W0291

Hydrogen and Hydration in Protein Structural Chemistry. Nobuo Niimura, Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki-ken, 319-1195, Japan.

Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins, and the development of the neutron imaging plate (NIP) became a breakthrough event in neutron protein crystallography. The general features of the NIP are reviewed. Several high resolution neutron diffractometers dedicated to biological macromolecules (BIX-2, BIX-3 and BIX-4) with the NIP have been constructed at the Japan Atomic Energy Research Institute and this has enabled high resolution (such as from 1.5Å to 2.0Å) structural analyses of several proteins to have been carried out. The crystal structures of myoglobin, wild type of rubredoxin and mutant of rubredoxin, human lysozyme, cubic insulin, DsrD and so on have been carried out using BIX. From these studies, very interesting topics relevant to hydrogen and hydration in proteins, such as hydrogen bonds, H/D exchange, acidic hydrogen atom, the role of hydrogen atoms in enzymology and thermostability, the identification of methyl hydrogen atoms and dynamical behaviors of hydration structures including hydrogen have been extracted from the structural results. Finally, a systematic procedure to grow large single crystals of proteins or nucleic acids is described.