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  • 1
    ISSN: 1572-8773
    Keywords: Copper ; Cobalt ; Nickel ; Superoxide dismutase ; Alkaline phosphatase ; NMR ; Relaxometry ; Nuclear relaxation ; Electronic relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The water-proton nuclear-magnetic-relaxation dispersion profiles have been analyzed for Cu2Zn2-superoxide dismutase (SOD) and Cu2-alkaline phosphatase (AP). The electronic relaxation times are derived, together with structural information. The effect of magnetic coupling with another copper ion in Cu2Cu2SOD and Cu2Cu2AP is discussed. It is shown that the electronic relaxation times of copper(II) essentially do not change. The opposite happens with Cu2Co2SOD, Cu2Co2AP and Cu2Ni2SOD in which fast-relaxing metal ions provide relaxation mechanisms for copper(II) as well. In these cases the systems can be studied through high-resolution NMR spectroscopy.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0887-3585
    Keywords: NMR ; iron-sulfur proteins ; nuclear Overhauser effect ; paramagnetic relaxation ; relaxation matrix analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have accounted for the effect of paramagnetism on the intensities of NOEs in a 73-residue paramagnetic metalloprotein, the reduced high-potential iron sulfur protein ISO I from Ectothiorhodospira halophila, whose solution structure had been recently solved by us. The paramagnetic effects were dealt with through a suitably modified complete relaxation matrix approach. We have then recalculated the structure through a distance geometry program by minimizing the difference between the sixth roots of the calculated and experimental NOEs.The average RMSD, calculated on residues 4-71, within the structures constituting the two families decreased from 0.67 to 0.46 Å for backbone atoms and from 1.23 to 1.06 Å for all heavy atoms. The structures in the new family are for the most part within the indetermination of the previous, less resolved, family. A few specific differences are detected and related to the presence of non-negligible paramagnetic effects, which are now properly evaluated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 29 (1997), S. 348-358 
    ISSN: 0887-3585
    Keywords: ferredoxin ; NMR ; paramagnetic ; relaxation ; solution structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The possibility of using the relaxation properties of nuclei for solution structure determination of paramagnetic metalloproteins is critically evaluated. First of all, it is theoretically and experimentally demonstrated that magnetization recovery in non-selective inversion recovery experiments can be approximated to an exponential in both diamagnetic and paramagnetic systems. This permits the estimate of the contribution of paramagnetic relaxation when dominant or sizable. Then, it is shown that the averaging of paramagnetic relaxation rates due to cross relaxation is often tolerably small with respect to the use of paramagnetic relaxation rates as constraints for structural determination. Finally, a protocol is proposed to use such paramagnetic relaxation rates, which depend on the sixth power of the metal to resonating nucleus distance, as constraints for solution structure determination of proteins. As an example, the available solution structure of the oxidized ferredoxin from Clostridium pasteurianum has been significantly improved in resolution especially in the proximity of the metal ions by using 69 new constraints based on paramagnetic relaxation. Proteins 29:348-358, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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