[gmx-developers] modify pdb2gmx and/or g_protonate in order to add specific hydrogen name

[Landry Charlier]

Thank you for yours answers.

I have already tried the solution of Dr. Abraham. Indeed for POPC I have:
- created a "clone" for POPC. Indeed, if i put the line "3 4 H13 C13 N  
C12" in the lipid.hdb file, pdb2gmx will bug by saying that the atom  
H131 is not in the residue POPC.
So i have created the residue POPD, a clone of POPC in the lipid.rtp  
but with changes for the hydrogen names.
- filled the lipid.hdb for the residue POPD
- done a script with the sed command the change the residue name (POPD  
to POPC) and the hydrogen names.

The problem is that I don't only work on POPC, I work on all the  
lipids contains in the charmm36. So I have to create a clone and a  
script for each lipid. Before doing all these steps, I have written  
this mail in order to know if there is an other solution.

I think that the better (but may be not the easier) solution is to  
change the code. I will try the trick of Emanuel and if it's not good,  
I will do all the clones and scripts.

Landraille







Mark Abraham <mark.j.abraham at gmail.com> a écrit :

> On Fri, Feb 1, 2013 at 7:40 PM, Emanuel Peter <
> Emanuel.Peter at chemie.uni-regensburg.de> wrote:
>
>> I would try in the hdb entry
>>
>> H12A C13 N C12
>> H13B C13 N C14
>> H13C C13 N C15
>>
>> or
>>
>> H12A C13 C12 C14
>> H13B C13 C12 C15
>> H13C C13 N C16
>>
>> and then afterwards minimize.....
>>
>> Others might know a better way.
>> This way was (for me) the easiest way.
>> After minimization I got a reasonable protonation.
>>
>
> Even if you can abuse pdb2gmx to put three hydrogens in like this, you
> still have to get lucky that EM can sort out the problems. If it's only a
> naming problem, it's much more reliable to rename the atoms...
>
> Best and good luck,
>>
>> Emanuel
>>
>> >>> Landry Charlier <landry.charlier at univ-montp1.fr> 02/01/13 12:51 AM >>>
>>
>>
>> Hello,
>>
>> I have some problems in order to automatically add hydrogen to lipids
>> with charmm36 force field. Indeed, when several hydrogen have to be
>> added to the same atom, the command pdb2gmx -ignh or g_protonate add
>> them with the same name but with the last number incremented by 1
>> thanks to the .hdb file.
>>
>> Example : for charmm36, the hydrogens added to the CB atom of ARG are
>> named HB1 & HB2 thanks to the line "2 6 HB CB CG CA" in the
>> aminoacids.hdb file.
>>
>> For lipids, the hydrogen names differ by a letter. H13A, H13B H13C are
>> linked to C13 in POPC in charmm36 for example.
>>
>> I would like to modify g_protonate or pdb2gmx in order to add hydrogen
>> with a specific name like that:
>> - If only 1 name is written in hdb file and several atoms have to be
>> added, the hydrogen names have been incremented by 1 as it's by
>> default (see the example of Arg above).
>> - If there are as many names as the number of hydrogen to add, pdb2gmx
>> and/or g_protonate will choose these names. The hdb file should be
>> like this : 3 4 H13A,H13B,H13C C13 N C12
>>
>> But I check the g_protonate and pdb2gmx files in the source code and I
>> am not enough good in programming for modify them.
>>
>> Could you help me please?
>>
>
> You've not been completely clear on why you need the atoms named
> differently, so I'll assume you need some output file from pdb2gmx to have
> atom names that match something else. If so, it is much easier to use sed
> three times to do the necessary changes than to think about touching C
> code. For example:
> sed -e 's/H131/H13A' infile > outfile
>
> Since you've got a script calling pdb2gmx anyway (hint, hint), you don't
> even have to remember the magic words once you write them!
>
> Mark
>