Multiscale Water Dynamics on Protein Surfaces: Protein-Specific Response to Surface Ions
Abstract
Proteins function in crowded aqueous environments interacting with a diverse range of compounds, among them dissolved ions. These interactions are water mediated. In the present study we combine field dependent NMR relaxation (NMRD) and theory to probe water dynamics at the surface of protein in concentrated aqueous solutions of hen egg-white lysozyme (LZM) and bovine serum albumin (BSA). The experiments reveal that presence of salts (NaCl or NaI) leads to an opposite ion-specific response for the two proteins: an addition of salt to LZM solutions increases water relaxation rates with respect to the salt-free case, while for BSA solutions a decrease is observed. The magnitude of the change depends on the ion identity. The developed model accounts for the non-Lorentzian shape of the NMRD profiles and reproduces the experimental data over four decades in Larmor frequency (10 kHz to 110 MHz). It is applicable 1
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