-valence Mn atoms. The other S{sub 2} EPR signal occurs in the g = 4.1 region of the spectrum. The lack of resolved Mn hyperfine couplings has prevented conclusive assignment of the g = 4.1 EPR signal to a Mn center. However, a shift of the Mn X-ray K edge to higher energies is correlated with the appearance of the g = 4.1 signal in PSII membranes illuminated at 140 K. A considerable body of experimental work, including measurements of the temperature dependence of the EPR signals and observations of the interconversion between the multiline and the g = 4.1 signals, has given rise to two different models involving S = 3/2 Mn origins for the g = 4.1 signal. In this communication, the authors present direct spectral evidence of a multinuclear Mn origin for the S{sub 2} g = 4.1 signal.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5890322
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 112:25; ISSN 0002-7863; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
CHEMICAL REACTIONS
COMPLEXES
ELECTRON SPIN RESONANCE
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
MANGANESE COMPLEXES
MOLECULAR STRUCTURE
OXIDATION
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHOTOSYNTHETIC REACTION CENTERS
REACTION INTERMEDIATES
RESONANCE
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
WATER