Highly Efficient Polarizing Agents for MAS‐DNP of Proton‐Dense Molecular Solids

Efficiently hyperpolarizing proton-dense molecular solids through dynamic nuclear polarization (DNP) solid-state NMR is still an unmet challenge. Polarizing agents (PAs) developed so far do not perform well on proton-rich systems, such as organic microcrystals and biomolecular assemblies. Herein we introduce a new PA, cAsymPol-POK, report outstanding hyperpolarization efficiency 12.76 kDa U-13C,15N-labeled LecA protein pharmaceutical drugs at high magnetic fields (up to 18.8 T) fast magic angle spinning (MAS) frequencies 40 kHz). The performance of cAsymPol-POK rationalized by MAS-DNP simulations combined with electron paramagnetic resonance (EPR), density functional theory (DFT) dynamics (MD). This work shows that this biradical compatible challenging applications unlocks the rapid acquisition 13C–13C 15N–13C correlations natural isotopic abundance, which are key experiments for structure determination.