Yushmanov V E, Tominaga T T, Borissevitch I E, Imasato H, Tabak M
Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, Brazil.
Magn Reson Imaging. 1996;14(3):255-61. doi: 10.1016/0730-725x(95)02103-z.
The interaction of Fe(III) and Mn(III) complexes of TPPS4 with bovine serum albumin (BSA) was studied by T1 relaxation measurements of water protons and high resolution 1H NMR of the porphyrin moieties. At excess of BSA, both metalloporphyrins bind to BSA as the high spin monomers. The relaxivity of bound MnTPPS4 is significantly higher as compared to the free form in solution. When metalloporphyrins are in excess, they aggregate at the BSA surface, up to two MnTPPS4, and up to 10-15 FeTPPS4 units per BSA globule. Bound aggregates are unable to enhance magnetic relaxation of water protons due to the antiferromagnetic coupling between metal ions in the aggregates. Therefore, the dose-effect dependences for metalloporphyrins in the range of metalloporphyrin/BSA ratio of 0 to 25 at the constant BSA concentration at pH 7.4 are characterized by a local maximum at about 2 for MnTPPS4, and a global maximum at about 3 for FeTPPS4, MnTPPS4 complex is more effective than FeTPPS4 in the whole concentration range. It is suggested that the difference in binding and aggregation properties of metalloporphyrins may be relevant to their relaxation efficiency in vivo, blood transport, and biodistribution.
通过水质子的T1弛豫测量以及卟啉部分的高分辨率1H NMR研究了四苯基卟吩四磺酸（TPPS4）的铁（III）和锰（III）配合物与牛血清白蛋白（BSA）的相互作用。在过量的BSA存在下，两种金属卟啉均以高自旋单体形式与BSA结合。与溶液中的游离形式相比，结合态的MnTPPS4的弛豫率显著更高。当金属卟啉过量时，它们在BSA表面聚集，每个BSA球蛋白最多可聚集两个MnTPPS4以及最多10 - 15个FeTPPS4单元。由于聚集体中金属离子之间的反铁磁耦合，结合的聚集体无法增强水质子的磁弛豫。因此，在pH 7.4恒定BSA浓度下，金属卟啉与BSA比例在0至25范围内时，金属卟啉的剂量效应依赖性特征为：MnTPPS4在约2处有局部最大值，FeTPPS4在约3处有全局最大值，在整个浓度范围内，MnTPPS4配合物比FeTPPS4更有效。有人认为，金属卟啉在结合和聚集特性上的差异可能与其体内弛豫效率、血液运输和生物分布有关。
