High-order multiple quantum excitation in C-13 nuclear magnetic resonance spectroscopy of organic solids

Excitation and detection of high-order multiple quantum (MQ) coherences amo ng C-13 nuclear spins in singly-C-13-labeled organic solids is demonstrated experimentally. MQ signals involving at least ten quanta of spin angular m omentum are observed in nuclear magnetic resonance (NMR) measurements on po lycrystalline L-methionine-methyl-C-13 and L-alanine-1-C-13, using a time-r eversible multiple pulse excitation sequence modified specifically for expe riments on systems with weak homonuclear dipole-dipole couplings and strong inhomogeneous interactions such as anisotropic chemical shifts. The feasib ility of high-order MQ excitation and detection in C-13-labeled organic sol ids promises to expand significantly the range of applications of MQ NMR as a structural tool, to include such systems as C-13- labeled synthetic poly mers and biopolymers. (C) 1999 American Institute of Physics. [S0021-9606(9 9)01906-6].