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  • 1
    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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  • 2
    ISSN: 0947-6539
    Keywords: electron transfer ; iron-sulfur proteins ; NMR spectroscopy ; proteins ; solution structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the 1H NMR spectrum of the oxidized form of the high-potential iron-sulfur protein (HiPIPI) from Ectothiorhodospira halophila, 91% of the total proton resonances and 100% of the residues have been assigned. The standard COSY, NOESY, and TOCSY sequences have been optimized for the paramagnetism of the molecule. Extensive assignment of the 15N NMR spectrum has been obtained through HMQC spectra. With 1437 dipolar connectivities, of which about 10% involved fast-relaxing protons, a family of 18 structures was generated with an RMSD of 0.65 Å by using the programs developed by Wüthrich. The family of structures was further refined by various calculation steps; the final RMSD was 0.48 Å. The structures appear to be very similar but not equal to the structures of the reduced protein. Despite the similarity in structure, significant variations in the chemical shifts are observed. A similar behavior was observed for the homologous protein from Chromatium vinosum. It is concluded that NMR is a sensitive tool to monitor differences between oxidized and reduced proteins; however, the detailed structural variations should be evaluated with caution at the present level of resolution, which roughly corresponds to a resolution of 2.5 Å in an X-ray structure.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. S145 
    ISSN: 0749-1581
    Keywords: N MR Field cycling ; Relaxation ; Relaxometry ; Metal ions ; Biological systems ; Metalloproteins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper gives an overview of the impact of relaxometry in bioinorganic chemistry. It is taken from a lecture dedicated to Seymour H. Koenig that the author presented at the 5th Chianti Workshop in Magnetic Resonance, San Miniato, Pisa, Italy, May 30-June 5, 1993. After a short introduction and the definition of relaxometry, the basic principles of field-cycling relaxometry are illustrated, with reference to the Koenig-Brown relaxometer. Through a brief survey of early relaxometric data on paramagnetic solutions dating back to the 1950s and 1960s, attention is devoted to Koenig's discovery, in the 1970s, of anomalous relaxometric profiles of metalloprotein solutions and of the theoretical problems encountered in their interpretation. Then the advances made in the 1980s in the theory of electron nucleus interactions in slowly-rotating systems are summarized. These advances were largely due to the fruitful interactions between Koenig, Bertini and his group at the University of Florence and the author, first at the University of Florence and later at the University of Bologna. After a short digression on obtaining electron relaxation rates from relaxometric measurements and on their physical meaning, recent progresses in understanding the detailed relaxometric behaviour of aqueous solutions of paramagnetic metal ions are presented. Again, Koenig's physical insight into the phenomena is highlighted. Finally, the exciting perspectives of the 1990s in the field of contrast agents, particularly in the theoretical understanding of superparamagnets, where Koenig is again at the forefront, are briefly described.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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