Acquisition of an X-Ray Area Detector

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Financial support is requested for acquisition of an X-ray area detector to be used with an existing rotating anode generator Rigaku RU-200. Recent advances in image detection technology have made area detector diffractometers the instrument of choice for X-ray data collection for crystals of macromolecules. Indeed, the proliferation of these instruments is the major reason for the recently observed rapid increase in the number of protein structures published annually. There is no X-ray area detector in the State of South Carolina. Our present selection of the detector is R-AXIS II produced by Rigaku and marketed by the Molecular Structure Corporation. The resulting facility will be operated as X-ray Diffraction Laboratory of Institute of Biological Research and Technology at the University of South Carolina. The facility will be used primarily for the crystallographic structure determination of biological macromolecules. Immediate applications include studies of a series of enzymes: chloroperoxidase/dehalogenase, formyltetrahydrofolate synthase, transcarboxylase, enolase, glutaminase/asparaginase, prostatic acid phosphatase, and thymidylate synthase. We will also study the bioincorporation of tellurium into proteins in the form of derivatized amino acids telluromethionine and tellurotryptophane. Recently, area detectors are frequently used also in "small molecules" crystallography. With Mo K radiation, they routinely provide data sets as good as conventional diffractometers but in much shorter time. For large "small molecules" such as metal cluster complexes with organic ligands, area detectors, even with Cu K radiation, offer important advantages. We would like to use the area detector to collect data for the structure analyses of metal clusters with large unit cell dimensions and poor stability in the X-ray beam. The Department of Chemistry and Biochemistry offers graduate course CHEM745 "Introductory Crystallography" every second year. In Spring 1993 the enrollment was 10 students. The area detector diffractometer will be used to train students in state-of-the art data collection techniques.