Abstract
Recent progress in protein x-ray crystallography has revealed many numbers of complex biological macromolecules. Structural biologists usually discuss the function of the molecules based on their atomic structures. However, most of these discussions are based on their structures without hydrogen, since atomic scattering factor (interaction with x-ray with atom) is proportional to the number of electrons and it is quite difficult to observe hydrogen by x-ray diffraction. Biological activities, or living process, is mostly based on chemical reaction of biological molecules. Not only biological macromolecules, but also water molecules and/or ions often play key roles in this process. Electron structure is also one of the most important information in chemical reaction. Atomic resolution (~ 1.2 Å) data are required to observe hydrogen and much higher data are required to observe electrons. Also, higher-resolution data reveals more solvent structures and more disordered structures. We are working on the development of subangstrom structural biology as a collaborative program, and crystallization under microgravity is a key tool for the project.
