- 作者: Tsan-Hwang Chenga, Kuei-Tang Lina, Ming-Hung Oua, Hsiu-Ling Shiha, Gin-Chung Liub and Yun-Ming Wanga
- 中文摘要: The water 1H and 17O NMR relaxation properties of aqueous solutions containing Gd(III) chelates of the DTPA-BIPA, DTPA-BAA, DTPA-BDEA and DTPA-BMA ligands were investigated, and the results were compared with those previously reported for the Gd(III) complex with DTPA ligand. The significant deviation from the monoexponential behavior at the estimation of temperature dependence of 1H longitudinal relaxation rate for Gd(III) complexes with DTPA-BIPA, DTPA-BAA and DTPA-BDEA ligands is characteristic of the slow chemical exchange. The measurements of 17O NMR transverse relaxation rates and EPR transverse electronic relaxation rates in the range 276-343 K, allowed the assessment of the water-exchange lifetime between the coordination site and the bulk solvent. With this approach, we obtained the water-exchange lifetime(τM) of 1515, 1429, 1538 and 2128 ns for [Gd(DTPA-BIPA)(H2O)], [Gd(DTPA-BAA)(H2O)], [Gd(DTPA-BDEA)(H2O)] and [Gd(DTPA-BMA)(H2O)], respectively. Compared with the τM value of 303 ns for [Gd(DTPA)(H2O)]2-, we are able to conclude that the water residence lifetime increases when the two terminal carboxylate groups of DTPA were substituted by two amide groups.
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