Structure and function of the manganese complex involved in photosynthetic oxygen evolution determined by x-ray adsorption spectroscopy and electron paramagnetic resonance spectroscopy

Technical Report · Fri Apr 01 04:00:00 EST 1988

OSTI ID:7243487

Guiles, R D

Water is the terminal electron donor in the linear light-driven electron transport chain used by higher plants, cyanobacteria and green algae to fix carbon dioxide. The involvement of a membrane-bound manganese-containing protein complex has been demonstrated at the site of water oxidation within the photosystem II (PSII) reaction center. The photosynthetic oxidation of water to molecular oxygen is believed to involve intermediate S-states (S/sub 0//hor ellipsis/S/sub 4/), of the oxygen evolving complex (OEC). The use of multiline EPR signal associated with Mn and assigned to the S/sub 2/ state has greatly facilitated structural characterization of the OEC. This thesis contains a description of methods used to cryogenically stabilize PSII preparations suitable for x-ray absorption spectroscopy in the S/sub 1/, S/sub 2/ and S/sub 3/ states as well as a state induced by hydroxylamine resembling the S/sub 0/ state of the OEC. Studies of the Mn K-edges of PSII preparations indicate that a light-induced oxidation of Mn occurring during the S/sub 1/ ..-->.. S/sub 2/ state transition corresponds to a formal valence change from Mn(III) to Mn(IV). An analysis of the extended x-ray absorption fine structure (EXAFS) of the Mn complex within PSII preparations poised in the S/sub 1/, S/sub 2/, S/sub 3/ and hydroxylamine-induced S/sub 0/ states indicates that the four manganese present are organized as two di-..mu..-oxo bridged binuclear managanese complexes. An essential component of the analysis of the EXAFS was a parallel analysis of a set of crystallographically characterized multinuclear ..mu..-oxo bridged manganese complexes. Based on conclusions drawn from the analysis of the Mn K-edge and EXAFS of PSII preparations cryogenically stabilized in the S-states described above, a model for the mechanism of photosynthetic water oxidation is presented. 274 refs., 46 figs., 17 tabs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 7243487
• Report Number(s): LBL-25186; ON: DE88010360
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
550200 -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
COMPLEXES
ELECTRON SPECTROSCOPY
FOURIER TRANSFORMATION
INTEGRAL TRANSFORMATIONS
MANGANESE COMPLEXES
MEMBRANE PROTEINS
ORGANIC COMPOUNDS
PHOTOSYNTHETIC REACTION CENTERS
PROTEINS
SPECTROSCOPY
THYLAKOID MEMBRANE PROTEINS
TRANSFORMATIONS
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY