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Relaxation behaviour of the tyrosine Y-D radical in photosystem II: evidence for strong dipolar interaction with paramagnetic centers in the S-1 and S-2 states

Mamedov, Fikret LU ; Smith, P J; Styring, Stenbjörn LU and Pace, R J (2004) In Physical Chemistry Chemical Physics 6(20). p.4890-4896
Abstract
Inversion recovery (T-1) and microwave power saturation studies have been performed, between 4 and 25 K, on the EPR signal from the stable tyrosyl radical, Y-D(.), in photosystem II core complex preparations from higher plants. Measurements are reported from the dark stable S-1 and first turnover S-2 states of the photosystem catalytic Mn cluster and in two cryoprotectant regimes; sucrose and ethylene glycol/glycerol. The inversion recovery kinetics show a dominant, non exponential decay component which is well described by a through space dipolar relaxation model, with a weak exponential decay background (similar toan order of magnitude less than the dipolar rate). The dipolar relaxation rate is only modestly temperature dependent and... (More)
Inversion recovery (T-1) and microwave power saturation studies have been performed, between 4 and 25 K, on the EPR signal from the stable tyrosyl radical, Y-D(.), in photosystem II core complex preparations from higher plants. Measurements are reported from the dark stable S-1 and first turnover S-2 states of the photosystem catalytic Mn cluster and in two cryoprotectant regimes; sucrose and ethylene glycol/glycerol. The inversion recovery kinetics show a dominant, non exponential decay component which is well described by a through space dipolar relaxation model, with a weak exponential decay background (similar toan order of magnitude less than the dipolar rate). The dipolar relaxation rate is only modestly temperature dependent and shows no consistent dependence on S state or cryoprotectant. In contrast, the background rate shows a S state dependence, consistent with an interaction between Y-D(.) and the Mn cluster in the multiline S-2 state, over a distance of similar to30 Angstrom. The fraction of centers exhibiting the dipolar relaxation component appears to be temperature dependent, but S state independent and consistent with the presence of a fast relaxing species interacting with Y-D(.). The present results and the possible nature of this interacting species are discussed in comparison with earlier Y-D(.) relaxation studies on photosystem II membrane samples. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Chemistry Chemical Physics
volume
6
issue
20
pages
4890 - 4896
publisher
Royal Society of Chemistry
external identifiers
  • wos:000224755500023
  • scopus:8144230859
ISSN
1463-9084
DOI
10.1039/b407329k
language
English
LU publication?
yes
id
ad2c55ef-69d4-4e5d-b4bb-e06b3d05d4b9 (old id 138678)
date added to LUP
2007-07-06 11:12:24
date last changed
2017-01-01 06:57:12
@article{ad2c55ef-69d4-4e5d-b4bb-e06b3d05d4b9,
  abstract     = {Inversion recovery (T-1) and microwave power saturation studies have been performed, between 4 and 25 K, on the EPR signal from the stable tyrosyl radical, Y-D(.), in photosystem II core complex preparations from higher plants. Measurements are reported from the dark stable S-1 and first turnover S-2 states of the photosystem catalytic Mn cluster and in two cryoprotectant regimes; sucrose and ethylene glycol/glycerol. The inversion recovery kinetics show a dominant, non exponential decay component which is well described by a through space dipolar relaxation model, with a weak exponential decay background (similar toan order of magnitude less than the dipolar rate). The dipolar relaxation rate is only modestly temperature dependent and shows no consistent dependence on S state or cryoprotectant. In contrast, the background rate shows a S state dependence, consistent with an interaction between Y-D(.) and the Mn cluster in the multiline S-2 state, over a distance of similar to30 Angstrom. The fraction of centers exhibiting the dipolar relaxation component appears to be temperature dependent, but S state independent and consistent with the presence of a fast relaxing species interacting with Y-D(.). The present results and the possible nature of this interacting species are discussed in comparison with earlier Y-D(.) relaxation studies on photosystem II membrane samples.},
  author       = {Mamedov, Fikret and Smith, P J and Styring, Stenbjörn and Pace, R J},
  issn         = {1463-9084},
  language     = {eng},
  number       = {20},
  pages        = {4890--4896},
  publisher    = {Royal Society of Chemistry},
  series       = {Physical Chemistry Chemical Physics},
  title        = {Relaxation behaviour of the tyrosine Y-D radical in photosystem II: evidence for strong dipolar interaction with paramagnetic centers in the S-1 and S-2 states},
  url          = {http://dx.doi.org/10.1039/b407329k},
  volume       = {6},
  year         = {2004},
}