A Technique for determining the deuterium/hydrogen contrast map in neutron macromolecular crystallography

中性子決勝解析における重水素/水素コントラストマップの決定法

茶竹 俊行*; 藤原 悟

Chatake, Toshiyuki*; Fujiwara, Satoru

A technique for the determination of the deuterium/hydrogen (D/H) contrast map in neutron macromolecular crystallography has been developed and evaluated using ribonuclease A. In this technique, the contrast map between the DO-solvent and HO-solvent crystals is calculated using subtraction in real space. The present technique can thus utilize all the amplitudes of the neutron structure factors for both of the DO-solvent and HO solvent crystals. The neutron D/H contrast maps clearly demonstrate powerful detectability of the H/D exchange in proteins. In fact, alternative protonation states and alternative conformations of hydroxyl groups are observed at a medium resolution (1.8 ). Moreover, water molecules can be categorized into three types according to their tendency for rotational disorder. These results directly indicate improvement in the neutron crystal structure analysis. Combination of this technique with the conventional neutron structure determination protocols thus makes more precise and efficient determination of the D atom positions in proteins possible.