[gmx-users] Charmm27 and Charmm36 atomtypes assignments for polymer

[Mijiddorj B]

Dear Gmx users,

Currently, I am trying to assign the atomtypes in charmm27 for the
polyethyleneimine polymer. It includes several different groups of atoms. I
included following illustration and asignment:
##############################################
                         H                     CH2
                         |                     /
NH2--CH2--CH2--N--CH2--CH2--N--CH2 ...

##############################################
I assigned and the charmm27 atomtypes as following and compared charmm36
atomtypes generated by CgenFF.
Atom       Charmm27     Charmm36
N (NH2) ---> NH2       |    NG321
N (NH1) ---> NH1       |    NG311
C (CH2) ---> CT2       |    CG321
H (HC2) ---> HA         |    HGA2
N                 ?           |    NG301

If you have any experience, please check my assignments the charmm27 atom
types and advice me the atomtype of the last Nitrogen, which were assigned
as NG301 with CgenFF.


Best Regards,

Mijiddorj