The essential synergy of MD simulation and NMR in understanding amorphous drug forms.

Molecular dynamics (MD) simulations and chemical shifts from machine learning are used to predict N, C and H chemical shifts for the amorphous form of the drug irbesartan. The local environments are observed to be highly dynamic well below the glass transition, and averaging over the dynamics is essential to understanding the observed NMR shifts. Predicted linewidths are about 2 ppm narrower than observed experimentally, which is hypothesised to largely result from susceptibility effects.