This Shared Instrumentation Grant proposal seeks funds to upgrade a 500 MHz NMR spectrometer at the University of Texas Medical School, Houston. The upgraded instrument would have a new digital spectrometer console and an inverse triple resonance probe with actively shielded X, Y and Z-gradient coils. This will allow multidimensional, heteronuclear experiments for the structural characterization of recombinant isotopically-labeled biopolymers. The need for this critical research tool is justified at multiple levels: First, the upgraded system will provide essential instrumentation for 5 primary users with NIH funded research that requires NMR instrumentation. The research programs of these users have been severely hampered by limited time on other NMR instruments in the Houston area. The NMR facility will be an integral part of a Structural Biology Center that is being established at the University of Texas Medical School in Houston. The NMR instrumentation, together with anticipated X-ray crystallography and molecular modeling expertise in the Center, will provide a valuable resource for faculty who want to expanding the scope or their current research projects to include structural biology. The requested upgraded NMR instrument will benefit the broader community of structural biologists in Houston by relieving the backlog of experiments that must currently being performed on the two high field NMR instruments at Rice University and the University of Texas. These two facilities currently must serve scientists at UT-Houston, Rice University, MD Anderson Cancer Center, Baylor College of Medicine and the Texas A and M Institute for Biotechnology. The proposed NMR facility in the Structural Biology Center at UT-Houston will be a key component in plans to acquire very high field NMR instrumentation in the Houston area.