We have been trying to use OPC water model in our simulations. It looks like the order of loading water and macromolecule forcefields is important. Since ff19SB loads parm10, it will overwrite parameters for OW from tip3p, but not EP. This leads to abnormal behavior of water molecules which act as if they are positionally restrained. We have tested this with OL3 and OL15 as well. The pictures below show coordinates of two water molecules across a 50-ns trajectory with the aforementioned order of loading forcefields:
source leaprc.water.opc
source leaprc.protein.ff19SB
source leaprc.protein.ff19SB
source leaprc.water.opc
I wonder in case of other 3-point water models, tip3p could be overwriting SPC parameters and while it might diffuse properly, the actual values may not be correct.
Any ideas if this should be included as a warning in tleap or some other way of preventing it?
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Received on Wed Apr 14 2021 - 10:30:03 PDT
