Digital topography with an X-ray CCD camera for characterizing perfection in protein crystals

Digital X-ray topography using an X-ray CCD camera and conventional X-ray topography using X-ray film were used to investigate tetragonal hen egg-white lysozyme (HEWL) crystals. Previously, clear dislocation images of protein crystals were mainly obtained by film methods. Earlier studies of HEWL crystals using an X-ray CCD camera mainly revealed domain structures. In the present study, dislocation images of the same HEWL crystal have been obtained by using conventional X-ray film and a digital X-ray CCD camera. The results demonstrate that digital topography using an X-ray CCD camera is an effective method for characterizing protein crystals. A series of digital topographic images were analyzed by the method developed by Lovelace, Murphy, Pahl, Brister & Borgstahl [J. Appl. Cryst. (2006), 39, 425-432]. Sub-peaks and peak broadening originating from dislocations in local rocking curves were observed. Moreover, the crystal perfection was evaluated by mapping the angular positions of the maximums and the full widths at half-maximum of local rocking curves.