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Direct measurement of the Mn(II) hydration state in metal complexes and metalloproteins through 17O NMR line widths.

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 line width of bulk H2(17)O is measured in the presence and absence of Mn(II) as a function of temperature, and transverse (17)O relaxivities are calculated. It is demonstrated that the maximum (17)O relaxivity is directly proportional to the number of inner-sphere water ligands (q). Using a combination of literature data and experimental data for 12 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 7 T 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 multimetal binding site A on human serum albumin with two inner-sphere water ligands that undergo rapid exchange (1.06 × 10(8) s(-1) at 37 °C). The possibility of extending this technique to other metal ions such as Gd(III) is discussed.

SUBMITTER: Gale EM

PROVIDER: S-EPMC3864583 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Direct measurement of the Mn(II) hydration state in metal complexes and metalloproteins through 17O NMR line widths.

Gale Eric M EM Zhu Jiang J Caravan Peter P

Journal of the American Chemical Society 20131024 49

Here we describe a simple method to estimate the inner-sphere hydration state of the Mn(II) ion in coordination complexes and metalloproteins. The line width of bulk H2(17)O is measured in the presence and absence of Mn(II) as a function of temperature, and transverse (17)O relaxivities are calculated. It is demonstrated that the maximum (17)O relaxivity is directly proportional to the number of inner-sphere water ligands (q). Using a combination of literature data and experimental data for 12 M ...[more]

PMID: 24088013

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Direct measurement of the Mn(II) hydration state in metal complexes and metalloproteins through 17O NMR line widths.

Publications

Direct measurement of the Mn(II) hydration state in metal complexes and metalloproteins through 17O NMR line widths.

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