Force field refinement from NMR scalar couplings

► We present force field refinements based on explicit MD simulations using scalar couplings across hydrogen bonds. ► This leads to h3JNC′ couplings to within 0.03 Hz at best compared to experiment. ► A classification of H-bonds according to secondary structure is not sufficiently robust. ► Grouping H-bonds into two classes and reparametrization yields an RMSD of 0.07 Hz. ► This is an improvement of 50.