Biological water: A critique

In this overview, we provide a critique of the hydration dynamics of macromolecules, particularly those of protein and DNA. Only in the past decade has femtosecond spectroscopy enabled direct access to the ultrafast dynamical motion of surface water. With the wealth of results from this spectroscopic technique, NMR, and neutron scattering, it is now established that hydration is indeed an ultrafast phenomenon, and in this sense the 'iceberg model' is invalid. Here, we overview the experimental and the theoretical studies, hoping to clarify the confusion resulting from some recent MD simulations. We maintain that there are two types of water hydration, those that reorient in the vicinity of the surface and those which are ordered, however in dynamic interaction with the protein.