After successfully introducing prototype CCD detectors into macromolecular crystallography at CHESS, core research has focused on the commissioning of the first commercial CCD detector. The San Diego Area Detector Systems CCD detector is based on a combination of the Princeton and Brandeis detectors and was designed through consultation with MacCHESS staff. The detector has an active area of 80 x 80 mm2 and uses a 1k CCD. The process has involved development of calibration algorithms, data transfer protocols and improved data collection software. Initial problems resulted from the mechanical design and vacuum system and have now been corrected. The detector was used to collect test data from lysozyme resulting in Rsym values below 3% for complete, highly redundant data sets. After initial test data, the detector was used to collect data for a variety of ongoing crystallographic projects including bovine and E.coli purine nucleoside phosphorylases, thiaminase, 5'-methylthioadenosine phosphorylase and others. All of the data was of high quality comparable to that from our highly successful Princeton CCD detectors. The San Diego CCD detector has now been made available to outside users who routinely use it to collect macromolecular data. Currently, we are developing methods for in situ calibration procedures. In the past the calibration has been performed at Princeton which requires transporting the detector. We have ordered a portable X-ray generator that produces a micro-focused, low power X-ray beam. At a distance of 1-2 meters the X-ray source produces a uniform flood field that can be used for calibration purposes. The intensity is such that calibration exposures will require less than five minutes. In the future, we plan to acquire a mosaic CCD detector from San Diego Area Detector Systems. The new detector was design with input from MacCHESS. It will have four 1k CCD modules, each with an front end active area of 94 x 94 mm2. We plan to acquire the device in late 1996 or early 1997 and then begin testing at CHESS.
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