Hybrid NMR: A Union of Solution- and Solid-State NMR
Hybrid NMR (hdNMR) is a powerful new tool that
combines the strengths of solution- and solid-state NMR to measure dipolar,
chemical shift, and quadrupolar tensors in aqueous solution. We introduce the
theory of hdNMR and partially randomly oriented (PRO) crystalline hydrogel
samples. PRO samples produce randomly oriented spectra with characteristic
Pake patterns from the solid state, yet they maintain the high-resolution
dispersion of solution NMR experiments. With new pulse sequences, we show how
hdNMR can be used to measure with high precision the
1Hα–13Cα dipolar
tensor and carboxylate chemical shift anisotropy tensor of aspartate. These
measurements contain detailed information on the distribution of electron
density, interatomic distances, and the orientation dependence of molecular
motion.