15 N photochemically induced dynamic nuclear polarization magic-angle spinning NMR analysis of the electron donor of photosystem II
- 31 July 2007
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 104 (31), 12767-12771
- https://doi.org/10.1073/pnas.0701763104
Abstract
In natural photosynthesis, the two photosystems that operate in series to drive electron transport from water to carbon dioxide are quite similar in structure and function, but operate at widely different potentials. In both systems photochemistry begins by photo-oxidation of a chlorophyll a, but that in photosystem II (PS2) has a 0.7 eV higher midpoint potential than that in photosystem I (PS1), so their electronic structures must be very different. Using reaction centers from (15)N-labeled spinach, these electronic structures are compared by their photochemically induced dynamic nuclear polarization (photo-CIDNP) in magic-angle spinning (MAS) NMR measurements. The results show that the electron spin distribution in PS1, apart from its known delocalization over 2 chlorophyll molecules, reveals no marked disturbance, whereas the pattern of electron spin density distribution in PS2 is inverted in the oxidized radical state. A model for the donor of PS2 is presented explaining the inversion of electron spin density based on a tilt of the axial histidine toward pyrrole ring IV causing pi-pi overlap of both aromatic systems.Keywords
This publication has 39 references indexed in Scilit:
- Signals in Solid-State Photochemically Induced Dynamic Nuclear Polarization Recover Faster Than Signals Obtained with the Longitudinal Relaxation TimeThe Journal of Physical Chemistry B, 2007
- Redox Potentials of Chlorophylls in the Photosystem II Reaction CenterBiochemistry, 2005
- Orientation and Electronic Structure of the Primary Donor Radical Cation in Photosystem I: A Single Crystals EPR and ENDOR StudyThe Journal of Physical Chemistry B, 2001
- Solid State 15N NMR Evidence for a Complex Schiff Base Counterion in the Visual G-Protein-Coupled Receptor RhodopsinBiochemistry, 1999
- A Coherent Mixing Mechanism Explains the Photoinduced Nuclear Polarization in Photosynthetic Reaction CentersThe Journal of Physical Chemistry B, 1998
- A New Mechanism for Chemically Induced Dynamic Nuclear Polarization in the Solid StateJournal of the American Chemical Society, 1998
- Pulsed EPR measurement of the distance between P680+· and QA−· in photosystem IIFEBS Letters, 1997
- Photochemically Induced Dynamic Nuclear Polarization in the Solid-State 15N Spectra of Reaction Centers from Photosynthetic Bacteria Rhodobacter sphaeroides R-26Journal of the American Chemical Society, 1994
- ENDOR and Special Triple Resonance Studies of Chlorophyll Cation Radicals in Photosystem 2Biochemistry, 1994
- Carbon-13 magic angle spinning NMR study of the light-induced and temperature-dependent changes in Rhodobacter sphaeroides R26 reaction centers enriched in [4'-13C]tyrosineBiochemistry, 1992