Ionophore-sensitive spectral shift of carotenoid induced by ferricyanide in chromatophores from Rhodopseudomonas sphaeroides

In chromatophores from Rhodopseudomonas sphaeroides, ferricyanideinduced a change in the absorption spectrum of carotenoid. Theionophore-sensitive part of the ferri-cyanide-induced changewas similar to that induced by light or by diffusion potential.The ferricyanide-induced change is explained by the electrochromicshift of the carotenoid spectrum by the inside-positive electricalfield change which is probably caused by the electrogenic electronflow from a membrane redox component to ferricyanide in theouter aqueous phase. The ionophore-insensitive part is probablythe response of the carotenoid in another pool to the localfield change by oxidation of bacteriochlorophyll [Okada, M.and A. Takamiya (1970) Plant & Cell Physiol. 11: 713–721]. (Received January 21, 1980; )