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Title: Structural changes correlated with magnetic spin state isomorphism in the S 2 state of the Mn 4CaO 5 cluster in the oxygen-evolving complex of photosystem II

The Mn 4CaO 5 cluster in photosystem II catalyzes the four-electron redox reaction of water oxidation in natural photosynthesis. This catalytic reaction cycles through four intermediate states (S i, i = 0 to 4), involving changes in the redox state of the four Mn atoms in the cluster. Recent studies suggest the presence and importance of isomorphous structures within the same redox/intermediate S-state. It is highly likely that geometric and electronic structural flexibility play a role in the catalytic mechanism. Among the catalytic intermediates that have been identified experimentally thus far, there is clear evidence of such isomorphism in the S2 state, with a high-spin (5/2) (HS) and a low spin (1/2) (LS) form, identified and characterized by their distinct electron paramagnetic resonance (EPR spectroscopy) signals. We studied these two S2 isomers with Mn extended X-ray absorption fine structure (EXAFS) and absorption and emission spectroscopy (XANES/XES) to characterize the structural and electronic structural properties. The geometric and electronic structure of the HS and LS S2 states are different as determined using Mn EXAFS and XANES/XES, respectively. The Mn K-edge XANES and XES for the HS form are different from the LS and indicate a slightly lower positive charge on themore » Mn atoms compared to the LS form. Based on the EXAFS results which are clearly different, we propose possible structural differences between the two spin states. As a result, such structural and magnetic redox-isomers if present at room temperature, will likely play a role in the mechanism for water-exchange/oxidation in photosynthesis.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [4] ;  [4] ;  [4] ;  [4] ;  [5] ;  [1] ;  [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Center for High Pressure Science & Technology Advanced Research, Shanghai (China)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  5. RIKEN, Research Cluster for Innovation, Saitama (Japan)
Publication Date:
Grant/Contract Number:
AC02-76SF00515; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 7; Journal Issue: 8; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1312791
Alternate Identifier(s):
OSTI ID: 1379222

Chatterjee, Ruchira, Han, Guangye, Kern, Jan, Gul, Sheraz, Fuller, Franklin D., Garachtchenko, Anna, Young, Iris D., Weng, Tsu -Chien, Nordlund, Dennis, Alonso-Mori, Roberto, Bergmann, Uwe, Sokaras, Dimosthenis, Hatakeyama, Makoto, Yachandra, Vittal K., and Yano, Junko. Structural changes correlated with magnetic spin state isomorphism in the S2 state of the Mn4CaO5 cluster in the oxygen-evolving complex of photosystem II. United States: N. p., Web. doi:10.1039/c6sc00512h.
Chatterjee, Ruchira, Han, Guangye, Kern, Jan, Gul, Sheraz, Fuller, Franklin D., Garachtchenko, Anna, Young, Iris D., Weng, Tsu -Chien, Nordlund, Dennis, Alonso-Mori, Roberto, Bergmann, Uwe, Sokaras, Dimosthenis, Hatakeyama, Makoto, Yachandra, Vittal K., & Yano, Junko. Structural changes correlated with magnetic spin state isomorphism in the S2 state of the Mn4CaO5 cluster in the oxygen-evolving complex of photosystem II. United States. doi:10.1039/c6sc00512h.
Chatterjee, Ruchira, Han, Guangye, Kern, Jan, Gul, Sheraz, Fuller, Franklin D., Garachtchenko, Anna, Young, Iris D., Weng, Tsu -Chien, Nordlund, Dennis, Alonso-Mori, Roberto, Bergmann, Uwe, Sokaras, Dimosthenis, Hatakeyama, Makoto, Yachandra, Vittal K., and Yano, Junko. 2016. "Structural changes correlated with magnetic spin state isomorphism in the S2 state of the Mn4CaO5 cluster in the oxygen-evolving complex of photosystem II". United States. doi:10.1039/c6sc00512h. https://www.osti.gov/servlets/purl/1312791.
@article{osti_1312791,
title = {Structural changes correlated with magnetic spin state isomorphism in the S2 state of the Mn4CaO5 cluster in the oxygen-evolving complex of photosystem II},
author = {Chatterjee, Ruchira and Han, Guangye and Kern, Jan and Gul, Sheraz and Fuller, Franklin D. and Garachtchenko, Anna and Young, Iris D. and Weng, Tsu -Chien and Nordlund, Dennis and Alonso-Mori, Roberto and Bergmann, Uwe and Sokaras, Dimosthenis and Hatakeyama, Makoto and Yachandra, Vittal K. and Yano, Junko},
abstractNote = {The Mn4CaO5 cluster in photosystem II catalyzes the four-electron redox reaction of water oxidation in natural photosynthesis. This catalytic reaction cycles through four intermediate states (Si, i = 0 to 4), involving changes in the redox state of the four Mn atoms in the cluster. Recent studies suggest the presence and importance of isomorphous structures within the same redox/intermediate S-state. It is highly likely that geometric and electronic structural flexibility play a role in the catalytic mechanism. Among the catalytic intermediates that have been identified experimentally thus far, there is clear evidence of such isomorphism in the S2 state, with a high-spin (5/2) (HS) and a low spin (1/2) (LS) form, identified and characterized by their distinct electron paramagnetic resonance (EPR spectroscopy) signals. We studied these two S2 isomers with Mn extended X-ray absorption fine structure (EXAFS) and absorption and emission spectroscopy (XANES/XES) to characterize the structural and electronic structural properties. The geometric and electronic structure of the HS and LS S2 states are different as determined using Mn EXAFS and XANES/XES, respectively. The Mn K-edge XANES and XES for the HS form are different from the LS and indicate a slightly lower positive charge on the Mn atoms compared to the LS form. Based on the EXAFS results which are clearly different, we propose possible structural differences between the two spin states. As a result, such structural and magnetic redox-isomers if present at room temperature, will likely play a role in the mechanism for water-exchange/oxidation in photosynthesis.},
doi = {10.1039/c6sc00512h},
journal = {Chemical Science},
number = 8,
volume = 7,
place = {United States},
year = {2016},
month = {5}
}