Funds are requested for a LTQ Orbitrap XL ETDTM hybrid FT mass spectrometer, from Thermo Scientific to be used in research important in national defense, vaccine development, and for understanding chemical toxicity, kinase signaling, and pathogenicity of disease. Liquid chromatography separations of protein digests, specifically coupled to sensitive and very accurate tandem mass spectrometry, and whole protein accurate measurements coupled to top-down protein gas-phase sequencing, are highly needed proteomics capabilities for existing NIH-funded investigators at the University of Arizona. This instrument will add value to our LC-MS applications, specifically for those that absolutely require increased confidence of peptide sequencing due to accurate mass measurements of fragment ions (~2 ppm), identification of PTMs using ETD, identification of more highly-charged cross-linked peptides, as well as whole protein mass measurements of small proteins. This system will join the existing instrumentation infrastructure of the Arizona Proteomics Consortium at the University of Arizona. Obtaining this instrument will greatly increase the productivity of our research, and it is critical for the NIH-funded investigators supporting this application, who have all performed LC-MS in the past using current instrumentation but who now have a need for a high-throughput accurate proteomics mass spectrometer. Currently no such proteomics system exists, despite the variety of mass spectrometric analyses that can be performed on campus. The Thermo Scientific LTQ Orbitrap XL ETDTM hybrid FT mass spectrometer has been shown to be extremely reliable for proteomics applications. Acquisition of this instrument is being supported by NIH-funded investigators at the University of Arizona from the Department of Chemistry and Biochemistry, (College of Science Medicine (College of Medicine), Molecular and Cellular Biology (College of Science), Pharmacology and Toxicology (College of Pharmacy), Physiology (College of Medicine), as well as by various other NIH-funded external users. The Arizona Proteomics Consortium will also make the instrument available for numerous minor users on campus who have a need for other such specific uses as proposed here. The strategic research areas of focus for use of this upgraded instrument will be (1) identification and characterization of proteins in mixtures or of purified proteins of members of the Pacific Southwest Regional Center for Excellence in Biodefense and Emerging Diseases, (2) characterization of cross-linked peptides and proteins, and (3) top-down investigations of small proteins. Manufacturer demonstration data and that from several of our users are presented which clearly showcase the need and utility for this mass spectrometer. The support system at the University of Arizona exists in terms of experienced personnel, organizational and management abilities and usage track record, making acquisition of the LTQ Orbitrap XL ETDTM hybrid FT mass spectrometer a logical choice to handle the MS-based research and scientific challenges of the future. PUBLIC HEALTH RELEVANCE: Protein identification using mass spectrometry relies heavily on the ability to obtain extremely accurate mass measurements. The requested instrument will greatly enhance our ability to do just that and to identify with greater confidence proteins important for national defense, vaccine development, and those important for increasing our understanding of chemical toxicity, protein signaling, and pathogenicity of disease. The requested mass spectrometer will fit into the fleet of environmentally proteomic tools and protocols available at the Arizona Proteomics Consortium, which is staffed by eight employees consisting of Ph.D, MS and BS-level scientists. In addition, the requested instrument will be used as a training tool, like all the rest of our hardware, for current and future undergraduate and graduate-level students actively engaging in health-related research.