[gmx-developers] OPLS FF Dihedrals for residue NAC

[Walter Ash]

A dihedral definition for the residue NAC (N-acetyl cap) is missing from 
ffoplsaabon.itp, as distributed with gromacs 3.4.1.  

I fixed this by adding:

  CT_2   C      N      CT      3     30.30825  -4.81482 -25.49343   
0.00000   0.00000   0.00000 ; For NAC cap.

which is just a copy of the similar peptide bond dihedral, with the 
methyl group's atom type.

  CT_2   C      N      CT_2    3     30.30825  -4.81482 -25.49343   
0.00000   0.00000   0.00000 ; peptide - V1 changed to 2.3