Rapid visualization of hydrogen positions in protein neutron crystallographic structures.

Neutron crystallography is a powerful technique for experimental visualization of the positions of light atoms, including hydrogen and its isotope deuterium. In recent years, structural biologists have shown increasing interest in the technique as it uniquely complements X-ray crystallographic data by revealing the positions of D atoms in macromolecules. With this regained interest, access to macromolecular neutron crystallography beamlines is becoming a limiting step. In this report, it is shown that a rapid data-collection strategy can be a valuable alternative to longer data-collection times in appropriate cases. Comparison of perdeuterated rubredoxin structures refined against neutron data sets collected over hours and up to 5 d shows that rapid neutron data collection in just 14 h is sufficient to provide the positions of 269 D atoms without ambiguity.