Radicals and Polyradicals for Dynamic Nuclear Polarization

描述（由申请人提供）：该提案侧重于合成新分子、聚合物和凝胶，用于动态核极化（DNP）以产生增强的NMR信号。PI与Robert G.弗朗西斯比特磁铁实验室的格里芬，对DNP材料和DNP NMR应用进行关键评估。DNP方法利用与自由基相关的自旋来计算感兴趣分子的核自旋。用双自由基进行的初步研究表明，这些分子在NMR谱中提供了大大增强的信号（在固体的魔角旋转谱和溶液NMR谱中获得了H 300和H 400的观测增强）。耦合的双自由基的方法允许这些高增强在较低的浓度比可以实现与单自由基物种。较低的浓度使由于混合物中的顺磁性自由基而导致的增宽最小化。新的改进的双自由基和下一代基于多自由基的富勒烯结构将被合成和评估其抑制核自旋的能力。基于聚合物的扩展聚自由基结构将被开发并评估DNP活性。这些后一种材料将被转化为凝胶，用于液体的极化和最终的DNP NMR结构研究。各向异性DNP凝胶将产生，并提供新的机会，核磁共振结构测定。这项研究旨在生产材料，通过核磁共振改善对生物分子结构的分析，并最终实现MRI的新型成像技术。磁共振方法的灵敏度低，动态核极化解决了这一限制。在这个过程中，电子被微波激发，并将磁极化转移到原子核，以产生大的灵敏度增强。

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.