Lysozyme hydration in concentrated aqueous solutions. Effect of an equilibrium cluster phase.

Water close to proteins plays a key role in determining their structural and functional properties. Despite being a subject of considerable interest, the characterization of hydration water, as far as its total amount is concerned, is still controversial and its influence on protein structure and folding is not yet fully understood. In this work, we have investigated the dielectric properties of lysozyme aqueous solutions over the frequency range where the orientational polarization relaxation of the aqueous phase occurs (from 500 MHz to 50 GHz).