Dynamic Nuclear Polarization

Nuclear Magnetic Resonance (NMR) is witnessing a revolution, being driven by the advent of new methods with high potential for achieving nuclear hyperpolarization. While NMR is a powerful spectroscopic tool for the characterization of molecular structure and dynamics in Chemistry and Biochemistry is well-established tool in medicine as an in vivo imaging (MRI) it suffers lack of sensitivity.  It has been recently demonstrated that new technologies based on dynamic nuclear polarization (DNP), whereby the large spin alignment characteristic of electron paramagnetic resonance is passed on to nuclear spins at low temperatures, can be used to increase the sensitivity of typical NMR and MRI experiments by >10,000 times. This dramatic gain in sensitivity promises nothing less than a true revolution in the application of magnetic resonance spectroscopy and imaging. NMR and MRI-oriented DNP experiments are currently being pursued in three different settings, each one seeking its own area of specific applications. These include (i) in situ solid-state DNP NMR investigations of the kind pioneered by Griffin et al at MIT, where polarization enhancements of ≈100-300 are sought at ≈90K and at the relatively high fields where actual high resolution solid state NMR measurements will take place; (ii) cryogenic (≈1K) solid-state DNP experiments where nuclear spins are aligned ≥10,000 times over their conventional degrees of order, and then suddenly melted and transferred to a spectrometer/scanner for an otherwise conventional liquid-state NMR/MRI measurement on the resulting metastable spin state; and (iii) in situ liquid high-field DNP NMR experiments, where polarization enhancements of ≈10 are obtained. Although there are numerous experimental results, of different amount and significance, among the three directions,  that show the potential of DNP, there are still many  open questions  and need for both methodological and technological development to realize the potential of the approach and turn it into a viable routine method.
Together with Prof. Shimon Vega we focus on understanding the underlying spin dynamics mechanisms of DNP. This is a project where high field EPR and NMR come together both in the experimental techniques, the instrumentation and the theoretical approach.

 

References

  • Vigier F.M., Shimon D., Mugnaini V., Veciana J., Feintuch A., Pons M., Vega S. and Goldfarb D. The 13C solid DNP mechanisms with perchlorotriphenylmethyl radicals – the role of 35,37Cl.  Phys. Chem. Chem. Phys. 2014, 16, 19218-19228
  • Shimon D., Feintuch A., Goldfarb D., Vega S., Static 1H dynamic nuclear polarization with the biradical TOTAPOL: a transition between the solid effect and the cross effect.  Physical Chemistry Chemical Physics 2014, 16, 6687-6699.