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  • 1
    Electronic Resource
    Electronic Resource
    Effect of nickel(II) substitution on the resonance Raman and NMR spectra of Alcaligenes xylosoxidans azurin II: implications for axial-ligand bonding interactions in cupredoxin active sites (1998)
    Springer
    JBIC 3 (1998), S. 282-291 
    Details
    ISSN: 1432-1327
    Keywords: Key words Resonance Raman spectroscopy ; Azurin ; Cupredoxins ; Axial ligands ; NMR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Assignment of the resonance Raman (RR) spectrum of Ni(II)-substituted azurin II from Alcaligenes xylosoxidans (NCIMB 11015) using Ni isotope substitution reveals an anomalously low Ni-S(Cys) stretching frequency of 349 cm–1, suggesting the presence of significant axial-ligand bonding interactions. The X-ray crystal structure of Ni(II)-substituted azurin from Pseudomonas aeruginosa shows that there are two potential axial ligands to the Ni ion: a peptide carbonyl O at a distance of 2.46 Å, together with a long-range interaction from a methionine sulfur (S′) at a distance of 3.30 Å. Comparison of the RR properties of Ni(II)-substituted azurin II with stellacyanin (which contains an axial carbonyl ligand, but no methionine) suggests that the interaction from the carbonyl oxygen ligand alone is not sufficient to account for the weak Ni azurin metal-thiolate bond. Instead, it appears that a Ni-methionine bonding interaction is also required to explain the low Ni-S(Cys) stretching frequency in Ni(II)-substituted azurin II. This hypothesis is supported by NMR studies which show a large paramagnetic shift for the protons of the methionine side-chain. Thus, it appears that Ni-substituted azurin II is best described as five-coordinate, and that significant Ni(II)-methionine bonding interactions can occur at a distance of 3.3 Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050233
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  • 2
    Electronic Resource
    Electronic Resource
    1H NMR determination of the ionization constant of a carboxylic acid group of a haem protein in mixed aqueous-organic solvents using the super WEFT sequence (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 1036-1039 
    Details
    ISSN: 0749-1581
    Keywords: Electrostatics ; Cytochrome ; SuperWEFT ; Dielectric constant ; NOE ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H NMR spectra of ferricytochrome c-551 were obtained in a variety of miscible aqueous buffer-organic solvent mixtures. The pKa of a haem carboxyl group within this protein was measured in several such solvent systems. This work was facilitated by the use of the Super water eliminated Fourier transform (SuperWEFT) technique and this was extended to the suppression of multiple solvent resonances. Nuclear Overhauser enhancement difference experiments were combined with SuperWEFT, enabling structural data to be obtained in complex solvent mixtures. The data arising from this study are relevant to the evaluation and simulation of electrostatic effects in proteins.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260291011
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  • 3
    Electronic Resource
    Electronic Resource
    Solution phase 1H and 13C-NMR studies of some 1,4,8,11,15,18,22,25-octa-alkylphthalocyanines (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 1053-1060 
    Details
    ISSN: 0749-1581
    Keywords: Octa-alkylphthalocyanines ; phthalocyanines ; 1H NMR ; 13C NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solution state 1H NMR and 13C NMR spectral data are reported for 1,4,8,11,15,18,22,25-octahexylphthalocyanine, its zinc metallated analogue, and 1,4,8,11,15,18,22,25-octanonylphthalocyanine. Full 1H and 13C NMR signal assignments for these compounds have been made using one and two dimensional techniques supported by T1 measurements. 13C NMR spectra of the two metal-free derivatives show only three signals in the aromatic region at 100 MHz but the expected four resonances at 22.5 MHz. The apparent absence of one of these at 100 MHz is ascribed to a fast exchange process, originating from N—H⃛N⇌N⃛H—N tautomerism.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260291014
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    Paper (German National Licenses)
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