Adiabatic TOCSY MAS in liquids

The effect of magic angle spinning (MAS) of liquids upon the performance of various isotropic mixing sequences is investigated. Although the mathemati cal formalism for isotropic mixing under MAS conditions is similar for both liquids and solids, the mechanism through which the coherence transfer is disturbed is different. In liquids, the use of sample spinning in the prese nce of both RF and magnetic-field inhomogeneities introduces a modulation o f the effective field, which compromises the performance of the conventiona l mixing sequences. This effect is further amplified by supercycles, which normally improve the performance of the mixing and decoupling experiments. It is demonstrated that adiabatic mixing sequences are less susceptible to such modulations and perform considerably better in TOCSY MAS experiments. The best performance of TOCSY MAS is observed under the rotational resonanc e condition when the sample appears static in the nutation reference frame. (C) 2001 Academic Press.