Investigations into whole water, prototropic and amide proton exchange in lanthanide(III) DOTA-tetraamide chelates
Investigations into whole water, prototropic and amide proton exchange in lanthanide(III) DOTA-tetraamide chelates
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DOI：
10.1039/c1dt10616c
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发表时间：
2011-01-01
影响因子：
4
通讯作者：
Sherry, A. Dean
中科院分区：
文献类型：
--
作者：
Woods, Mark;Pasha, Azhar;Sherry, A. Dean
自从发现水交换动力学受到从醋酸酯侧链供体向酰胺侧链供体的转变的显著影响以来，DOTA-四酰胺配体的稀土(III)络合物一直是一个特别感兴趣的领域。最近，这些螯合物作为潜在的PARACEST试剂吸引了人们的兴趣，用于磁共振成像。在这篇文章中，我们报告了使用化学交换饱和转移(CEST)和一些最近报道的螯合物来重新检查这类络合物中的交换过程的研究结果。我们发现Parker和Aime的结论在很大程度上是固体的；水的交换是缓慢的，在水溶液中发生了大量的原生交换。当pH高于8时，原生性交换的程度增加，导致在高pH时有更高的松弛。然而，研究发现，在高pH值下，酰胺质子对弛豫度的贡献很小。
Lanthanide(III) chelates of DOTA-tetraamide ligands have been an area of particular interest since the discovery that water exchange kinetics are dramatically affected by the switch from acetate to amide side-chain donors. More recently these chelates have attracted interest as potential PARACEST agents for use in MRI. In this paper we report the results of studies using chemical exchange saturation transfer (CEST) and some more recently reported chelates to re-examine the exchange processes in this class of chelate. We find that the conclusions of Parker and Aime are, for the most part, solid; water exchange is slow and a substantial amount of prototropic exchange occurs in aqueous solution. The extent of prototropic exchange increases as the pH increases above 8, leading to higher relaxivities at high pH. However, amide protons are found to contribute only a small amount to the relaxivity at high pH.