Perdeuteration: improved visualization of solvent structure in neutron macromolecular crystallography.

The 1.8 Šresolution neutron structure of deuterated type III antifreeze protein in which the methyl groups of leucine and valine residues are selectively protonated is presented. Comparison between this and the 1.85 Šresolution neutron structure of perdeuterated type III antifreeze protein indicates that perdeuteration improves the visibility of solvent molecules located in close vicinity to hydrophobic residues, as cancellation effects between H atoms of the methyl groups and nearby heavy-water molecules (D2O) are avoided.