Abstract— Carotenoids extracted from the reaction center (RC), the light‐harvesting complex (LH), and the chromatophore membrane of Rhodospirillum rubrum SI were analyzed by high‐performance liquid chromatography. The chemical structures and the configurations of major components were determined by means of mass, Raman, electronic absorption and 1H‐NMR spectroscopy. The results indicated: (1) 15‐cis‐spirilloxanthin is bound to RC; (2) both all‐frans‐spirilloxanthin and aII‐(ran.s‐3,4‐dihydrospirilloxanthin are bound to LH and (3) 13‐cK‐spirilloxanthin is additionally present in the chromatophore membrane. The natural selection of the carotenoid configurations, i.e. 15‐ris by RC and aW‐trans by LH, is discussed in relation to the physiological functions and the photophysical properties of isomeric carotenoids.

Resonance Raman spectra of chlorophyll a and β-carotene moieties have been observed from a photosystem II reaction-center complex containing the D-1 and D-2 polypeptides and cytochrome b-559. Examination of the CC double-bond and the keto CO stretching regions of chlorophyll a moiety has indicated that the Mg atom is five-coordinate and the keto CO is hydrogen-bonded. The resonance Raman spectrum of β-carotene moiety has suggested that this carotenoid molecule takes the all-trans form. This suggestion has been supported by an HPLC analysis of the extracted carotenoid.

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Abstract— HPLC analysis of neurosporene extracted from the chromatophore membranes of Rhodobacter spheroides G1C showed two isomeric components 1 and 2. Extract from the light‐harvesting complex (LH) gave only component 2, while extract from the reaction center (RC) mainly gave component 1. Both components were isolated, and their configurations were determined by means of (1) resonance Raman, (2) electronic absorption, and (3) 1H‐HMR spectroscopy. The configuration of component 2 originating from LH was determined to be all‐trans and that of component 1 from RC was determined to be 15‐cis. Thus, our previous configurational prediction of this particular carotenoid bound to RC, by means of resonance Raman spectroscopy, to be 15‐cis [Y. Koyama, T. Takii, K. Saiki and K. Tsukida, Photobiochem. Photobiophys.5 (1983)139–150] is confirmed.