Protocol of refinement in neutron crystallographic analysis

The protocol of refinement in neutron protein crystallographic analysis is described in this article. During the refinement, there are several features specialized for neutron experiment: (1) the mixed chemical structure of deuterium and hydrogen atoms, (2) solvent molecules around the protein, and the deuterium exchange in the polypeptide chain. We demonstrate the example of neutron refinement steps, using rubredoxin mutant, of which neutron diffraction collected using BIX-3 diffractometer at JRR-3 in Japan Atomic Energy Agency. The X-ray refinement program of CNS was used for the present refinement. Scattering lengths, stereochemical parameters, and command input files were modified for neutron experiment. These files would be the templates for the neutron protein crystallographic analysis. (author)