[gmx-users] Fractional charge for protein after topology preparation

Justin Lemkul jalemkul at vt.edu
Thu Jun 18 01:52:10 CEST 2015



On 6/17/15 7:49 PM, Agnivo Gosai wrote:
> Dear Users
>
> I wanted to prepare the topology file for a particular protein system using
> AMBER99SB through pdb2gmx, however I received numerous warnings and the
> command crashed.
>
> Hence I used the -missing tag with pdb2gmx to have a look at all the
> warnings generated.
> Typical warnings are given below :
>
> 1) WARNING: there were 0 atoms with zero occupancy and 8 atoms with
>           occupancy unequal to one (out of 2569 atoms). Check your pdb file.
>
> 2) Warning: Long Bond (15-17 = 0.42516 nm)
> Warning: Long Bond (15-17 = 0.42516 nm)
>
> ( above 30 such messages)
>
> 3)WARNING: atom CG is missing in residue GLN 17 in the pdb file
>
>
> WARNING: atom HG1 is missing in residue GLN 17 in the pdb file
>           You might need to add atom HG1 to the hydrogen database of
> building block GLN
>           in the file aminoacids.hdb (see the manual)
>
>
> WARNING: atom HG2 is missing in residue GLN 17 in the pdb file
>           You might need to add atom HG2 to the hydrogen database of
> building block GLN
>           in the file aminoacids.hdb (see the manual)
>
>
> WARNING: atom CD is missing in residue GLN 17 in the pdb file
>
>
> WARNING: atom OE1 is missing in residue GLN 17 in the pdb file
>
>
> WARNING: atom NE2 is missing in residue GLN 17 in the pdb file
>
>
> WARNING: atom HE21 is missing in residue GLN 17 in the pdb file
>           You might need to add atom HE21 to the hydrogen database of
> building block GLN
>           in the file aminoacids.hdb (see the manual)
>
> (Numerous !!)
>
> 4) WARNING: WARNING: Residue 2 named GLN of a molecule in the input file
> was mapped
> to an entry in the topology database, but the atom CD used in
> an interaction of type improper in that entry is not found in the
> input file. Perhaps your atom and/or residue naming needs to be
> fixed.
>
>
>
> WARNING: WARNING: Residue 8 named GLU of a molecule in the input file was
> mapped
> to an entry in the topology database, but the atom CG used in
> an interaction of type improper in that entry is not found in the
> input file. Perhaps your atom and/or residue naming needs to be
> fixed.
>
>
>
> WARNING: WARNING: Residue 25 named ARG of a molecule in the input file was
> mapped
> to an entry in the topology database, but the atom NE used in
> an interaction of type improper in that entry is not found in the
> input file. Perhaps your atom and/or residue naming needs to be
> fixed.
>   ( Again Numerous !!)
>
> And lastly I get a fractional charge for the protein !!
>
> Before cleaning: 6012 dihedrals
> Keeping all generated dihedrals
> Making cmap torsions...There are 6012 dihedrals,  434 impropers, 4106 angles
>            5949 pairs,     2280 bonds and     0 virtual sites
> Total mass 15942.450 a.m.u.
> Total charge 3.336 e
> Writing topology
>
> -------------------------------------------------------------------------------------------------------------------------
>
> I looked at similar issues in the forum and I think that the PDB file I use
> is corrupted and is a reason why I am getting "missing residue" warnings (
> in sl. no. 3 and 4 of my mail).
>

Look for MISSING lines in the PDB header; this will tell you about what isn't 
there when collecting the diffraction data.

> However I am unable to understand the fractional charge for the protein.
> Any suggestions ???
>

If you're missing atoms, and those atoms normally carry charge to confer certain 
properties to the residues...

-Justin

-- 
==================================================

Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

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


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