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  • 1
    Digitale Medien
    Digitale Medien
    Molecular Recognition of R- and T-States of Human Adult Hemoglobin by a Paramagnetic Gd(III) Complex by Means of the Measurement of Solvent Water Proton Relaxation Rate (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 9365-9366 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja00141a034
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  • 2
    Digitale Medien
    Digitale Medien
    Gd(III) complexes as contrast agents for magnetic resonance imaging: a proton relaxation enhancement study of the interaction with human serum albumin (1996)
    Springer
    JBIC 1 (1996), S. 312-319 
    Details
    ISSN: 1432-1327
    Schlagwort(e): Key words Gd(III) complexes ; Contrast agents ; Proton relaxation enhancement ; Magnetic resonance imaging ; Human serum albumin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract  The non-covalent interaction between human serum albumin (HSA) and DOTA-like Gd(III) complexes containing hydrophobic benzyloxymethyl (BOM) substituents has been thoroughly investigated by measuring the solvent proton relaxation rates of their aqueous solutions. The binding association constants (K A) to HSA are directly related to the number of hydrophobic substituents present on the surface of the complexes. Furthermore, an estimation of ΔH° and ΔS° has been obtained by the temperature dependence of K A. Assays performed with the competitor probes warfarin and ibuprofen established that the complexes interact with HSA through two nearly equivalent binding sites located in the subdomains IIA and IIIA of the protein. Strong relaxation enhancements, promoted by the formation of slowly tumbling paramagnetic adducts, have been measured at 20 MHz for complexes containing two and three hydrophobic substituents. The macromolecular adduct with the latter species has a relaxivity of 53.2±0.7 mM–1 s–1, which represents the highest value so far reported for a Gd(III) complex. The temperature dependence of the relaxivity for the paramagnetic adducts with HSA indicates long exchange lifetimes for the water molecules dipolarly interacting with the paramagnetic centre. This is likely to be related to the formation, upon hydrophobic interaction of the complexes with HSA, of a clathrate-like, second-coordination-sphere arrangement of water molecules. Besides affecting the dissociative pathway of the coordinated water molecule, this water arrangement may itself significantly contribute to enhancement of the bulk solvent relaxation rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s007750050059
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  • 3
    Digitale Medien
    Digitale Medien
    Relaxometric Determination of the Exchange Rate of the Coordinated Water Protons in a Neutral GdIII Chelate (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1499-1504 
    Details
    ISSN: 0947-6539
    Schlagwort(e): gadolinium ; NMR spectroscopy ; prototropic exchange ; rare earth compounds ; water exchange rate ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The exchange rate of the coordinated water molecule in the neutral complex [Gd(DTPA-BBA)(H2O)] (DTPA-BBA = 1,7-bis[(N-benzylcarbamoyl)methyl]-1,4,7-triazaheptane-1,4,7-triacetate or diethylenetriaminopentaacetate N,N′-bis(benzylamide)) is slower than in the parent complex [Gd(DTPA)(H2O)]2-. From the analysis of the temperature dependence of the solvent 17O NMR transverse relaxation time in an aqueous solution of the paramagnetic complex, a value of 4.5 × 105 s-1 (at 298 K) is obtained for the exchange rate of the coordinated water molecule. This rate constant does not vary in the pH range 7-12. Conversely, over the same pH range and at 298 K and 20 MHz, the longitudinal water proton relaxivity increases from 4.8 to 6.5 s-1 mM-1. The analysis of the dependence of the longitudinal water proton relaxation rate on magnetic field and temperature at pH 7 and pH 12 shows that the increase in relaxivity at basic pH has to be assigned to the contribution of the prototropic exchange at the water molecule in the inner coordination sphere of the metal ion. This exchange process is catalyzed by OH- ions (kP = 1.7 × 109 M-1 s-1 at 298 K) and causes an increase in the observed relaxivity when it occurs at a rate larger than the exchange rate of the entire water molecule. At pH 12 the limiting effect of the slow exchange rate for the coordinated water molecule is removed, and the longitudinal water proton relaxivity measured at this pH then represents the maximum value attainable for this complex.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chem.19970030918
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