[gmx-users] SPC water model for CHARMM27FF

Justin Lemkul jalemkul at vt.edu
Sat Oct 28 20:27:28 CEST 2017

On 10/28/17 5:49 AM, Archana Sonawani-Jagtap wrote:
> Dear all,
> I have used SPC water model with CHARMM27 forcrfield for performing 100ns
> protein-DNA simulation instead of TIP3P. I wanted to know if SPC water
> model can affect my simulation results in anyway considering many charged
> residues.

Yes, it certainly is. CHARMM specifically balances water interactions 
assuming CHARMM-modified TIP3P (with LJ on H atoms) to target individual 
QM water interactions. If you change the water model, you potentially 
imbalance the entire force field. The water model should generally be 
viewed as an integral part of the force field, unless one does a 
complete validation that the change in water model does not negatively 
impact the target data (water interactions, hydration free energies, 
helix-coil equilibrium, etc).

CHARMM36 is also superior to CHARMM27 and I recommend you use it 
instead, particularly if you care about subtle aspects of the DNA structure.



Justin A. Lemkul, Ph.D.
Assistant Professor
Virginia Tech Department of Biochemistry

303 Engel Hall
340 West Campus Dr.
Blacksburg, VA 24061

jalemkul at vt.edu | (540) 231-3129


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