What is hypermobile water?: detected in alkali halide, adenosine phosphate, and F-actin solutions by high-resolution microwave dielectric spectroscopy

Experimental observation by high-resolution microwave dielectric spectroscopy of hydration properties of alkali halide ions, adenosine phosphate ions, and F-actin revealed the existence of hypermobile water (HMW) molecules around those solutes. To understand the molecular process of HMW, two theoretical approaches are reviewed here. One is based on a statistical mechanical approach to analyze the rotational freedom of water molecules around a charged particle. Another approach reports direct calculation of dielectric relaxation process of water molecules around an ion. Experimentally observed HMW molecules are theoretically explained with the significance of multi-correlations among an ion and water molecules.