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Electron Spin−Lattice Relaxation Measurement of the 3Fe-4S (S-3) Cluster in Succinate:Ubiquinone Reductase from Paracoccus Denitrificans. A Detailed Analysis Based on a Dipole−Dipole Interaction Model

Hung, Shao-Ching and Grant, Christopher V. and Peloquin, Jeffrey M. and Waldeck, A. Reginald and Britt, R. David and Chan, Sunney I. (2000) Electron Spin−Lattice Relaxation Measurement of the 3Fe-4S (S-3) Cluster in Succinate:Ubiquinone Reductase from Paracoccus Denitrificans. A Detailed Analysis Based on a Dipole−Dipole Interaction Model. Journal of Physical Chemistry A, 104 (19). pp. 4402-4412. ISSN 1089-5639. http://resolver.caltech.edu/CaltechAUTHORS:20170419-092628378

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Abstract

The electron spin−lattice relaxation for the 3Fe-4S (S-3) center in succinate:ubiquinone reductase has been examined using both inversion recovery and “picket-fence” pulse sequences at a temperature range of 4−8 K. The latter pulse sequence is used to eliminate the interference of spectral diffusion in frozen solids. An abnormally fast relaxation was observed for the S-3 center. We attribute this rapid relaxation to a magnetic dipolar interaction between the S-3 center and a nearby paramagnetic b-heme (cytochrome b). A model has been developed to treat the interaction between two paramagnetic redox centers in a rigid lattice at a fixed distance apart but with random orientations in a magnetic field. Both the contribution to the spin−lattice relaxation rate from the dipolar interaction (k_(1θ)), which is anisotropic, and the intrinsic electron spin relaxation, which is scalar (k_(1scalar)), have been deduced. We find that the contribution of exchange interaction to the anisotropic part of the relaxation rate (k1θ) is very small. Accordingly, we conclude that k_(1scalar) is dominated by the intrinsic electron spin−lattice relaxation. From k_(1θ), a lower limit (r > 10 Å) has been deduced for the distance between the S-3 center and the b-heme.


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http://dx.doi.org/10.1021/jp993693iDOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp993693iPublisherArticle
ORCID:
AuthorORCID
Chan, Sunney I.0000-0002-5348-2723
Additional Information:© 2000 American Chemical Society. Received: October 18, 1999; In Final Form: January 20, 2000. Publication Date (Web): April 4, 2000. We thank Dr. Brian E. Schultz and Professor Gary W. Brudvig for numerous discussion on this work. This work was supported by the NIH grants GM22432 (to S.I.C.) and GM48242 (to R.D.B.) from the U.S. Public Health Service.
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Funding AgencyGrant Number
NIHGM22432
NIHGM48242
Record Number:CaltechAUTHORS:20170419-092628378
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170419-092628378
Official Citation:Electron Spin−Lattice Relaxation Measurement of the 3Fe-4S (S-3) Cluster in Succinate:Ubiquinone Reductase from Paracoccus Denitrificans. A Detailed Analysis Based on a Dipole−Dipole Interaction Model Shao-Ching Hung, Christopher V. Grant, Jeffrey M. Peloquin, A. Reginald Waldeck, R. David Britt, and Sunney I. Chan The Journal of Physical Chemistry A 2000 104 (19), 4402-4412 DOI: 10.1021/jp993693i
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76665
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:19 Apr 2017 16:33
Last Modified:22 Sep 2017 04:44

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