High-resolution NMR of hydrogen in organic solids by DNP enhanced natural abundance deuterium spectroscopy
We demonstrate that high field (9.4T) dynamic nuclear polarization (DNP) at cryogenic (similar to 100 K) sample temperatures enables the rapid acquisition of natural abundance H-1-H-2 cross-polarization magic angle spinning (CPMAS) solid-state NMR spectra of organic solids. Spectra were obtained by impregnating substrates with a solution of the stable DNP polarizing agent TEKPol in tetrachloroethane. Tetrachloroethane is a non-solvent for the solids, and the unmodified substrates are then polarized through spin diffusion. High quality natural abundance H-2 CPMAS spectra of histidine hydrochloride monohydrate, glycylglycine and theophylline were acquired in less than 2 h, providing direct access to hydrogen chemical shifts and quadrupolar couplings. The spectral resolution of the H-2 solid-state NMR spectra is comparable to that of H-1 spectra obtained with state of the art homonuclear decoupling techniques. (C) 2015 The Authors. Published by Elsevier Inc.