For the MQMAS experiment (Fig. ), the z-filter pulse sequence was used to acquire the spectrum. The experimental parameters used were as follows: recycle delay (d1) = 0.02 s, 121,752 transients, 44 h, 3Q-conversion pulses ω 1 = 66.7 kHz, z-filter ω 2 = 20.8 kHz. 32 rows were collected in the F2 dimension. Shearing was performed using the TopSpin xfshear function. NMR analysis was performed in Topspin v4.1.4 and spectral fitting was performed in dmFit and ssNake. The quadrupolar parameter definitions used throughout this work are as follows (where the convention for PAS components utilised is