The Dissolution-Dynamic Nuclear Polarization Experiment.

Dissolution-Dynamic Nuclear Polarization (D-DNP) addresses the most pressing issue of nuclear magnetic resonance spectroscopy - low sensitivity. In D-DNP the analyte is mixed with a radical in a glass-forming matrix. This substrate is frozen and kept at low temperature (<100 K) and a magnetic field of several Tesla. By using microwave irradiation, polarization is transferred from electron spins to nuclear spins. The substrate is then liquefied, and the liquid-state signal of the nuclear spins is observed in a high-resolution nuclear magnetic resonance (NMR) magnet or a magnetic resonance imaging scanner. The D-DNP technique has enabled spectacular experiments, such as the in vivo observation of human metabolism. However, unlike other sensitivity enhancement methodologies, such as cryoprobes or magic angle spinning (MAS) DNP, D-DNP is not applied broadly in NMR spectroscopy at present. Here, we describe (i) the gains of an ideal D-DNP experiment for NMR spectroscopy, and contrast them with the real implementations of the D-DNP experiment available today, with a focus on applications in spectroscopy. We review principles of (ii) the dynamic nuclear polarization step and (iii) the sample transfer. We argue (iv) that stringent automation is essential for broader adaptation of the D-DNP experiment.