Peter C. Lai wrote:
Should I couple a ligand associated with a membrane protein to the same
COM group as the Protein_POPC group? It makes sense to me that would be the case since if we are investigating the interaction between protein+membrane and ligand we want to have the same COM correction vector applied to both relative to SOL_Ions but I just wanted to make sure...


If specifying multiple groups for COM motion removal, yes, the intuitive solution is to group the ligand with the protein (since they're physically bound, presumably). The general complication is whether or not multiple COM groups are necessary - if the protein protrudes out into the solvent in any substantial way, you could have instability when the solvent and protein/membrane COMs get re-set. I have seen this before in the case of a protein in water with separate COM groups (which is not appropriate, for the record). Membrane systems are somewhat more complicated because they form interfaces that can slide, but if the protein somehow affects this behavior, well, I don't know that there's a trivial solution other than "comm_grps = System" to avoid possible instability. If you're interested in diffusion-related properties, on the other hand, that may not be appropriate. Plenty to think about, but again, probably no "easy" solution.

-Justin

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========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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