Chapter 16: Surface Effect Dominates Water Diffusion at Nanoscopic Length Scales

Molecular-scale specificity in the empirical measurement of local water diffusivity is achievable at physiologically relevant temperatures and concentrations through the application of ¹H Overhauser Dynamic Nuclear Polarization to a variety of systems of interest. Across six case studies, we demonstrate the extension of these measurements into situations of crowding and molecular confinements. Sharp divergences are observed in local water dynamics: even as crowding and confinement exert significant influence on bulk solvent properties as a whole, surface chemical interactions remain a dominant influence on the dynamics of the far smaller populations of surface hydration water. What's more, these hydration dynamics prove responsive to local variations in surface chemistry. Case studies will showcase how functional properties of biological or synthetic systems may be modulated by surface chemical effects on hydration water dynamics.