Hi Gourav,
        For standard residues like HOH, the atoms have to have their PDB standard names.  The names for the hydrogens in water are H1 and H2, not H.  The easiest way to correct these bad hydrogen names is just to delete all the hydrogens in the structure and let Chimera add them back with their correct names as a standard part of the minimization procedure.  You can delete all hydrogens in your structure with the command (Favorites→Command Line) "del H".

--Eric

        Eric Pettersen
        UCSF Computer Graphics Lab


> On Sep 11, 2023, at 11:29 PM, Gourav Das via Chimera-users <chimera-users@cgl.ucsf.edu> wrote:
>
> Dear all,
>
> I am trying to minimize the crystal structure of a protein using Chimera. But the program could not minimize the water molecules of the protein. I added hydrogen atoms to the whole structure. But during the minimization, it is showing the following error:
> No MMTK name for atom "H" in standard residue "HOH"
>
> It would be very helpful for me if you can suggest what changes I should make.
>
> Thank you!
>
> Sincerely
> Gourav Das
> Research Scholar
> Department of Chemistry
> IIT Kharagpur
> India
>
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