The goal of this proposal is to provide a multiwire proportional counter area X-ray detector for use in macromolecular crystallographic structure determinations in the Molecular Biophysics Department of the Medical Foundation of Buffalo. This equipment is to be shared by a major group consisting of six principal investigators who are conducting research pertinent to seven peer-reviewed projects presently funded by the PHS and one project presently undergoing peer-review. The requested funds will be used to purchase not only a pair of area detectors but also a goniostat, a device for cooling crystals, an obligatory dedicated VAXstation, and necessary upgrades to an existing Rigaku rotating anode. An internal advisory committee consisting of the Foundations's President, Research Director, and the Head of the Molecular Biophysics Department will have overall responsibility for the equipment, and the day-to-day management will be provided by the two staff scientists who presently supervise the Foundation's shared diffraction facilities. Three members of the Foundation's staff have prior experience in the use of area detectors. The protein structure determination projects to be served by this equipment include the study of steroid metabolizing enzymes, steroid transport proteins, ion-transport antibiotics, dihydrofolate reductase/inhibitor complexes, transthyretin complexes, complexes of aromatase with monoclonal antibodies, insulin, antitumor antibiotics, and the gluconegenic enzyme fructose-1,6-diphosphatase.