[gmx-users] free energy : query on constraint force pull code

[Sanku M]

Hi,
  I would like to use constraint force pull code to calculate the free energy of association of two peptide  using the distance between center of mass of two peptides as reaction coordinate. I am planning to use gromacs 4. 
Here I have some queries:
1. Since I will constraint method, I guess,  I do not have to use any force-constant ( unlike umbrella sampling) . If that is correct, do I need to specify a pulling rate ? If so, what will be a typically appropriate range of value to start with ?

2. In umbrella sampling technique, we check the overlap of position histogram of two consecutive windows to check the convergence . Here , using constraint force technique, what should I check for convergence. Is that the force ?

3. Once I get time series of force for all windows, how  should I unbias the effect of constraint and what formula I should use to integrate the force? Is that integration implemented in gromacs ?

Thanks
Sanku


      
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