[Biopython] Best way to change the chain identifiers of a set of residues
Claudia Millán Nebot
cmncri at ibmb.csic.es
Thu Nov 26 10:59:02 UTC 2015
Hi Jordan, the removal of the residues is working, is the renaming of the
chains that is causing trouble. I attach an example of input/output
produced by the function.
2015-11-26 9:09 GMT+00:00 Jordan Willis <jwillis0720 at gmail.com>:
> Also, the detach_child method should work in place, so I’m not sure why
> this is not working. Can you give an example PDB?
>
> Jordan
>
> On Nov 25, 2015, at 12:16 PM, Claudia Millán Nebot <cmncri at ibmb.csic.es>
> wrote:
>
> Dear all,
>
> I am writing a function that examines a structure, and if there are
> discontinuous regions that are smaller than a certain size, they will be
> removed from the structure. Then, I would like to write the structure as a
> pdb in which the chain identifiers are different for each discontinuous
> fragment. For that purpose, I want to change the chain id of certain
> residues. ¿What will be the best way to do it? Because right now it is not
> working, of course, because I am iterating over something that I am trying
> to change at the same time. Maybe I am missing something very obvious or
> straightforward, but I do not see what will be the best way to do it...
> ¿Maybe creating and empty chain and using the set_parent method?
>
> The current code looks like this:
> def trimByContinuityLimit(pdb_file,min_size):
> parser=PDBParser()
> structure=parser.get_structure(pdb_file[:-4],pdb_file)
> residues=Selection.unfold_entities(structure,'R')
>
> list_id="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890"
> dictio_chainid={}
> residues_to_remove=[]
> current_listres=[]
> index=0
> for i in range(len(residues)-1):
> res1=residues[i]
> res2=residues[i+1]
> id1=res1.id
> id2=res2.id
> check=Bioinformatics.checkContinuity(res1,res2)
> #print 'check',check
> #print 'list_id[index]',list_id[index]
> if check==True:
> #print "These two residues are consecutive",res1,res2
> if id1 not in current_listres:
> current_listres.append(id1)
> dictio_chainid[id1]=list_id[index]
> if id2 not in current_listres:
> current_listres.append(id2)
> dictio_chainid[id2]=list_id[index]
> #print 'list_id[index]',list_id[index]
> #print 'id1,dictio_chainid[id1]',dictio_chainid[id1],id1
> #print 'id2,dictio_chainid[id2]',dictio_chainid[id2],id2
> elif check==False:
> #print "These two residues are not consecutive",res1,res2
> if id1 not in current_listres:
> current_listres.append(id1)
> dictio_chainid[id1]=list_id[index]
> if len(current_listres)<min_size:
> residues_to_remove.extend(current_listres)
> if i==len(residues)-2 and min_size>1: # If we reach this
> point, then the last residue is not continuous so it is single :
> residues_to_remove.append(id2)
> else:
> current_listres=[]
> current_listres.append(id2)
> index=index+1
> dictio_chainid[id2]=list_id[index]
> # Remove the residues and write the pdb
> for model in structure:
> for chain in model:
> for residue in chain:
> id_res=residue.id
> if id_res in residues_to_remove:
> chain.detach_child(id_res)
> else:
> chain.id=dictio_chainid[id_res]
> io=PDBIO()
> io.set_structure(structure)
> io.save(pdb_file[:-4]+'_trimmed.pdb',write_end=False)
>
> Thanks in advance :)
>
> Claudia
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>
>
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