Magnetic interaction between QA−. and the triplet state of the primary donor in modified reaction centers of the photosynthetic bacterium Rhodobacter sphaeroides R26

Author(s):
Bosch, M.K.; Gast, P.; Franken, E.M.; Zwanenburg, G.; Hore, P.J.; Hoff, A.J.
Published
1996
Publication type
Article / Letter to editor

Abstract

The interaction between the reduced primary acceptor quinone (Q(A)(-.)), and the triplet state of the primary donor D-3 is investigated with time-resolved continuous-wave EPR, The trough at high-field in the Q(A)(-.) electron-spin polarized X-band EPR-spectrum at early delay times after the laser flash [De Groot et al. (1985) Biochim. Biophys. Acta 808, 13-20] is studied as a function of temperature and of the delay, in zinc-reconstituted reaction centers, with and without carotenoid. In all cases investigated a decrease in D-3 concentration is accompanied by a simultaneous attenuation of the high-field trough in the Q(A)(-.) EPR spectrum. These observations confirm the hypothesis that the line-shape of Q(A)(-.) at short delay times is influenced by a magnetic interaction with D-3. The line-shape of the Q(A)(-.) electron-spin polarized EPR spectrum directly after the laser flash, could be very well simulated using an extension of the model of Hore et al. [Here, P.J. et al. (1993) Biochim. Biophys. Acta 1141, 221-230], with a dipolar coupling between Q(A)(-.) and D-3 Of -0.125 mT.

Date issued
1996-09-12
Language
English
Publisher
ELSEVIER SCIENCE BV
Is part of
Biochimica et Biophysica Acta. Bioenergetics (1996), Vol. 1276, no. 2, p. 106-116
hdl
1887/3590407
doi
10.1016/0005-2728(96)00064-3