How does Dynamic Nuclear Polarization (DNP-NMR) work?
Dynamic Nuclear Polarization (DNP) is a technique that utilizes the large Boltzman polarization of the electron spin reservoir to provide a boost in NMR signal intensities by several orders of magnitude; thus increasing the data acquisition rate in a NMR experiment dramatically (1,2). In a DNP experiment the large electron polarization of a polarizing agent is transferred to surrounding nuclei (typically protons, 1H) by terahertz (microwave) irradiation near or at the electron paramagnetic resonance (EPR) transition. With signal enhancements of several orders of magnitude, the method is extremely valuable to overcome the intrinsic low sensitivity of liquid- and solid-state NMR experiments in applications ranging from particle physics (3) to structural biology (1,2) and clinical imaging (4).
DNP is no new scientific area. First DNP experiments were performed in the early 1950s at low magnetic fields (5), but until recently the technique was of limited applicability because of the lack of high-frequency, high-power terahertz sources. Today high-power, high-frequency sources such as the Bridge12 gyrotron are availalbe as turn-key instruments, making DNP a valuable and indispensable method.
- Maly T, Debelouchina G. T, Bajaj V. S, Hu K.-N, Joo C.-G, Mak-Jurkauskas M. L et al. Dynamic Nuclear Polarization at High Magnetic Fields. J. Chem. Phys 2008;128(5):052211-19.
- Barnes A. B, De Paepe G, Van der Wel P. C, Hu K. N, Joo C. G, Bajaj V. S et al. High-Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR. Apl. Magn. Reson. 2008;34(3):237-263.
- Goertz S. T. The Dynamic Nuclear Polarization Process. Nucl. Instrum. Methods Phys. Res., Sect. A 2004;526(1-2):28-42.
- Gallagher F. A, Kettuen M. I, Day S. E, Hu D.-E, Ardenkjaer-Larsen J. H, Zandt R et al. Magnetic Resonance Imaging of pH in vivo using hyperpolarized 13C-labelled bicarbonate. Nature 2008;453(7197):940-943.
- Carver T. R, Slichter C. P. Polarization of Nuclear Spins in Metals. Phys. Rev. 1953;92(1):212-213.