Closed Loop MAS DNP NMR at K for Affordable Dramatic Gains in S N

DESCRIPTION provided by applicant NMR is arguably the most powerful analytical technique for structure determination and function elucidation in molecules of all types but there are complex challenges for biological macromolecules Dynamic Nuclear Polarization DNP with Magic Angle Spinning MAS has recently demonstrated S N gains of up to two orders of magnitude at K the lower temperature bound using N MAS technology compared to conventional NMR MAS in many solids Despite this enormous benefit the adaptation rate of DNP will be severely limited by its very high price tag $ M mostly because DNP experiments at field strengths greater T and operating in the K range require an expensive gyrotron for the high power millimeter wave mmw irradiation and that in turn requires a special magnet with superconducting sweep coils Preliminary experiments at K that consumed liquid helium at the rate of up to L day have shown the potential for the use of low power solid state mmw sources and order of magnitude higher S N for DNP if suitable MAS DNP probes could be developed However K MAS DNP will necessitate helium recycling improved sample spinner designs and a number of additional technical advances This SBIR project will enable K MAS DNP by developing A the needed high stability K helium spinner technology B the needed high efficiency closed loop cryogenic helium recycling system C complete quad resonance and quint resonance multi nuclear H F X Y e and H F X Y Z e DNP probes with auto sample exchange and variable temperature VT operation from K to K The probes will be demonstrated at T T T and T using a combination of facilities at DSI the National High Magnetic Field Laboratory and customers Compared to current state of the art K MAS DNP instrumentation the proposed fully optimized MAS DNP probes at K will often improve sample throughput by one to two orders of magnitude The information needed for determining detailed molecular structures could then be obtained on many complex biomolecules catalysts and other solids in a few hours rather than days or weeks As demonstrated during the Phase I the combination of increased Boltzmann factor dramatically reduced rf circuit noise temperature and substantially increased circuit Q combine to yield most of these throughput gains Additional significant gains will come from incorporation of a gradient coil for coherence selection Reduction in system cost will stem from the dramatic increase in T e below K enabling the use of low cost solid state millimeter wave sources and standard wide bore magnets The helium purification and recycling system this project will develop to enable K DNP will also make it straightforward and cost effective for the facility to implement recycling fo all the helium it requires for its cryo magnets The additional hardware required for helium liquefaction will be relatively minor Hence not only will this project advance throughput of solis NMR by more than an order of magnitude it will also enable cost effective recycling of helium at the larger NMR facilities PUBLIC HEALTH RELEVANCE Thousands of researchers regularly use Nuclear Magnetic Resonance NMR techniques A majority of the applications is now driven by the need for structure and function determination in biological macromolecules The advances developed under this project will make it possible for any NMR laboratory that has a wide bore magnet to begin applying Dynamic Nuclear Polarization DNP to solids on a budget they will be able to afford This would equip biomedical researchers with superb new tools for the structure function studies of biological macromolecules