VMD-L Mailing List

From: Chitrak Gupta (chgupta_at_mix.wvu.edu)
Date: Wed Sep 02 2015 - 11:05:47 CDT

Hi!

I am new to the FFTK plugin. I have followed the steps of the tutorial
video to generate the initial psf file (and that has all the information).
However, when I use it to generate the initial par file, none of the
bond/angles etc are defined. It is essentially an empty file. I am
copy-pasting the part of the par file below.

I also have an additional question. I am trying to parameterize an
unnatural amino acid. To make the molecule "complete", I have a -COOH as
the backbone carbonyl, I have two HN atoms attached to the backbone N, etc.
Would these make the parameterization inaccurate?

Here is my initial par file

BONDS
!V(bond) = Kb(b - b0)**2
!
!Kb: kcal/mole/A**2
!b0: A
!
!atom type Kb b0
!

ANGLES
!
!V(angle) = Ktheta(Theta - Theta0)**2
!
!V(Urey-Bradley) = Kub(S - S0)**2
!
!Ktheta: kcal/mole/rad**2
!Theta0: degrees
!Kub: kcal/mole/A**2 (Urey-Bradley)
!S0: A
!
!atom types Ktheta Theta0 Kub S0
!
!

DIHEDRALS
!
!V(dihedral) = Kchi(1 + cos(n(chi) - delta))
!
!Kchi: kcal/mole
!n: multiplicity
!delta: degrees
!
!atom types Kchi n delta
!

IMPROPER
!
!V(improper) = Kpsi(psi - psi0)**2
!
!Kpsi: kcal/mole/rad**2
!psi0: degrees
!note that the second column of numbers (0) is ignored
!
!atom types Kpsi psi0
!

NONBONDED nbxmod 5 atom cdiel shift vatom vdistance vswitch -
cutnb 14.0 ctofnb 12.0 ctonnb 10.0 eps 1.0 e14fac 1.0 wmin 1.5
!
!V(Lennard-Jones) = Eps,i,j[(Rmin,i,j/ri,j)**12 - 2(Rmin,i,j/ri,j)**6]
!
!epsilon: kcal/mole, Eps,i,j = sqrt(eps,i * eps,j)
!Rmin/2: A, Rmin,i,j = Rmin/2,i + Rmin/2,j
!
!atom ignored epsilon Rmin/2 ignored eps,1-4 Rmin/2,1-4
!

END

Regards,
Chitrak.