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Shopes RJ, Levine LM, Holten D, et al. Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis. Photosynth Res. 1987;12(2):165-80doi: 10.1007/BF00047946.
Shopes, R. J., Levine, L. M., Holten, D., & Wraight, C. A. (1987). Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis. Photosynthesis research, 12(2), 165-80. https://doi.org/10.1007/BF00047946
Shopes, R J, et al. "Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis." Photosynthesis research vol. 12,2 (1987): 165-80. doi: https://doi.org/10.1007/BF00047946
Shopes RJ, Levine LM, Holten D, Wraight CA. Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis. Photosynth Res. 1987 Jan;12(2):165-80. doi: 10.1007/BF00047946. PMID: 24435639.
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Photosynth Res. 1987 Jan;12(2):165-80. doi: 10.1007/BF00047946.

Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis.

Photosynthesis research

R J Shopes, L M Levine, D Holten, C A Wraight

Affiliations

  1. Department of Physiology and Biophysics, University of Illinois, 61801, Urbana, IL, USA.

PMID: 24435639 DOI: 10.1007/BF00047946

Abstract

The initial oxidized species in the photochemical charge separation in reaction centers from Rps. viridis is the primary donor, P(+), a bacteriochlorophyll dimer. Bound c-type cytochromes, two high potential (Cyt c 558) and two low potential (Cyt c 553), act as secondary electron donors to P(+). Flash induced absorption changes were measured at moderate redox potential, when the high potential cytochromes were chemically reduced. A fast absorption change was due to the initial oxidation of one of the Cyt c 558 by P(+) with a rate of 3.7×10(6)s(-1) (τ=270nsec). A slower absorption change was attributable to a transfer, or sharing, of the remaining electron from one high potential heme to the other, with a rate of 2.8×10(5)s(-1) (τ=3.5 μsec). The slow change was measured at a number of wavelengths throughout the visible and near infrared and revealed that the two high potential cytochromes have slightly different differential absorption spectra, with α-band maxima at 559 nm (Cyt c 559) and 556.5 nm (Cyt c 556), and dissimilar electrochromic effects on nearby pigments. The sequence of electron transfers, following a flash, is: Cyt c 556→Cyt c 559→P(+). At lower redox potentials, a low midpoint potential cytochrome, Cyt c 553, is preferentially oxidized by P(+) with a rate of 7×10(6)s(-1) (τ=140 nsec). The assignment of the low and high potential cytochromes to the four, linearly arranged hemes of the reaction center is discussed. It is concluded that the closest heme to P must be the high potential Cyt c 559, and it is suggested that a likely arrangement for the four hemes is: c 553 c 556 c 553 c 559P.

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