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  • 1
    ISSN: 0894-3230
    Keywords: Solvent-solute interactions ; β-carotene ; electronic absorption spectrum ; solvent effects ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvent effects on the wavenumber of the maximum of the longest wavelength electronic absorption band of all-trans-β-carotene were determined in 34 solvents. Together with results from previous studies, a data set for 51 solvents, mostly non-hydrogen bond donors, was constructed. This information was analyzed in terms of reaction field models and also showed its value for correlation purposes when used either alone or in combination with standard empirical solvent polarity-polarizability scales. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 159-167 
    ISSN: 0006-3592
    Keywords: amino acid ; flor yeast ; L-proline ; urea ; wine aging ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Urea, ammonium, and free amino acid contents were quantified in biological aging of a young wine under two flor film forming yeast strains, Saccharomyces cerevisiae race capensis and S. cerevisiae race bayanus, and compared. Cell viability in the film was different for the two yeast strains. Thus, capensis maintained a much greater number of viable cells per surface area than bayanus and hence used greater amount of nitrogen compounds. The main source of nitrogen for the yeasts during the biological aging process was L-proline. The two yeast strains also differed in the amounts of assimilable nitrogen they utilized, in their preferences for amino acid consumption, and kinetics. To accelerate the aging process, the effect of controlled monthly aeration of the wine aged with capensis strain was investigated. The results revealed that short aeration did not appreciably increase the overall consumption of assimilable nitrogen, but consumption of some nitrogen compounds was accelerated (particularly L-proline, L-tryptophan, L-glutamic acid, ammonium ion, L-lysine, and L-arginine); the use of L-ornithine was inhibited; and GABA, L-methionine, and urea were depletes. Probably the aeration increases the aroma compounds, thereby producing wines with improved sensory properties. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13C NMR ; 15N NMR ; 27Al NMR ; isothiocyanate ; complexes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A multinuclear magnetic resonance (NMR) study of the complexes of aluminum(III) with isothiocyanate ion in water-acetone mixtures has been completed. At temperatures low enough to slow proton and ligand exchange, separate resonance signals are observed for coordinated and bulk H2O (1H) and NCS- (13C, 15N), and Al3+ (27Al) in each complex. The 1H NMR spectra reveal six sets of signals for the complexes, [Al(H2O)6]3+ through [Al(H2O)(NCS)5]2-, including isomers for three of the species. Signal area measurements show a decrease in the Al3+ hydration number with increasing NCS- concentration, as this anion replaces water in the solvation shell. In the 27Al NMR spectra of these systems, signals for seven complexes, [Al(H2O)6]3+ through [Al(NCS)6]3-, are observed, with chemical shifts increasing by about 6 ppm with each additional NCS-. Although broadened somewhat by the Al(III) quadrupole, the 13C and 15N NMR spectra also reveal coordinated NCS- signals for these complexes, including 27Al—N13CS J-coupling in [Al(NCS)6]3-. Area evaluations of the 15N NMR signals provide an excellent complement to the 1H hydration number data. These NMR results demonstrate that a multinuclear approach to the study of solution complexes can provide detailed structural information about the species being formed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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