SYNOPSISA set of cis-trans isomers of spheroidene (all-trans, 9'-cis, 13'-cis, g-cis, 13-cis, 5,9'-cis, 9,13'-cis, and 5,13-cis + 13,9'-cis) were isolated from an isomeric mixture which was obtained by iodine-sensitized photoisomerization of the all-trans isomer by means of highpressure 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 determined by 'H-nuclear magnetic resonance (NMR) spectroscopy. The order of elution of the isomers in HPLC is explained in terms of the interaction between the extended all-trans part of the various cis-trans configurations of the conjugated backbone and the flat surface of calcium hydroxide at the molecular level. A systematic change from a peripheral-cis toward a central-cis isomer was found, for mono-cis isomers except for 15-cis, in the wavelength of the 'A,--P 'B,' absorption and in the relative intensity of the C10-C11 (Cl0'-Cll') vs. C14-Cl5 (C14'-C15') stretching Raman lines.

A set of cis‐trans isomers of spheroidene (all‐trans, 9′‐cis, 13′‐cis, 9‐cis, 13‐cis, 5,9′‐cis, 9,13′‐cis, and 5,13‐cis + 13,9′‐cis) were isolated from an isomeric mixture which was obtained by iodine‐sensitized 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 determined by 1H‐nuclear magnetic resonance (NMR) spectroscopy. The order of elution of the isomers in HPLC is explained in terms of the interaction between the extended all‐trans part of the various cis‐trans configurations of the conjugated backbone and the flat surface of calcium hydroxide at the molecular level. A systematic change from a peripheral‐cis toward a central‐cis isomer was found, for mono‐cis isomers except for 15‐cis, in the wavelength of the 1Ag− → 1Bu+ absorption and in the relative intensity of the C10(single bond)C11 (C10′(single bond)C11′) vs. C14(single bond)C15 (C14′(single bond)C15′) stretching Raman lines. © 1996 John Wiley & Sons, Inc.

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Some of the low level radioactive wastes from reprocessing of spent nuclear fuels contain nitrates. Nitrates can be present in the form of soluble salts and can be reduced by various reactions. Among them, reduction by metal compounds and microorganisms seems to be important in the underground repository. Reduction by microorganism is more important in near field area than inside the repository because high pH and extremely high salt concentration would prevent microorganism activities. In the near field, pH is more moderate (pH is around 8) and salt concentration is lower. However, the electron donor may be limited there and it might be the control factor for microorganism's denitrification activities. In this study, in-vitro experiments of the nitrate reduction reaction were conducted using model organic materials purported to exist in underground conditions relevant to geological disposal. Two kinds of organic materials were selected. A super plasticizer was selected as being representative of the geological disposal system and humic acid was selected as being representative of pre-existing organic materials in the bedrock. Nitrates were reduced almost to N2 gas in the existence of super plasticizer. In the case of humic acids, although nitrates were reduced, the rate was much lower and, in this case, dead organism was used as an electron donor instead of humic acids. A reaction model was developed based on the in-vitro experiments and verified by running simulations against data obtained from in-situ experiments using actual groundwaters and microorganisms. The simulation showed a good correlation with the experimental data and contributes to the understanding of microbially mediated denitrification in geological disposal systems.

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