MACROMOLECULAR CRYSTALLOGRAPHIC RESULTS OBTAINED AT CHESS USING A DETECTOR INCORPORATING A CHARGE-COUPLED-DEVICE

Results from various macromolecular crystallography experiments are presented showing the effectiveness of a recently installed detector incorporating a charge-coupled device (CCD). This detector uses a 1024×1024 CCD directly coupled to an x-ray sensitive phosphor by a fiber optic taper. The pixel size at the phosphor (50 μm) results in a point spread of 80 μm full width at half-maximum. Even with the relatively small active area, 51×51 mm2, about 150 orders of diffraction can be resolved across the detector face. With this detector format, well-resolved diffraction data have been collected from unit cells with edges as large as 360 Å. In an offset configuration, the detector has been used to collect extremely high-resolution data (1 Å). A number of data sets have been collected having Rsym values in the 4%-6% range; in the case of room-temperature lysozyme, an Rsym value as small as 2.1 was obtained for a 2.5 Å resolution data set. In addition to fixed wavelength studies, the detector has also been used to collect MAD data. In all cases, the use of this detector has proven to be more efficient than using standard image plates since less x-ray exposure time and no distinct scanning step are required. Furthermore, the data quality is as good and in some cases better than those from previous image plate measurements. © 1995 American Institute of Physics.