PROJECT SUMMARY/ABSTRACT A large group of major and minor users of X-ray diffraction instrumentation at Fred Hutchinson Cancer Research Center in Seattle are applying for NIH support through the S10 Shared Instrumentation Grant Program (SIG) for replacement and upgrade of aging X-ray diffraction equipment in the center’s Structural Biology core facility. This equipment is needed for ongoing, daily data collection and analyses to support at least 11 separate NIH-funded research projects at the center that include studies supporting targeted genome modification, cancer immunology, virology and vaccine development, and protein engineering. We propose to acquire, install and operate a unified, integrated system that optimizes the flux and optical qualities of incident x-rays and the quality and efficiency of data collection, while ensuring the most reliable operation and maintenance of that equipment through partnership with a single vendor. We require instrumentation that enables our investigators to work with extremely small and / or otherwise very weakly diffracting crystals, crystals with large unit cell dimensions, and crystallographic projects that rely primarily on sulfur or iodine SAD phasing (that are best performed using in-house X-rays corresponding to the Cu-Kalpha source). Accordingly, the brightness and wavelength of the X-ray source is of utmost importance, as well as the sensitivity, dynamic range, spatial resolution and point spread function and signal-to-noise characteristics of the X- ray area detector. The availability of flexible and powerful tools in the data analysis software are additional critical factors of consideration. Moreover, the system should be capable of full software control of hardware components, including the X-ray source, X-ray divergence, goniometer, detector and cryosystem. Diffraction data formats and processing output must be fully compatible with third party data processing and structure solution software. After extensive consultation and analyses, it is our conclusion that the essential requirements for this instrument can best be served by the XtaLAB Synergy-R (Cu-Kalpha) instrument from Rigaku Oxford Diffraction. We provide details and justification of the need for this instrumentation through the presentation of four connected issues: 1. The need for replacement of the existing instrumentation due to age and obsolescence. 2. The need for downsizing + upgrade of the existing instrumentation. 3. Need based on existing NIH-funded crystallographic projects at the center. 4. Lack of alternative instrumentation at Fred Hutch or elsewhere in the greater Seattle area.