Improving spectral resolution in biological solid-state NMR using phase-alternated rCW heteronuclear decoupling

The successful application of solid-state NMR spectroscopy for structural study of biological macromolecules requires high spectral resolution. In presence of abundant H-1 spins, the resolution of the prevailing C-13 or N-15 chemical shift encoding experiments critically depends on the availability of efficient and robust heteronuclear decoupling methods in addition to the use of high-field instrumentation and fast sample spinning. Robustness of the decoupling method towards alterations in amplitude/offset of radio frequency fields due to varying sample states is important to ensure recording of spectra with high resolution over long sampling periods for insensitive samples. Here, we present a phase-alternated refocused continuous-wave decoupling method offering better resolution, easier setup, and higher robustness than previous methods. Improved decoupling is in part ascribed to more efficient cancellation of the residual heteronuclear, H-1-C-13, dipolar coupling interactions which are induced by homonuclear, H-1-H-1, dipolar coupling interactions. (C) 2015 Elsevier B.V. All rights reserved.