Jebasingh B, Alexander V
Department of Chemistry, Loyola College, Chennai-600034, India.
Inorg Chem. 2005 Dec 12;44(25):9434-43. doi: 10.1021/ic050743r.
A tetranuclear gadolinium(III) complex, [Gd4(H2O)8], of DO3A appended onto the pentaerythrityl framework was synthesized to improve the water proton relaxivity for MRI application. The longitudinal relaxivity of [Gd4(H2O)8] is 28.13 mM-1 s-1 (24 MHz, 35+/-0.1 degrees C, pH 5.6) which is 5.86 times higher than that of [Gd(DO3A)(H2O)2]. The relaxivity is based on "molecular" relaxivity of the tetramer and the r1p value is "7 per Gd". The high relaxivity of the tetramer is the result of the decrease in the rotational correlation (tauR) and the presence of eight inner-sphere water molecules (q=8). The complex exhibits pH-dependent longitudinal relaxivity, and the high relaxivity both at low and high pH (r1p=28.13 mM-1 s-1 at pH 5.6 and 16.52 mM-1 s-1 at pH 9.5) indicates that it could be used as a pH-responsive MRI contrast agent. The transverse relaxivity of the tetramer is 129.97 mM-1 s-1 (24 MHz, 35+/-0.1 degrees C, pH 5.6), and the r2p/r1p ratio of 4.6 shows that it could be used as a T2-weighted contrast agent.
合成了一种连接在季戊四醇骨架上的四核钆（III）配合物[Gd4(H2O)8]，以提高用于磁共振成像（MRI）的水质子弛豫率。[Gd4(H2O)8]的纵向弛豫率为28.13 mM-1 s-1（24 MHz，35±0.1℃，pH 5.6），比[Gd(DO3A)(H2O)2]高5.86倍。弛豫率基于四聚体的“分子”弛豫率，r1p值为“每钆7”。四聚体的高弛豫率是旋转相关时间（tauR）降低和八个内球水分子存在（q = 8）的结果。该配合物表现出pH依赖性纵向弛豫率，在低pH和高pH下的高弛豫率（pH 5.6时r1p = 28.13 mM-1 s-1，pH 9.5时为16.52 mM-1 s-1）表明它可作为pH响应性MRI造影剂。四聚体的横向弛豫率为129.97 mM-1 s-1（24 MHz，35±0.1℃，pH 5.
