Spin-locking and cross-polarization under magic-angle spinning of uniformly labeled solids.

Spin-locking and cross-polarization under magic-angle spinning are investigated for uniformly 13 C and 15 N labeled solids. In particular, the interferences from chemical shift anisotropy, and 1 H heteronuclear and 13 C homonuclear dipolar couplings are identified. The physical origin of these interferences provides guidelines for selecting the best 13 C and 15 N polarization transfer rf fields. Optimal settings for both the zero- and double-quantum cross-polarization transfer mechanisms are recommended. [ABSTRACT FROM AUTHOR]