Enhancing the sensitivity of biomolecular MAS NMR by new methods of Dynamic Nuclear Polarization

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The research project comprises two parts, with magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy as the central theme. MAS makes it possible to acquire high-resolution NMR spectra of complex chemical systems in the solid state. Because there is no need for crystallization and no principal limitations exist on size and complexity, MAS NMR can provide high-resolution structural information on systems that are scarcely accessed with other spectroscopic methods, such as amorphous materials, amyloid fibrils, membrane proteins, and catalytic sites.The first part of the project focuses on the development of new microwave pulse sequences, which provide very efficient dynamic nuclear polarization (DNP). Dynamic nuclear polarization is an essential companion of MAS NMR spectroscopy as it strongly enhances its sensitivity. Two new DNP pulse sequences were recently introduced by our research group, one of which yielded particularly high sensitivity enhancement factors. Intriguingly, we are just beginning to understand why one DNP pulse sequence is better than the other. Hence, a research project, involving both DNP experiments and advanced numerical simulations of the DNP process, is proposed, which, if successful, will fix the basic design criteria for a DNP pulse sequence.In the second part, the use of MAS NMR spectroscopy to investigate the structure of amorphous calcium carbonate (ACC) is proposed. ACC is an essential precursor phase in the highly controlled, but poorly understood formation of skeletal parts by invertebrate organisms. ACC contains structural water, in an approximately one-on-one ratio with calcium carbonate, which is released upon crystallization. In spite of considerable effort, spectroscopic information on the atomic-level structure of ACC is scarce and, as a consequence, there exists no good structural model of ACC. This part of the proposal describes how 1H-13C MAS NMR correlation spectra of various forms of ACC, which are stabilized against crystallization by biopolymers, may provide specific information on the chemical environments of structural water in ACC.