Available methods for molecular structure determination, based primarily on x-ray crystallography and Nuclear Magnetic Resonance (NMR) solution methods, have had very limited success on the insoluble helical transmembrane proteins that are critical to biological function. Various techniques are under development to enhance the effectiveness of solids NMR, where high-speed Magic Angle sample Spinning (MAS) has been most fruitful for low-gamma nuclides. To date, MAS has not been effectively applied to proton (1H) NMR of macromolecules for a combination of instrumentation reasons that will be systematically addressed in the proposed research. Preliminary simulations using advanced Computational Fluid Dynamics (CFD) software show that a combination of (1) novel supersonic microturbine blade designs, (2) novel supersonic surface cooling techniques, and (3) advanced silicon-nitride micro-machining techniques offers the potential for a factor of 4 increase in practical spinning speed (from 12 kHz to 50 kHz) for proton NMR on temperature-sensitive, dilute, biological systems. Experiments have confirmed that pressurized rf sample coils offer the potential for a factor of four increase in i-f pulse power handling and thus improved performance of advanced line-narrowing techniques such as frequency-switched and phase-modulated Lee-Goldberg homonuclear decoupling. This Phase I project will demonstrate feasibility of supersonic surface speeds in MAS rotors with a factor of five reduction in frictional heating in both a 4 mm and a 2 mm sample rotor at 7 T. Phase II will complete the developments necessary for 1H inverse-detection in triple-resonance MAS with pulsed-field gradient at fields up to 18.8 1 (800 MHz) in narrow-bore magnets. Initial field testing at an outside institution is expected by the end of the first year in Phase II.
There are more than 3,000 high-field NMR systems installed world-wide, and annual NMR equipment sales are currently approximately $300M. There is strong medical and scientific interest in determining the structures of approximately 20,000 membrane proteins over the 10-15 years, though suitable methods are currently not available. The proposed MAS probe development could enable thousands of NMR researchers to contribute to this effort at the relatively modest system upgrade cost of $35,000-$50,000, depending on field and interests. Total upgrade market potential over the decade following completion of the Phase II exceeds $40M.
