[Chimera-users] AutoDock Vina error on Chimera

[Elaine Meng]

Hello Utkarsh,
Autodock Vina only works with the usual common elements.  Those messages from Autodock Vina are saying that it does not recognize atom types Ho (holmium??) and Hc (which is not even an element symbol).  Without your providing an example input that shows the problem, my only guess is that you have hydrogens with 4-character atom names that start with HO and HC which makes Autodock scripts guess that they are different elements (instead of hydrogen).   I don't know if Chimera added those hydrogens or if they were already in your ligand files when you opened them.

Autodock Vina is developed by another group and and so we are not experts in that program.  However, my understanding is that it doesn't use atomic charges and doesn't use hydrogens on carbons.  So you may not need to use Dock Prep at all, because the Autodock Vina tool already has an option to add hydrogens in Chimera (see the "Receptor options" in the tool).  
<https://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/vina/vina.html>

However, you could turn off that option in the Autodock Vina tool if you wanted just to run addh separately beforehand.  That would also allow you to delete the nonpolar ( = those on carbon) hydrogens before using Autodock Vina, e.g. command

delete HC

...which should get rid of the "Hc" type messages.  You don't want to delete the hydrogens on oxygen even though it would prevent "Ho" messages, since they are needed for atom type identification.  Instead you would have to either manually edit your ligand atom names to avoid 4-character hydrogen names starting with HO (if my theory that 4-character atom names are the problem is correct).

Please note that the Autodock Vina tool in Chimera is of limited use, as mentioned in the gray box at the top of the help page:

"this tool only allows docking a single ligand with very limited sampling. For a more intensive sampling of space, as needed for most research applications, or access to other options such as ligand database search, we recommend running the locally installed copy of AutoDock Vina directly (not using Chimera)."

I hope this helps,
Elaine

> On Jun 24, 2022, at 3:28 AM, Utkarsh Narsaria via Chimera-users <chimera-users at cgl.ucsf.edu> wrote:
> 
> Dear Team,
> I am using chimera for a typical protein-ligand docking study. The ligands were prepared in chimera itself using the dockprep options using gasteiger charges and amber ff14SB force field. While docking the same using AutoDock Vina function in Chimera , we encountered few errors for some of the ligands. The errors are explained as follows : 
> 1. "" Ho" is not a valid dock type AutoDock atom types are case-sensitive."
> 2. Autodock Vina Error on Chimera: "ValueError: Could not find an atomic number for Hc Hc" 
> Any inputs regarding these will be helpful in resolving the issues.
> Regards,
> Utkarsh