THE ANOMALOUS RELAXIVITY OF MN-3+(TPPS4)
THE ANOMALOUS RELAXIVITY OF MN-3+(TPPS4)
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DOI：
10.1002/mrm.1910040306
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发表时间：
1987-03-01
影响因子：
3.3
通讯作者：
SPILLER, M
中科院分区：
文献类型：
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作者：
KOENIG, SH;BROWN, RD;SPILLER, M
据报道，（C-W。Chen等人，FEBS Lett. 168，70（1984）），Mn 3+（TPPS 4）的水溶液在20 MHz和37 ° C下具有令人惊讶的高弛豫率。C，大于大多数Mn 2+络合物，包括六水合离子。由于Mn 3+（TPPS 4）是高度稳定的，并且卟啉通常是肿瘤寻找的，我们试图通过比较Mn 3+（TPPS 4）溶液的1/T1匪RD曲线（溶剂质子的1/T1的磁场依赖性）与许多其他小Fe 3+和Mn 2+络合物的1/T1匪RD曲线来理解大弛豫率的起源。通过测量的核磁共振谱的磁偶极相互作用的弛豫理论，在一个适合于小顺磁性溶质分子的形式，我们建立的理论提供了一个很好的定量描述的所有样品的弛豫行为，并确认的弛豫MN 3+（TPPS 4）是非常高的。这种效应部分归因于卟啉络合物中Mn 3+的基态波函数的各向异性，有效地使Mn 3+离子的自旋密度比球对称S态离子更接近配位水分子的质子。此外，Mn 3+自旋的顺磁弛豫时间虽然短，但比对于非S态离子预期的要长，并且随着磁场高于约2 MHz而显著增加。在这方面，Mn 3+（TPPS 4）可以是具有特别有利于用作磁共振成像中的对比度增强剂的性质的一类分子之一。
It was recently reported (C-W. Chen et al. FEBS Lett. 168, 70 (1984)) that water solutions of Mn3+(TPPS4) have a surprisingly high relaxivity at 20 MHz and 37.degree. C, greater than most Mn2+ complexes including the hexaaquoion. Because Mn3+(TPPS4) is highly stable, and porphyrins in general are tumor-seeking, we have sought to understand the origin of the large relaxivity by comparing the 1/T1 NMRD profiles (magnetic field dependence of 1/T1 of solvent protons) of Mn3+(TPPS4) solutions with those of a number of other small Fe3+ and Mn2+ complexes. By relating the measured NMRD profiles to the theory of relaxation by magnetic dipolar interactions, in a form appropriate for small paramagnetic solute molecules, we establish that the theory affords an excellent quantitative description of the relaxation behaviour of all the samples, and confirm that the relaxivity of MN3+(TPPS4) is anomalously high. The effect is attributed, in part, to the anisotropy of the ground-state wavefunction of Mn3+ in the porphyrin complex, effectively bringing the spin density of the Mn3+ ions closer to the protons of the coordinated water molecules than would a spherically symmetric S-state ion. In addition, the paramagnetic relaxation time of the Mn3+ spins, though short, is longer than would be anticipated for a non-S-state ion, and increases substantially with magnetic field above about 2 MHz. In this regard, Mn3+(TPPS4) may be one of a class of molecules with properties particularly favorable for use as contrast-enhancing agents in magnetic resonsance imaging.