Neutron diffractometer for protein crystal covering large-unit-cell crystal at J-PARC

Kurihara, Kazuo; Tomoyori, Katsuaki; Tamada, Taro; Kuroki, Ryota

Molecular interaction study based on structural analysis of proteins like membrane proteins and protein complexes are an important research field in recent biological science. However, many of the target proteins have larger molecular weight and then unit cells of their crystals have larger volume, which is out of range of measurable unit cell volume for conventional diffractometers for neutron protein crystallography. Therefore, our group had designed the diffractometer which is able to cover such a crystal with large unit cell volume (target lattice length: 250). This proposal was accepted by Neutron Instrument Program Review Committee of J-PARC in September 2012. Larger unit cell volume causes a problem to separate spots closer to each other in spatial and time distribution in diffraction images. Therefore, our proposed diffractometer adopts longer camera distance (800 mm) and decoupled moderator as neutron source which has shorter pulse width. For covering large neutron detecting area due to long camera distance large-area detector ( 300 mm 300 mm) will be developed in collaboration with Neutron Instrumentation Section in J-PARC center. The gain factor of this diffractometer is estimated to be about 20 or larger as compared with BIX-3/4 diffractometers in JRR-3 at JAEA.