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

2015-06-17 Thread Justin Lemkul



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

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

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Re: [gmx-users] fractional charge

2013-12-16 Thread Justin Lemkul
On Mon, Dec 16, 2013 at 2:42 AM,  wrote:

> Dear gromacs users,
>
> I have run pdb2gmx for dimer with one MG ion in each chain.
>
> 1) If I run without Mg the total charge is -8.00 (-4.00 in each chain)
> 2) If I run with Mg the total charge becomes :
>
> a) -4.00 for A chain and +2.00 for Mg in A chain, total -2.00
> b) -4.129 for B chain and +2.00 for Mg in B chain, total -2.129
>
> Why does this fractional charge arise? I checked the PDB and found no
> covalent bond with Mg in any of the chains.
>
> 3) Then I removed Mg from B chain and found:
>
> a) -4.00(a chain) + 2.00 (Mg of A)
> b) -4.129(b chain)
>
> Please suggest.
>
>
You probably have missing atoms or are incorrectly choosing protonation
states for termini, but since you haven't shown us your command or the
screen output indicating your selections and any warnings from pdb2gmx, it
is hard to say.

-Justin

-- 

==

Justin A. Lemkul, Ph.D.
Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 601
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalem...@outerbanks.umaryland.edu | (410) 706-7441


==
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