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Comparison of permeant ion uptake and carotenoid band shift as methods for determining the membrane potential in chromatophores from Rhodopseudomonas sphaeroides Ga.

Authors
  • S J Ferguson
  • O T Jones
  • D B Kell
  • M C Sorgato
Publication Date
Apr 15, 1979
Source
PMC
Keywords
License
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Abstract

1. A comparison was made of two methods for estimating the membrane potential in chromatophores from Rhodopseudomonas sphaeroides Ga. Illuminated chromatophores generated a potential that is apparently much larger when estimated on the basis of the red-band shift of carotenoids rather than from the extent of uptake of the permeant SCN- ion. 2. In contrast, when the chromatophores were oxidizing NADH or succinate the uptake of SCN- indicated a larger membrane potential than was estimated from the carotenoid band shift. 3. The extent of SCN- uptake and the carotenoid-band shift respond differently to changes in the ionic composition of the reaction medium. 4. The effects of antimycin on the carotenoid band shift and SCN- uptake are reported. 5. It is concluded that the carotenoid band shift and the uptake of SCN- are responding to different aspects of the energized state.

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