Medium- and Long-Distance 1H–13C Heteronuclear Correlation NMR in Solids

Abstract

A simple method for obtaining 1H–13C HETCOR solid-state NMR spectra reflecting only medium- and long-range 1H–13C correlation peaks is presented. By dephasing the magnetization of protons directly bonded to a 13C nucleus, the short-range correlation peaks, which contain limited structural information, can be cleanly suppressed without reducing the long-range cross peaks significantly. The resulting reduction of resonance overlap simplifies spectral assignment. The dephasing of the intensity of a given peak in the HETCOR spectrum traces out a 1H–13C distance-dependent REDOR curve. This medium- and long-distance (MELODI) HETCOR experiment is demonstrated on a mixture of amino acids with 13C in natural abundance. It is useful for resonance assignment of proteins and other organic solids with partial or no 13C labeling.