铜(Ⅱ)-L-组氨酸络合物中咪唑环碳质子核磁弛豫速率的研究

Study on proton NMR relaxation rates in imidazole of Cu (II) -L-histidine complex

用反转恢复法（１８０°－τ－９０°脉冲序列）测定了铜（Ⅱ）－Ｌ－组氨酸（浓度比为１：３００）体系中，咪唑环上 Ｃ（２）与 Ｃ（４）质子在不同 ｐＨ值的１Ｈ－ＮＭＲ顺磁弛豫速率Ｔ１Ｐ－１、Ｔ２Ｐ－１。实验结果指出，在所测的 ｐＨ范围内， Ｃ（２）质子比 Ｃ（４）质子有较大的弛豫速率。在ｐＨ３—４之间，它们的弛豫速率均出现极值。此现象表明，在上述ｐＨ范围内，Ｃｕ（Ⅱ）与Ｌ－组氨酸可能形成了较稳定的络合物。此外，还分别测定了金属与组氨酸浓度比为 １：３０， １：４５， １：３００， １：４５０体系中，咪唑环上 Ｃ（２）与 Ｃ（４）质子的纵向顺磁弛豫速率，可以看到，随着金属离子浓度增大，纵向弛豫速率也增大。

The proton NMR relaxation rates T1p-1 and T2p-1 on Cu (II) - L-histidine (concentration ratio of 1:300) have been determined in different PH values by the inversion recovery method (180'-r-90' pulse sequence). The results indicate that the relaxation rates of C(4)H in imidazole are shorter than C(2)H over PH range of measurement. In the presence of Cu(II) ion their relaxation rates show an extreme value between PH 3 and PH 4. It was deduced that Cu(II)-L-His complex was formed in that PH region. In addition, their transverse relaxation rated of C(2)H and C(4)H on Cu(II) -L-His complexes, whose concentration ratios (Metal:His) are 1:30, 1:45, 1:300 and 1:450, have been also determined. The experimental values show that the longitudinal relaxation rate increases with the increase of the concentration of paramagnetic ions.