[NMR paper] Direct Measurement of the Mn(II) Hydration State in Metal Complexes and Metalloproteins Through 17O NMR Linewidths.

[nmrlearner]

Direct Measurement of the Mn(II) Hydration State in Metal Complexes and Metalloproteins Through 17O NMR Linewidths.

Direct Measurement of the Mn(II) Hydration State in Metal Complexes and Metalloproteins Through 17O NMR Linewidths.

J Am Chem Soc. 2013 Oct 3;

Authors: Gale EM, Zhu J, Caravan P

Abstract
Here we describe a simple method to estimate the inner-sphere hydration state of the Mn(II) ion in coordination complexes and metalloproteins. The linewidth of bulk H217O is measured in the presence and absence of Mn(II) as a function of temperature, and transverse 17O relaxivities are calculated. It is demonstrated that the maximum 17O relaxivity is directly proportional to the number of inner-sphere water ligands (q). Using a combination of literature data and experimental data for twelve Mn(II) complexes, we show that this method provides accurate estimates of q with an uncertainty of ±0.2 water molecules. The method can be implemented on commercial NMR spectrometers working at fields of 7T and higher. The hydration number can be obtained for micromolar Mn(II) concentrations. We show that the technique can be extended to metalloproteins or complex:protein interactions. For example, Mn(II) binds to the multi-metal binding site A on human serum albumin with two inner-sphere water ligands that undergo rapid exchange (1.06 x 108 s-1 at 37 °C). The possibility of extending this technique to other metal ions such as Gd(III) is discussed.


PMID: 24088013 [PubMed - as supplied by publisher]



More...