Dipolar-coupling-mediated total correlation spectroscopy in solid-state 13C NMR: Selection of individual 13C– 13C dipolar interactions

Abstract

Herein is described a useful approach in solid-state NMR, for selecting homonuclear 13C– 13C spin pairs in a multiple- 13C homonuclear dipolar coupled spin system. This method builds upon the zero-quantum (ZQ) dipolar recoupling method introduced by Levitt and coworkers (Marin-Montesinos et al., 2006 [30]) by extending the originally introduced one-dimensional (1D) experiment into a two-dimensional (2D) method with selective irradiation scheme, while moving the 13C– 13C mixing scheme from the transverse to the longitudinal mode, together with a dramatic improvement in the proton decoupling efficiency. Selective spin-pair recoupling experiments incorporating Gaussian and cosine-modulated Gaussian pulses for inverting specific spins were performed, demonstrating the ability to detect informative, simplified/individualized, long-range 13C– 13C homonuclear dipolar coupling interactions more accurately by removing less informative, stronger, short-range 13C– 13C interactions from 2D correlation spectra. The capability of this new approach was demonstrated experimentally on uniformly 13C–labeled Glutamine and a tripeptide sample, GAL.