Figure 5.
(A) 13C-detected 2D CPVC SLF spectrum of a uniformly-13C-labelled isoleucine powder sample obtained at 60 kHz MAS. 1H-13C dipolar splitting spectra for the CHα group extracted from 2D CPVC SLF spectra obtained under various conditions: with the 13C carrier frequency set at the 13Cc resonance position (B) and 10 kHz offset below the 13Cαresonance frequency (C, D, E). For (B, C, D), constant amplitude spin-locks were used for Hartmann-Hahn CP, while for (E) a ramped-CP was used with a 15% ramp size on the 13C spin-lock. For the ramped-CP, the ramp ratio is defined as (whighest-wlowest)/(whighest+wlowest).