Relative comparisons of the time constants for bulk and absorbed water have been conducted in proteins (for instance in Refs. ) and on silicate solid surfaces. Tarek and Tobias reported that the water dynamics in several proteins including solutions and hydrated states show longer time constants when compared to bulk liquid. For example, the time constant of water in a globular protein (ribonuclease) is about 3.6 times longer than that in bulk liquid. The exchange of protein-bound water to the bulk involves structural relaxation of a flexible protein host. A flexible protein can sustain the hydrogen bond between adsorbed water and its surface atoms. As a result, a longer time constant for hydrogen bonds between water and a protein host is essential for hydrated proteins. Conversely, confined and absorbed water on silicate surfaces such as glass and zeolite have shorter time constants for surface oxygen than that in bulk liquid; for example, the hydrogen-bond time constants between water and surface atoms are about one order of magnitude shorter. The rigid frameworks of these inorganic solid surfaces cannot maintain hydrogen bonds for long periods because they cannot cooperatively move with the rotational and translational motion of water molecules. Therefore, the hydrogen bonds between water molecules and surface oxygen are easily broken after only a short time. This situation is quite different from absorbed water on a protein or on an inorganic solid surface. Hydrogen-bond kinetics comparable to those of bulk water may be key to forming a unique structure such as a seven-coordinate complex with an attached water molecule and a stationary rotational axis.