[gmx-users] vsites with NAC and opls

[chris.neale at utoronto.ca]

This is fixed, just posting for posterity.

If one wants to run pdb2gmx with -vsites hydrogens on gromacs 4.5.4 or  
4.0.7 while using the oplss ff, there is the error message:

Fatal error:
Can't find dummy mass for type opls_242 bonded to type opls_238 in the  
virtual site database (.vsd files). Add it to the database!

To fix this, one must then add the following line:

    opls_242  opls_238   MCH3A

to the [ CH3 ] section of oplsaa.ff/aminoacids.vsd