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Issue 25, 2011
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Investigations into whole water, prototropic and amide proton exchange in lanthanide(III) DOTA-tetraamide chelates

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Abstract

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.

Graphical abstract: Investigations into whole water, prototropic and amide proton exchange in lanthanide(iii) DOTA-tetraamide chelates

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Publication details

The article was received on 10 Apr 2011, accepted on 04 May 2011 and first published on 31 May 2011


Article type: Paper
DOI: 10.1039/C1DT10616C
Citation: Dalton Trans., 2011,40, 6759-6764
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    Investigations into whole water, prototropic and amide proton exchange in lanthanide(III) DOTA-tetraamide chelates

    M. Woods, A. Pasha, P. Zhao, G. Tircso, S. Chowdhury, G. Kiefer, D. E. Woessner and A. D. Sherry, Dalton Trans., 2011, 40, 6759
    DOI: 10.1039/C1DT10616C

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