Prototype EPR/NMR instrument for DNP-enhanced studies of biological systems using high resolution NMR microscopy and spectroscopy

Lead Research Organisation: University of St Andrews
Department Name: Physics and Astronomy


Nuclear Magnetic Resonance (NMR) spectroscopy and Magnetic Resonance Imaging (MRI) are important tools in many scientific disciplines, including medical diagnostics, molecular biology, pharmaceutical and material sciences. However, due to fundamental principles that relate to the low energy of interaction between a strong magnetic field and the weak magnetic moment of certain nuclei such as hydrogen, the sensitivity of these techniques is usually low in comparison to other spectroscopic techniques.We therefore propose in this project to design, construct and test an instrument which will enable us to generate a much stronger signal (1000 -10,000 times) than is possible with current systems. The instrument relies on exploiting the interaction between unpaired electrons, which also possess a magnetic moment, and the nuclei. Since the magnetic moment of electrons is much stronger (660 times) than that of the nuclei, the energy of the interaction of electrons with a strong magnetic field is much higher. This means that at low temperatures it is possible to produce a frozen sample in which almost all the electron magnetic moments are aligned with a strong, applied magnetic field, corresponding to nearly 100 % polarisation. It is possible to transfer this very high degree of polarisation to the nuclei using millimetre wave irradiation (94GHz) at a well defined frequency, in a process known as dynamic nuclear polarisation (DNP). Under certain conditions the high polarisation of the nuclei is conserved during a rapid thawing of the frozen sample. It can then be used in NMR experiments generating a very strong signal in comparison to that available using conventional NMR systems.However, this approach is technically very challenging since it requires the accommodation of two sample spaces within a superconductive magnet. The manufacture of such an instrument requires the interaction of two different transmitters, with GHz and MHz frequencies, the development of mechanical or pneumatic lifts, the generation and control of well defined magnetic fields and extremely low temperatures.The realisation of such a prototype instrument will have strong impact on many research areas since the generation of a much stronger NMR signal will open up a range of novel applications such as NMR microscopy with very high spatial resolution and very fast spectroscopy of the interaction of different nuclei. For instance, it will make micro-imaging and spectroscopic studies on a single cell level possible


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Leggett J (2010) A dedicated spectrometer for dissolution DNP NMR spectroscopy. in Physical chemistry chemical physics : PCCP