Vitzthum, V., et al., Fractional Spin-Labeling of Polymers for Enhancing NMR Sensitivity by Solvent-Free Dynamic Nuclear Polarization. ChemPhysChem, 2011. 12(16): p. 2929-2932.
Decapeptides are partly covalently labeled with a polarizing agent to enhance NMR signals by dynamic nuclear polarization (DNP). DNP under magic angle spinning conditions at T=100 K was performed directly on these molecules in the absence of any solvent.