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The S0 State EPR Signal from the Mn Cluster in Photosystem II Arises from an Isolated S = 1/2 Ground State

Åhrling, Karin A; Peterson Årsköld, Sindra LU and Styring, Stenbjörn LU (1998) In Biochemistry 37(22). p.8115-8120
Abstract
During oxygen evolution, the Mn cluster in Photosystem II cycles through five oxidation states, S0-S4. S0 and S2 are paramagnetic, and can be monitored by electron paramagnetic resonance (EPR). Recently a new EPR signal from the S0 state was discovered [Åhrling et al. (1997) Biochemistry 36, 13148-13152, Messinger et al. (1997) J. Am. Chem. Soc. 119, 11349-11350]. Here, we present a well-resolved S0 spectrum, taken at high power and low temperature. The spectrum is wider and more resolved than previously thought, with structure over more than 2500 G, and appears to have at least 20 reproducible peaks on each side of g = 2. We also present the temperature dependence of the unsaturated S0 signal amplitude. A linear relationship was found... (More)
During oxygen evolution, the Mn cluster in Photosystem II cycles through five oxidation states, S0-S4. S0 and S2 are paramagnetic, and can be monitored by electron paramagnetic resonance (EPR). Recently a new EPR signal from the S0 state was discovered [Åhrling et al. (1997) Biochemistry 36, 13148-13152, Messinger et al. (1997) J. Am. Chem. Soc. 119, 11349-11350]. Here, we present a well-resolved S0 spectrum, taken at high power and low temperature. The spectrum is wider and more resolved than previously thought, with structure over more than 2500 G, and appears to have at least 20 reproducible peaks on each side of g = 2. We also present the temperature dependence of the unsaturated S0 signal amplitude. A linear relationship was found between signal intensity and reciprocal temperature (1/T) in the region 5-25 K, clearly extrapolating to 0. This obeys the Curie law, indicating that the S0 state is a ground S = 1/2 state with no thermally accessible excited state. The data are consistent with a minimum energy gap of 30 cm-1 between the ground and first excited states. (Less)
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organization
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Contribution to journal
publication status
published
subject
in
Biochemistry
volume
37
issue
22
pages
8115 - 8120
publisher
The American Chemical Society
ISSN
0006-2960
language
English
LU publication?
yes
id
ceb21bc7-5879-4f1c-8579-f91f86752838 (old id 125633)
alternative location
http://pubs.acs.org/cgi-bin/abstract.cgi/bichaw/1998/37/i22/abs/bi980117o.html
date added to LUP
2007-07-06 17:00:27
date last changed
2016-04-15 20:26:41
@article{ceb21bc7-5879-4f1c-8579-f91f86752838,
  abstract     = {During oxygen evolution, the Mn cluster in Photosystem II cycles through five oxidation states, S0-S4. S0 and S2 are paramagnetic, and can be monitored by electron paramagnetic resonance (EPR). Recently a new EPR signal from the S0 state was discovered [Åhrling et al. (1997) Biochemistry 36, 13148-13152, Messinger et al. (1997) J. Am. Chem. Soc. 119, 11349-11350]. Here, we present a well-resolved S0 spectrum, taken at high power and low temperature. The spectrum is wider and more resolved than previously thought, with structure over more than 2500 G, and appears to have at least 20 reproducible peaks on each side of g = 2. We also present the temperature dependence of the unsaturated S0 signal amplitude. A linear relationship was found between signal intensity and reciprocal temperature (1/T) in the region 5-25 K, clearly extrapolating to 0. This obeys the Curie law, indicating that the S0 state is a ground S = 1/2 state with no thermally accessible excited state. The data are consistent with a minimum energy gap of 30 cm-1 between the ground and first excited states.},
  author       = {Åhrling, Karin A and Peterson Årsköld, Sindra and Styring, Stenbjörn},
  issn         = {0006-2960},
  language     = {eng},
  number       = {22},
  pages        = {8115--8120},
  publisher    = {The American Chemical Society},
  series       = {Biochemistry},
  title        = {The S0 State EPR Signal from the Mn Cluster in Photosystem II Arises from an Isolated S = 1/2 Ground State},
  volume       = {37},
  year         = {1998},
}