A High-performance neutron diffractometer for biological crystallography (BIX-3)

Tanaka, Ichiro; Kurihara, Kazuo; Chatake, Toshiyuki; Niimura, Nobuo

A high performance neutron diffractometer for biological crystallography (BIX-3) has been constructed at JRR-3M in Japan Atomic Energy Research Institute (JAERI) in order to determine the hydrogen positions in biological macromolecules. It uses several recent technical innovations, such as a neutron imaging plate and an elastically bent silicon monochromator developed by the authors. These have made it possible to realize a compact vertical arrangement of the diffractometer. Diffraction data have been collected from the proteins rubredoxin and myoglobin in about one month, to a resolution of 1.5, good enough to identify the hydrogen atoms with high accuracy. By adopting a crystal-step scan method for measuring Bragg diffraction intensities, the signal to noise ratio was much better than that of the Laue method. This shows that BIX-3 is one of the best-performing machines for neutron protein crystallography in the world currently.