Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

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)
Please use this url to cite or link to this publication:
author
; ; and
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
2016-04-01 16:09:10
date last changed
2022-01-28 17:39:09
@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}},
  doi          = {{10.1039/b407329k}},
  volume       = {{6}},
  year         = {{2004}},
}