[gmx-users] OPLS-AA force field

[lammps lammps]

Hi everybody,

I want to use OPLS-AA force field to do simulation for dendrimer(see the
attached files for figure and .pdb). If the pH<4.0，the tertiary amines on
the dendrimer will be protonated, i.e. (CH2)3-N will be changed to
(CH2)3-NH+.  Now, I have two questions as follows.

1. How can I use pdb2gmx to get the .gro and .itp? It seems there are not
the *residue.*

2. I don't find the suitable force field for the N in (CH2)3-NH+, How can I
deal with this?

Any suggestion is appreciated. Thanks in advance.

-- 
wende
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