To consider the role of parameterization, simulations were performed with three different versions of Amber, namely Amber99SB*-ILDN 139-141 , Amber03* 140,142 , and Amber99SB- disp 143 . On the same lysine dataset, a dramatic improvement was observed with Amber99SBdisp (Figure ). Given that differences in the dihedral parameterization between Amber99SB*-ILDN and Amber14SB appeared to confer almost no performance improvement, this narrowed the likely cause of the difference to the non-bonded interactions.