<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div>Hi,</div><div> I have a system containing water and a large protein. In the simulation, I do not want the protein center of mass to drift away. I was wondering what will be the reasonable method in gromacs to fix the position of the center of mass of the protein in its original position . I was thinking about two options in gromacs.</div><div> 1) use the protein as comm-grp only to remove its center of mass motion . ( or should I use both protein and non-protein ( water) center of mass as comm-grps separately ).</div><div> 2) Finding the residue closest to center of mass of the protein ( but I am not sure how to do it ).</div><div>Can anyone suggest which will be a good idea ?</div><div><br></div><div>Sanku</div></div></body></html>