Electron paramagnetic resonance of the primary radical pair [D·+φA·−] in reaction centers of photosynthetic bacteria

Author(s):
Proskuryakov, I.I.; Klenina, I.B.; Hore, P.J.; Bosch, M.K.; Gast, P.; Hoff, A.J.
Published
1996
Publication type
Article / Letter to editor

Abstract

Using continuous wave EPR spectroscopy with a high time resolution, a new short-lived signal at g = 2 is observed in bacterial photosynthetic reaction centers in which electron transfer past the bacteriopheophytin Phi(A) is blocked. This signal decays with a time constant equal to the rise time of the triplet state of the primary donor D-3, and is therefore attributed to the primary radical pair [D(.+)Phi(A)(.-)]. Applying the theory of spin-correlated radical pairs, the spectrum could be satisfactorily simulated, yielding the following magnetic interaction parameters between D-.t and Phi(A)(.-): exchange interaction J(D Phi) = -0.9 +/- 0.1 mT and J(D Phi) = -1.7 +/- 0.1 mT for reaction centers of Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis, respectively, and an axial dipolar interaction D-D Phi = -3.0 +/- 0.5 mT for Rhodopseudomonas viridis, The implications of We magnitude and sign of the exchange parameters for the energetics of photosynthetic electron transfer are discussed.

Date issued
1996-07-26
Language
English
Publisher
ELSEVIER SCIENCE BV
Is part of
Chemical Physics Letters (1996), Vol. 257, no. 3-4, p. 333-339
hdl
1887/3590164
doi
10.1016/0009-2614(96)00529-5