ISOLATION BY HIGH-PRESSURE LIQUID-CHROMATOGRAPHY, CONFIGURATIONAL DETERMINATION BY H-1-NMR, AND ANALYSES OF ELECTRONIC ABSORPTION AND RAMAN-SPECTRA OF ISOMERIC SPHEROIDENE

A set of cis-trans isomers of spheroidene (all-trans, 9'-cis, 13'-cia, 9-cis, 13-cis, 5,9'-cis, 9,13'-cia, and 5,13-cis + 13,9'-cis) were is olated from an isomeric mixture which was obtained by iodine-sensitize d photoisomerization of the all-trans isomer by means of high-pressure liquid chromatography (HPLC) using a calcium hydroxide column. The 15 -cis isomer was isolated from the reaction center (RC) of Rhodobacter sphaeroides 2.4.1. The configurations of the above isomers were determ ined by H-1-nuclear magnetic resonance (NMR) spectroscopy. The order o f elution of the isomers in HPLC is explained in terms of the interact ion between the extended all-trans part of the various cis-trans confi gurations of the conjugated backbone and the flat surface of calcium h ydroxide at the molecular level. A systematic change from a peripheral -cia toward a central-cis isomer was found, for mono-cia isomers excep t for 15-cis, in the wavelength of the (1)A(g)(-)-->B-1(u)+ absorption and in the relative intensity of the C10-C11 (C10'-C11') vs. C14-C15 (C14'-C15') stretching Raman lines. (C) 1996 John Wiley & Sons, Inc.