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Metalloradical EPR signals from the YZ·S-State intermediates in photosystem II

Havelius, Kajsa G.V. LU ; Sjöholm, Johannes ; Ho, Felix M. ; Mamedov, Fikret LU and Styring, Stenbjörn LU (2010) In Applied Magnetic Resonance 37(1). p.151-176
Abstract

The redox-active tyrosine residue (YZ) plays a crucial role in the mechanism of the water oxidation. Metalloradical electron paramagnetic resonance (EPR) signals reflecting the light-induced YZ· in magnetic interaction with the CaMn4-cluster in the particular S-state, YZ·SX intermediates, have been found in intact photosystem II. These so-called split EPR signals are induced by illumination at cryogenic temperatures and provide means to both study the otherwise transient YZ· and to probe the S-states with EPR spectroscopy. The illumination used for signal induction grouped the observed split EPR signals in two categories: (i) YZ in the lower S-states was... (More)

The redox-active tyrosine residue (YZ) plays a crucial role in the mechanism of the water oxidation. Metalloradical electron paramagnetic resonance (EPR) signals reflecting the light-induced YZ· in magnetic interaction with the CaMn4-cluster in the particular S-state, YZ·SX intermediates, have been found in intact photosystem II. These so-called split EPR signals are induced by illumination at cryogenic temperatures and provide means to both study the otherwise transient YZ· and to probe the S-states with EPR spectroscopy. The illumination used for signal induction grouped the observed split EPR signals in two categories: (i) YZ in the lower S-states was oxidized by P680+ formed via charge separation, while (ii) YZ in the higher S-states was oxidized by an excited, highly oxidizing Mn species. Applied mechanistic studies of the YZ·SX intermediates in the different S-states are reviewed and compared to investigations in photosystem II at physiological temperature. Addition of methanol induced S-state characteristic changes in the split signals' formation which reflect changes in the magnetic coupling within the CaMn4-cluster due to methanol binding. The pH titration of the split EPR signals, on the other hand, could probe the proton-coupled electron transfer properties of the YZ oxidation. The apparent pKas found for decreased split signal induction were interpreted in the fate of the phenol proton.

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publishing date
type
Contribution to journal
publication status
published
in
Applied Magnetic Resonance
volume
37
issue
1
pages
26 pages
publisher
Springer
external identifiers
  • scopus:71149115464
ISSN
0937-9347
DOI
10.1007/s00723-009-0045-z
language
English
LU publication?
no
id
733a1015-ff52-41a3-a407-0ec0e70dad21
date added to LUP
2020-01-15 10:29:54
date last changed
2022-02-16 02:11:17
@article{733a1015-ff52-41a3-a407-0ec0e70dad21,
  abstract     = {{<p>The redox-active tyrosine residue (Y<sub>Z</sub>) plays a crucial role in the mechanism of the water oxidation. Metalloradical electron paramagnetic resonance (EPR) signals reflecting the light-induced Y<sub>Z</sub>· in magnetic interaction with the CaMn<sub>4</sub>-cluster in the particular S-state, Y<sub>Z</sub>·S<sub>X</sub> intermediates, have been found in intact photosystem II. These so-called split EPR signals are induced by illumination at cryogenic temperatures and provide means to both study the otherwise transient Y<sub>Z</sub>· and to probe the S-states with EPR spectroscopy. The illumination used for signal induction grouped the observed split EPR signals in two categories: (i) Y<sub>Z</sub> in the lower S-states was oxidized by P680<sup>+</sup> formed via charge separation, while (ii) Y<sub>Z</sub> in the higher S-states was oxidized by an excited, highly oxidizing Mn species. Applied mechanistic studies of the Y<sub>Z</sub>·S<sub>X</sub> intermediates in the different S-states are reviewed and compared to investigations in photosystem II at physiological temperature. Addition of methanol induced S-state characteristic changes in the split signals' formation which reflect changes in the magnetic coupling within the CaMn<sub>4</sub>-cluster due to methanol binding. The pH titration of the split EPR signals, on the other hand, could probe the proton-coupled electron transfer properties of the Y<sub>Z</sub> oxidation. The apparent pK<sub>a</sub>s found for decreased split signal induction were interpreted in the fate of the phenol proton.</p>}},
  author       = {{Havelius, Kajsa G.V. and Sjöholm, Johannes and Ho, Felix M. and Mamedov, Fikret and Styring, Stenbjörn}},
  issn         = {{0937-9347}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{1}},
  pages        = {{151--176}},
  publisher    = {{Springer}},
  series       = {{Applied Magnetic Resonance}},
  title        = {{Metalloradical EPR signals from the Y<sub>Z</sub>·S-State intermediates in photosystem II}},
  url          = {{http://dx.doi.org/10.1007/s00723-009-0045-z}},
  doi          = {{10.1007/s00723-009-0045-z}},
  volume       = {{37}},
  year         = {{2010}},
}