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  • 1
    Electronic Resource
    Electronic Resource
    15N chemical shift changes in cytochrome b5: redox-dependent vs. guanidinium chloride-induced changes (2000)
    Springer
    JBIC 5 (2000), S. 761-764 
    Details
    ISSN: 1432-1327
    Keywords: Redox dependent shift Cytochromes Electron-transfer proteins NMR Folding intermediate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The origin of the recently reported chemical shift changes of backbone amide nitrogens of redox proteins upon redox state changes has been investigated. These effects are particularly marked in cytochromes and are clearly present after correction for pseudocontact shifts in the oxidized form (Boyd J, Dobson CM, Morar AS, Williams RJP, Pielak GJ (1999) J Am Chem Soc 121:9247–9248; Guiles RD, Basus VJ, Sarma S, Malpure S, Fox KM, Kuntz ID, Waskell L (1993) Biochemistry 32:8329–8340). 15N-HSQC experiments have been performed on both oxidized and reduced forms of cytochrome b5 in the absence and in the presence of 2 M guanidinium chloride (GdmCl). GdmCl in this concentration is known to sizably alter the structure of the oxidized form of the protein and, in particular, to perturb the hydrogen bonding network. However, the perturbation of the 15N-NMR chemical shift changes is minor compared to the changes occurring upon reduction. It is concluded that changes in hydrogen bonding upon reduction must be modest and cannot account for the observed chemical shift effects. Alternative explanations should thus be looked for.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750000166
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  • 2
    Electronic Resource
    Electronic Resource
    The auto-orientation in high magnetic fields of oxidized cytochrome b562 as source of constraints for solution structure determination (2000)
    Springer
    Journal of biomolecular NMR 17 (2000), S. 295-304 
    Details
    ISSN: 1573-5001
    Keywords: cytochromes ; magnetic susceptibility anisotropy ; paramagnetism ; residual dipolar couplings ; solution structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract 15N-1H 1J couplings were measured at 500 MHz and 800 MHz for 15N enriched oxidized cytochrome b 562 from E. coli. The magnetic field dependence of 70 1J values, which could be measured without signal overlap, shows that there is a molecular magnetic anisotropy which provides partial molecular orientation in the magnetic field and, consequently, residual dipolar couplings (rdc). The rdc were used as further constraints to improve the existing structure [Arnesano et al. (1999) Biochemistry, 38, 8657–8670] with a protocol which uses the rhombic anisotropy [Banci et al. (1998) J. Am. Chem. Soc., 120, 12903–12909]. The overall large molecular magnetic anisotropy has been found to be determined by both the low spin iron (III) and the four helix bundle structure magnetic susceptibility anisotropy contributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008308501053
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  • 3
    Electronic Resource
    Electronic Resource
    Lanthanide induced residual dipolar couplings for the conformational investigation of peripheral 15NH2 moieties (2000)
    Springer
    Journal of biomolecular NMR 18 (2000), S. 347-355 
    Details
    ISSN: 1573-5001
    Keywords: lanthanides ; paramagnetic ; residual dipolar couplings ; self-orientation ; side chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The Ca2 calbindin protein in which one calcium has been substituted with Ce(III), Yb(III) and Dy(III) displays substantial alignment in high magnetic fields due to the high anisotropy of the metal magnetic susceptibility. This property has allowed the measurement of residual dipolar coupling contributions to 1 J HNand 2 J HH couplings of asparagine and glutamine NH2 moieties. Such data have been used to aid structural characterization of these groups. The exploitation of auto-orientation of magnetic anisotropic metalloproteins represents a step ahead in the investigation of the conformational space of peripheral residues that are not fixed by the protein folding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026785228634
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  • 4
    Electronic Resource
    Electronic Resource
    Sulfonamide-Functionalized Gadolinium DTPA Complexes as Possible Contrast Agents for MRI: A Relaxometric Investigation (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 625-630 
    Details
    ISSN: 1434-1948
    Keywords: NMRD ; MRI ; Contrast agents ; Carbonic anhydrase ; Sulfonamides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel Gd-DTPA derivative with a built-in sulfonamide (SA) was synthesized as a contrast agent for MRI. The complex was designed to selectively target the enzyme carbonic anhydrase. It is shown that the longitudinal relaxation rates of aqueous solutions of Gd-DTPA-SA in the presence of carbonic anhydrase increase significantly. The binding constant is determined to be 15,000 ± 5,000 M-1. This value ensures substantial formation of the carbonic anhydrase adduct at imaging concentrations of Gd-DTPA-SA. The complex interacts with erythrocytes, presumably due to a high affinity for the carbonic anhydrase present on the outer surface of the latter. This takes place even though the enzyme has a low abundance and is easily saturated by small amounts of Gd-DTPA-SA. The interaction of Gd-DTPA-SA with serum proteins is negligibly small. Therefore, the complex could potentially be tested as a selective contrast agent for compartments outside the blood pool.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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