Radicals and Polyradicals for Dynamic Nuclear Polarization

Massachusetts Institute Of Technology, Cambridge MA

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Abstract

DESCRIPTION (provided by applicant): This proposal is focused on the synthesis of new molecules, polymers and gels to be used with dynamic nuclear polarization (DNP) to produce enhanced NMR signals. The PI has a continuing collaboration with Professor Robert G. Griffin of the Francis Bitter Magnet Laboratory for critical evaluation of DNP materials and DNP NMR applications. The DNP method makes use of spins associated with radicals to polarize the nuclear spins of the molecules of interest. Preliminary investigations with biradicals have shown that these molecules provide greatly enhanced signals in NMR spectra (observed enhancements of H 300 are obtained in magic angle spinning spectra of solids and H 400 in solution NMR spectra). The coupled biradical approach has allowed these high enhancements at lower concentrations than can be achieved with a mono-radical species. The lower concentrations minimize the broadening due to the paramagnetic radicals in the mixture. New improved biradicals and next generation polyradical-based fullerene structures will be synthesized and evaluated for their ability to polarize nuclear spins. Extended polyradical structures based upon polymers will be developed and evaluated for DNP activity. These latter materials will be converted into gels for the polarization of liquids and eventually DNP NMR structure studies. Anisotropic DNP gels will be produced and offer new opportunities for NMR structure determination. This research is directed at producing materials that will lead to improved analysis of the structures of biological molecules by nuclear magnetic resonance and eventually novel imaging techniques for MRI. Magnetic resonance methods suffer from low sensitivity and dynamic nuclear polarization addresses this limitation. In this process electrons are excited by microwaves and transfer magnetic polarization to nuclei to produce large sensitivity enhancements. PUBLIC HEALTH RELEVANCE: This research is directed at producing materials that will lead to improved analysis of the structures of biological molecules by nuclear magnetic resonance and novel imaging techniques for MRI. Magnetic resonance methods suffer from low sensitivity and dynamic nuclear polarization addresses this limitation. In this process electrons are excited by microwaves and transfer magnetic polarization to nuclei to produce large sensitivity enhancements.