Our objective is to elucidate the structure-function relationships of biopolymers based on the three-dimensional structures. The structures also provide information regarding molecular evolution and the principles of the protein folding. Our results contribute to the molecular design for creating artificial enzymes, functional materials, and new drugs. Currently we are interested in the study of enzymes in energy metabolic systems and proteins functioning in brains and neurons. We use facilities at SPring-8 for x-ray diffraction experiment and at JAERI for neutron diffraction study.