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  • ENDOR spectroscopy  (1)
  • Sulphur-nitrogen heterocycles  (1)
  • excitation delocalization  (1)
  • 1
    ISSN: 1573-5079
    Schlagwort(e): bacterial reaction center ; charge transfer ; excitation delocalization ; ENDOR ; primary donor ; triplet states
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The photoexcited triplet states of bacteriochlorophyll a, 3BChl a, and of the primary donor in reaction centers of Rhodobacter sphaeroides R-26, 3P865, are investigated by pulsed EPR and ENDOR spectroscopy. In 3P865 a splitting of ENDOR lines and reduction of corresponding positive and negative hyperfine couplings as compared with the monomeric 3BChl a is observed. This indicates an asymmetric distribution of the triplet excitation over the two BChl a moieties, PL and PM, forming 3P865. Based on the signs of the hyperfine couplings and on a comparison with the cation and anion radical of BChl a an assignment to nuclei in the different dimer halves is proposed. This yields an estimate for the extent of delocalization of the triplet excitation over PL and PM and for the charge transfer contribution of 3P865.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 288-294 
    ISSN: 0749-1581
    Schlagwort(e): ESR ; ENDOR/TRIPLE ; Dithiazolidinyl free radicals ; Sulphur-nitrogen heterocycles ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of related dithiazolidin-2-yl free radicals prepared from cyclic strained alkenes and tetrasulphur dinitride, and an attempt was made to relate the nitrogen and proton hyperfine coupling constants to the radical structures. The radical made from dimethoxybenzonorbornadiene was studied by ENDOR and it was found that isotopic substitution with 15N gives well resolved ENDOR spectra; the TRIPLE measurements showed that the 14N coupling constants are positive whereas all the resolved proton coupling constants are negative.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 173-194 
    ISSN: 0570-0833
    Schlagwort(e): ENDOR spectroscopy ; Spectroscopy ; Free radicals ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The name “ENDOR” has been known since biblical times and denotes a small town close to the Sea of Galilee (ca. 1000 B.C., 1 Sam. 28 : 7 ff). The acronym “ENDOR” (Electron Nuclear DOuble Resonance) characterizes the extension of electron spin resonance to electron-nuclear double resonance spectroscopy, a method that has opened up new dimensions for the investigation of complicated paramagnetic molecules. Only ENDOR spectoscopy, which has achieved technical perfection in the last decade, overcomes the resolution limitations of EPR spectroscopy, thus allowing interesting applications in the field of biochemistry. ENDOR investigations of the primary process of photosynthesis, of the mode of action of derivatives of vitamin E and K, and of the mechanism of the enzymatic catalysis of flavoenzymes in biological redox-chains have opened up new vistas. ENDOR and its extension to the triple resonance experiment TRIPLE offer, for example, the potential for a precise determination of hyperfine coupling constants, including their signs, which are frequently especially interesting. In addition to protons, a multiple of magnetic nuclei can be studied by ENDOR, such as e.g. 2H, 13C, and 14N. The ENDOR techniques is not restricted to monoradicals, but can also be applied to polyradicals in spin states of higher multiplicities (triplet, quartet, or quintet state). The experimental data accessible from ENDOR yield information about spin and charge density distributions, and about the geometrics of radicals and their internal dynamics; they also provide an excellent test for the accuracy of quantum mechanical calculations.
    Zusätzliches Material: 23 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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