This proposal is a request for funds to purchase a linear ion-trap/fourier transform mass spectrometer (Thermo Finnigan LTQ-FT) to upgrade the Mass Spectrometry and Proteomics Core Facility at the University of Utah. Characterization of complex proteins and modifications is central to the specific aims of more than 80 NIH-funded researchers at the University of Utah. Currently, the institution does not have instrumentation capable of meeting the existing and growing needs of these investigators. The LTQ-FT instrument is state-of-the-art and will provide ultra-high sensitivity, high mass accuracy, high resolution, and fast scanning capabilities, enabling researchers to achieve their challenging proteomics goals. It will also have many applications in other areas of biomedical research, such as structure elucidation of natural products. Many major users have been identified with existing and future projects that will ensure immediate and continued full-capacity usage. Also, the instrument will be made available to investigators from other regional institutions. The LTQ-FT will be housed in a central mass spectrometry core facility that has been in operation for more than 25 years. It will continue to be administered by the institution within a core-facilities framework which includes monitoring by an oversight committee and an advisory committee. There is very strong institutional support for this instrument. The institution is committed to providing a state-of-the-art proteomics resource which will build a close-working, collaborative role with investigators. The institution will guarantee funding for the balance of the cost of the instrument, continued financial support, maintenance, full-time operation from expert mass spectrometrists, and appropriate space within the Proteomics Core Facility. As part of this commitment, the institution recently hired a full-time director and will hire additional Ph.D. staff to operate the instrument for users.