Funds are requested for acquisition of a time-of-flight mass spectrometer with an electrospray ionization source (Q-Tof). The unique features of the requested instrumentation that are critical for the research programs of the proposed users are: (i) high m/z range (up to 32,000 u) enabling detection and characterization of large intact macromolecular species; (ii) tandem capability allowing structurally diagnostic fragments of mass-selected polypeptide ions to be produced; (iii) duty cycle close to 100% allowing sensitive detection of peptide and protein ions and short acquisition times over an extended mass range. The requested instrumentation will be used to study mechanisms of assisted folding and translocation; metal binding properties and dynamics of iron transport proteins from the transferrin family and their receptors; structure and dynamics of novel redox-active proteins from superoxide dismutase family; and mechanisms of membrane signal transduction and chemotaxis. In addition, the requested mass spectrometer will be used for studies of mechanisms of protein maturation and degradation; mechanisms of RNA polymerases; as well as ribosomal architecture and dynamics. Altogether, 7 faculty members (6 of which are currently NIH funded) will use the requested instrumentation. The requested instrumentation will become a part of the Mass Spectrometry Center, which is jointly supported by three academic departments. The Director of the Center will be responsible for the daily operation and maintenance of the instrument. The cost of the instrument operation and upkeep beyond the warranty period will be recovered through users fees, a mechanism which is currently used for support of the other four mass spectrometers in the Center. The operation of the instrument will be overseen by a Mass Spectrometry Advisory committee comprised of faculty members representing three academic departments and one interdisciplinary research center at UMass. ? ?