[gmx-users] How to calculate interaction energy between two groups for every frame in a trajectory?

[sunyeping]

Dear all, 

I am doing protein-DNA complex simulations with gromacs and I have gotten a trajectory. Now I want to calculate interaction energy between the protein and the DNA in every frame of the trajectory so that I can pick out a frame in which the  interaction energy between them is the largest, but I don't know how. I have used "enemat" , but it only gives a range of the energy, not every frame. The output read: 

Last energy frame read 5000 time 500000.000         
Will build energy half-matrix of 2 groups, 6 elements, over 5001 frames
Matrix of Coul-SR energy ranges from -18999.681641 to -1608.268188
Matrix of LJ-SR energy ranges from -2540.941650 to -675.151306
Matrix of total energy ranges from -21540.623047 to -2283.419434

So could you tell me how to calculate interaction energy between two groups for every frame in a trajectory?

Best regards.