Photochemical reaction centers from Rhodopseudomonas spheroides

Journal Article · Fri Jan 01 00:00:00 EST 1971 · Methods in Enzymology

DOI:https://doi.org/10.1016/s0076-6879(71)23145-1· OSTI ID:4060925

Clayton, Roderick K. ^[1]; Wang, Richard T. ^[1]

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1. Cornell Univ., Ithaca, NY (United States)

Here in this chapter discusses the photochemical reaction centers from Rhodopseudomonas spheroids. The hallmark of the known bacterial photosynthetic reaction centers is the presence of a bacteriochlorophyll (BChl) molecule that is specialized to act as a primary photochemical electron donor. This BChl, called “P870,” “P890,” and so on, after the wavelength of its long-wave absorption maximum, is oxidized by light, while an unspecified electron acceptor becomes reduced. Oxidation of P870 is signaled by loss of the long-wave absorption band (bleaching). In living cells, the oxidized P870 is reduced by one or more c-type cytochromes. In purified reaction centers, the source of electrons for the re-reduction of oxidized P870 depends on the environment. In any case, the defining assay for reaction centers is the reversible light-induced bleaching of P870. In the reaction centers made from Rhodopseudomonas spheroides or Rhodospirillum rubrum, the bleaching of P870 is accompanied by blue shift of a band near 800 nm because of another specialized BChl, P800. There appear to be two or three P800 for each molecule of P870. The absorption increase at 780 nm caused by this blue shift is often easier to measure than the bleaching at 870 nm. Rhodopseudomonas viridis contains the longer-wave pigment BChl b. Reaction centers made from this organism contain P830 and P960, analogous to the P800 and P870 of Rhodopseudomonas spheroides. The blue shift of P830 can be measured as an increase in optical density at 810 nm.

• Research Organization: Cornell Univ., Ithaca, NY (United States)
• Sponsoring Organization: US Atomic Energy Commission (AEC)
• NSA Number: NSA-25-037206
• OSTI ID: 4060925
• Report Number(s): NYO--3759-30
• Journal Information: Methods in Enzymology, Journal Name: Methods in Enzymology Vol. 23; ISSN 0076-6879
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

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