Hydration of proteins and DNA determined by neutron

The significance of structural study on the hydrations of protein and DNA was briefly described and the analyzing methods for the study were outlined. Hydrogen (H) bond is involved in most of the bondings in hydration structure of protein. So, it is important to determine the positioning of H bond in protein. A working hypothesis that water molecule surrounding DNA is a tag by which protein can easily recognize the position for specific bonding to DNA was proposed. Thus, it became necessary to obtain informations on the network of water molecules hydrated to DNA. Neutron is an useful probe able to provide some conclusive evidence for such roles of water molecule. Neutron diffraction method can provide 3-dimensional structures of biomolecules such as H atom and hydrated water. The data collecting speed was improved by 10 times through the author's development of neutron imaging plate. However, the intensity of neutron source is more than several orders of magnitude lower than that of X-ray source at present. In addition, single crystal larger than 1 mm3 is needed to obtain sufficient data for structural analysis using neutron diffraction method. The authors successfully determined the positions of H atoms in 157 hydrated water molecules of egg white lysozyme. (M.N.)