Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25Â K

► Probe for solid state NMR with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20 K and 9.4 Tesla. ► Signal enhancement greater than 25-fold (microwaves on versus microwaves off) using 30 mW of microwaves. ► 2D 13C-13C spectra for 160 nmol of the 26 residue peptide melittin in frozen solution, taken in ∼2½ h.