Radicals and Polyradicals for Dynamic Nuclear Polarization

描述（由申请人提供）：本提案的重点是合成新的分子，聚合物和凝胶，用于动态核极化（DNP），以产生增强的核磁共振信号。PI与Francis Bitter磁体实验室的Robert G. Griffin教授持续合作，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结合的自旋来使目标分子的核自旋极化。对双自由基的初步研究表明，这些分子在核磁共振光谱中提供了极大增强的信号（在固体的魔角旋转光谱中观察到h300的增强，在溶液核磁共振光谱中观察到h400的增强）。与单自由基相比，耦合双自由基方法可以在较低浓度下实现这些高增强。较低的浓度使混合物中顺磁性自由基引起的展宽最小化。新的改进双自由基和下一代基于多自由基的富勒烯结构将被合成并评估其极化核自旋的能力。基于聚合物的扩展多自由基结构将被开发和评估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核磁共振结构研究。各向异性DNP凝胶将产生，并为核磁共振结构测定提供新的机会。这项研究旨在通过核磁共振提高对生物分子结构的分析，并最终为MRI提供新的成像技术。磁共振方法灵敏度低，动态核极化解决了这一问题。在这个过程中，电子被微波激发，并将磁极化传递给原子核，从而大大提高灵敏度。

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.