[Chimera-users] classifying contact interactions
mohammad.shahid at gmail.com
Thu Oct 29 04:10:31 PDT 2009
Thanks a lot for suggestion of using an alternate way of classifying the
I am currently using it with step by step selection of different types. And
its working great!!! thanks again.
Could you please also give me some hints on the other way you mentioned in
(d) below in conversation?
On Mon, Oct 26, 2009 at 9:02 PM, Elaine Meng <meng at cgl.ucsf.edu> wrote:
> Just some additions to what Eric said...
> (a) you would probably want to use "aromatic ring" instead of "aromatic" --
> "aromatic" specifies entire aromatic amino acids, "aromatic ring" specifies
> aromatic rings in all kinds of molecules. In Eric's example, the ligand
> residue name was LIG ... so of course, if it has some other name you would
> use that instead.
> (b) you could select most (but not all) charged groups based on atom type,
> for example with the command:
> select Ng+ | N3+ | N2+ | O2- | O3-
> That gets atom types in charged groups commonly found in amino acids and
> nucleotides, except histidines. To include histidines, but only the ones
> that are charged, you would need to add hydrogens (AddH tool or command
> addh), add charge (Add Charge tool or command addcharge), and then use
> select Ng+ | N3+ | N2+ | O2- | O3- | :/amberName=HIP & @nd1,ne2
> (The charge assignment process identifies which histidines are doubly
> protonated and assigns them the AMBER residue name HIP.)
> A limitation of using this atom type approach is that we do not have
> thiolate sulfur atom type; if there is specific Cys thiolate you wish to
> consider, you would have to add that sulfur to the selection manually.
> There are additional atom types for charged functional groups, but they
> would not occur in proteins. If manmade ligands are involved, however, you
> may want to take a look at the list of atom types and possibly add
> N1+,P3+,S3+,S3- (no, that's not thiolate even though it
> sounds like it) to the selection command.
> Here is an earlier posting about finding salt bridges:
> (c) I wasn't sure if you were also interested in ion-aromatic (cation-pi)
> interactions. Here some example commands for looking at possible cation-pi
> sel aromatic ring | N1+ | N2+ | N3+ | Ng+ | :/amberName=HIP & nd1,ne2
> del ~ sel
> sel aromatic ring
> findclash sel overlap -1 hbond 0 log true
> (d) yet another approach is to just get all the contacts of all types and
> filter them afterwards. However, that would require you to figure out the
> types of interactions based on the residue and atom names, which might be a
> lot of work. If using this approach, you might want to remove all the
> hydrogens first, since they would generally provide a large amount of
> redundant information.
> I hope this helps,
> On Oct 26, 2009, at 12:06 PM, Eric Pettersen wrote:
> Hi Shahid,
>> It certainly would be easier if Chimera allowed you to find
>> contacts/H-bonds between two arbitrary sets of atoms rather than between one
>> set and "everything else". I will open a feature-request ticket in our Trac
>> database for this with you on the recipient list so you will know when it
>> gets implemented. It will probably be several months before I have time to
>> get to it.
>> In the interim there is an uglier method for getting what you want
>> -- at least for contacts. Basically you delete away all the atoms you don't
>> care about. So to find the aromatic contacts between ligand and non-ligand
>> do this (Favorites->Command Line):
>> del ~aromatic
>> sel :LIG
>> then find contacts between selected atoms and all other atoms. You would
>> have to open a new copy of your system (and close the mutilated one!) to
>> find other interactions.
>> To get charge interactions first add charges to your atoms with the
>> Add Charge tool. You can then select ligand atoms with more than a certain
>> negative charge and non-ligand with more than a certain positive charge (say
>> .1 for this example) with:
>> sel :LIG & @/charge<-0.1 | ~:LIG & @/charge>0.1
>> then delete all other atoms with:
>> del ~sel
>> then find clashes as above. Then on a new copy of the system find
>> contacts between atoms with the charges reversed.
>> Like I said: ugly!
>> Eric Pettersen
>> UCSF Computer Graphics Lab
>> On Oct 24, 2009, at 8:00 AM, M. Shahid wrote:
>> Dear All,
>>> I have a question regarding the contact interactions between a
>>> protein-ligand complex.
>>> I can retrieve the contacts by the findclash command in --nogui mode as
>>> chimera --nogui protligcomplex.pdb clash.com
>>> and similarly I can find the hbonds.
>>> The output I am getting is as below:
>>> 32 contacts
>>> atom1 atom2 overlap distance
>>> LIG 1 H ALA 265.A O 1.045 1.435
>>> LIG 1 O ALA 265.A O 0.550 2.430
>>> LIG 1 N GLU 169.A OE2 0.439 2.666
>>> LIG 1 H GLU 169.A CD 0.116 2.584
>>> LIG 1 O ASN 253.A 1HD2 0.094 2.386
>>> LIG 1 H ALA 265.A C 0.090 2.610
>>> LIG 1 C ALA 265.A O 0.059 3.121
>>> LIG 1 N ASN 253.A OD1 -0.037 3.142
>>> LIG 1 C ALA 265.A O -0.039 3.219
>>> LIG 1 N GLU 169.A HG3 -0.072 2.697
>>> LIG 1 C PHE 168.A HB2 -0.081 2.781
>>> LIG 1 N GLU 169.A CG -0.113 3.438
>>> LIG 1 N GLU 169.A CD -0.125 3.450
>>> LIG 1 N GLU 169.A CD -0.128 3.453
>>> LIG 1 C MET 270.A HG2 -0.140 2.840
>>> LIG 1 N PHE 168.A CD2 -0.163 3.488
>>> .......... .... ... .. .
>>> Now I want to further classify these contact interactions into more other
>>> Aromatic and Ionic (anion < - > cation).
>>> Is there any way in Chimera to achieve this?
>>> Or if I want to do it with some scripting, which atoms I would say are
>>> involved in ionic
>>> and aromatic interactions considering the distance value as well?
>>> I would be very much grateful if someone suggest me a way to do this.
>>> Best regards,
>> Chimera-users mailing list
>> Chimera-users at cgl.ucsf.edu
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