Hi there,
I’m running a 500ns MD simulation of 8 peptide-protein systems using GROMACS 2023 to investigate viral-host peptide-protein interaction. My protein (86 residues) is the same for all 8 systems, my peptides (8 residues) are different for each system, and each peptide-protein complex is solvated with TIP3P (no membranes or any other components included). I prepared all of my systems using CHARMM-GUI. I have the complete 500ns simulations for all of my systems. My first issue was re-wrapping and re-centering my peptide-protein complex - I’ve read many posts from different forums on how to re-wrap and re-center protein-protein systems, especially when the chains split, causing several spikes/jumps in the RMSD/Radius of Gyration graphs. Thanks to those posts, I've managed to fix this issue for 6 of my 8 systems using the following “gmx trjconv” commands:
- gmx trjconv -s md.tpr -f md.xtc -o md.whole.xtc -pbc whole
- gmx trjconv -s md.tpr -f md.whole.xtc -o md.whole.nojump.xtc -pbc nojump
- gmx trjconv -s md.tpr -f md.whole.nojump.xtc -o md.whole.nojump.mol.xtc -pbc mol -center -ur compact
- gmx trjconv -s md.tpr -f md.whole.nojump.mol.xtc -o md_fit.xtc -fit rot+trans
However, for 2 of my systems, the spikes in RMSD/Rg graphs are still there, even after using these gmx trjconv commands. Can someone please advise which gmx trjconv options (and in which order) are usually best for re-wrapping and re-centering the trajectories of peptide-protein complexes? Am I missing something with the gmx trjconv options I’m using, or maybe I’m using some of the options incorrectly? I’ve tried several combinations of the options shown in the GROMACS2023 manual, but none of them seem to really "work" in the sense that I don’t get those spikes/jumps in RMSD/Rg graphs. I’ve also seen several forums speak about chains splitting due to periodic boundary conditions (PBCs), which is what I believe I managed to fix with the above commands. Please see an example of the system and what I mean by “spikes/jumps” in Rg (left), and a system where I “fixed” the spikes (right) with the above commands. Apologies for the long description. I’d really appreciate any help - I’m kind of at my wit’s end …
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