Set pH and salt concentration


I wonder if we can set the “pH” of the system by chosing the appropriate protonated state of the protein to be prepared by MDweb2 and also the salt concentration to 100 mM of salt once the protein is solvated.
In the manual, protpKa is mentioned, but I did not find how I can use this option this through MDweb2.

I want to thank the developers of this nice and intuitive molecular dynamic tool.


yes, there is a way to set the “pH” of the system, but is not available from the pre-configured workflows. You will need to prepare your own workflow step by step. The operation you are looking for is named “Set ionization state” and is available from a topology input. For example you can first run a “Generate topology for Amber” operation from your input PDB, and then run the “Set ionization state” modifying the input pH of the system (see attached image). You can also choose from two different methods here: propka (approximate) or CMIP (rigorous). Same happens with the salt concentration, which can be modified when solvating with the operation named “Solvate structure” (see image).

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