The primary acceptor quinone QA in reaction centers of Rhodobacter sphaeroides R26 is hydrogen bonded to the Nσ(1)-H of His M219. An electron spin echo study of QA−•

Bosch, M.K.; Gast, P.; Hoff, A.J.; Spoyalov, A.P.; Tsvetkov Yu.D. (1995)

Article / Letter to editor

An electron spin echo envelope modulation (ESEEM) study is performed on the reduced primary electron-accepting ubiquinone-10 (Q(A)(-.)) in Zn-substituted reaction centers of the photosynthetic bacterium Rhodobacter sphaeroides R26. The ESEEM spectra showed hyperfine and quadrupolar couplings of Q(A)(-.) to nitrogens in the protein matrix. Simulation of the spectra revealed the following N-14 coupling parameters: hyperfine interaction: A(iso)=1.85 MHz, T-11=0.32, alpha=0(0), beta=45(0); nuclear quadrupole interaction: e(2)qQ/h=1.52 MHz, eta=0.82. Comparison of the quadrupole values with data in the literature shows that Q(A)(-.) is coupled to the N-delta(1)-H group of the M219 heterocycle, most probably through a hydrogen bond with the 4-C carbonyl group of the quinone.

• All authors: Bosch, M.K.; Gast, P.; Hoff, A.J.; Spoyalov, A.P.; Tsvetkov Yu.D.
• Date: 1995-06-16
• Journal: Chemical Physics Letters
• Volume: 239
• Issue: 4-6
• Pages: 306 - 312
• DOI: doi:10.1016/0009-2614(95)00481-I
• Link: https://www.sciencedirect.com/science/article/pii/000926149500481I?via%3...