Solving the crystallographic phase problem with reference-beam diffraction

Abstract

By using a reference-beam diffraction data-collection technique, it is possible to directly measure a large number of relative phases of Bragg reflections on an area detector in a typical protein crystallography experiment. The technique, being developed at Cornell, incorporates the principle of three-beam diffraction into the most common method of data collection, i.e., the oscillating-crystal method, and allows recordings of many phase-sensitive three-beam interference profiles simultaneously. Recent advances include a dedicated five-circle κ diffractometer and new data acquisition and analysis algorithms. Experimental results on a protein crystal are presented and the strategies of using the measured phases for solving crystal structures are discussed.