Combined Rietveld and stereochemical restraint refinement of a protein crystal structure

By combining high-resolution X-ray powder diffraction data and stereochemical restraints, Rietveld refinement of protein crystal structures has been shown to be feasible. A refinement of the 1261-atom protein metmyoglobin was achieved by combining 5338 stereochemical restraints with a 4648-step ( d min = 3.3 Å) powder diffraction pattern to give the residuals R wp = 2.32%, R p = 1.66%, R ( F 2 ) = 3.10%. The resulting tertiary structure of the protein is essentially identical to that obtained from previous single-crystal studies.