[gmx-users] Resplica exchange with solute tempering (REST)

[Sai Pooja]

Hi,

I have tried to implement a variant of Replica exchange called REST using
gromacs. In REST, the potential energy is scaled in the following manner:

For the nth replica:

E_n = E_protein-protein + a_n * E_protein-water + b_n * E_water-water

I used tables to implement this. Separate tables for the three components
were generated with the corresponding scaled potentials. Then for replica
exchange I use gromacs to run MD for 1ps then extract the Energy
corresponding to the three components using g-energy and exchange replicas
based on the acceptance criteria outlined in the paper.

E_water-water = LJ_water-water + Coulomb_water-water
E_protein-water = LJ_protein-water + Coulomb_protein-water
E_protein-protein = Potential - E_protein-protein - E_protein-water

Is there some obvious error in this implementation? I use CHARMM forcefield
with tip3p water and alanine dipeptide. The paper uses OPLS-AA with tip4p
and is able to use 3 replicas -300k, 420k, 600k. I am not able to reproduce
these results i.e. the same acceptance ratio with 3 replicas. 5 replicas
gives something close to the desired acceptance ratio.

Pooja




-- 
Quaerendo Invenietis-Seek and you shall discover.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://maillist.sys.kth.se/pipermail/gromacs.org_gmx-users/attachments/20110328/adf44a50/attachment.html>