Medium- and long-distance 1H-13C heteronuclear correlation NMR in solids

A simple method for obtaining H-1-C-13 HETCOR solid-state NMR spectra reflecting only medium- and long-range H-1-C-13 correlation peaks is presented. By dephasing the magnetizatiorn of protons directly bonded to a C-13 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 H-1-C-13 distance-dependent REDOR curve. This medium- and long-distance (MELODI) HETCOR experiment is demonstrated on a mixture of amino acids with C-13 in natural abundance. It is useful for resonance assignment of proteins and other organic solids with partial or no C-13 labeling. (C) 2001 Academic Press.