Metalloradical EPR signals from the YZ·S-State intermediates in photosystem II
(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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- author
- Havelius, Kajsa G.V. LU ; Sjöholm, Johannes ; Ho, Felix M. ; Mamedov, Fikret LU and Styring, Stenbjörn LU
- organization
- publishing date
- 2010-01-01
- 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}}, }