[gmx-users] Topology- make bonds with certain cut-off distance

2012-08-25 Thread mohan maruthi sena
Hi all,
   I want build a toplogy for a protein , for which , each and
every atom  has to  make bonds with other atoms with in certain
specified cut-off distance. How can i do this ?

Please suggest me a way,


Thanks in advance,
Mohan
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Re: [gmx-users] Topology- make bonds with certain cut-off distance

2012-08-25 Thread Erik Marklund
Hi,

In case you want the bonds to be dynamic I think the only way is to use 
tabulated interactions. A bit tedious to set up, but doable. Note that this 
will NOT emulate angles or dihedrals, just the stretching term. I can't 
understand why you would want bonds between all atoms within a certain 
distance, however, and I hope you know what you're doing.

Erik
 
25 aug 2012 kl. 06.54 skrev mohan maruthi sena:

 Hi all,
   I want build a toplogy for a protein , for which , each and
 every atom  has to  make bonds with other atoms with in certain
 specified cut-off distance. How can i do this ?
 
 Please suggest me a way,
 
 
 Thanks in advance,
 Mohan
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---
Erik Marklund, PhD
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,75124 Uppsala, Sweden
phone:+46 18 471 6688fax: +46 18 511 755
er...@xray.bmc.uu.se
http://www2.icm.uu.se/molbio/elflab/index.html

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Re: [gmx-users] Topology- make bonds with certain cut-off distance

2012-08-25 Thread mohan maruthi sena
Hi ,
 Thanks for your reply.  I actually want to build an elastic
network model (ENM) for Protein containing 372 residues. According to
literature, ENM model only considers C-alpha atoms of protein and
discards rest of the atoms.The potential only considers bonded term
only. It does not
contain angle,dihedral or non-bonded term.  To build an ENM model the
specified atom makes bond with all other atoms with certain cutoff
distance. I consider the distance between two c-alpha atoms is 0.38nm
and force constant of 69.1 kj/(nm)2.I have written a code which gives
the number of  atoms around a particular atom with in certain cut-off
distance, With this i will know what are the atoms that are needed to
connect a particular atom.I have generated .gro and .top files using
pdb2gmx command .  After generating topology file , I replace bonds
section with the  connectivity information i get from code. The next
steps are equilibration and production. I am not sure whether it takes
connectivity information from topology or not. If it is not then how
can i mention it forms bonds with in certain distance . Finally , if i
run the simulation with all the above mentioned steps  and load the
trajectory in vmd , the protien gets contracted after first step.

Thanks,
Mohan

On Sat, Aug 25, 2012 at 3:43 PM, Erik Marklund er...@xray.bmc.uu.se wrote:
 Hi,

 In case you want the bonds to be dynamic I think the only way is to use 
 tabulated interactions. A bit tedious to set up, but doable. Note that this 
 will NOT emulate angles or dihedrals, just the stretching term. I can't 
 understand why you would want bonds between all atoms within a certain 
 distance, however, and I hope you know what you're doing.

 Erik

 25 aug 2012 kl. 06.54 skrev mohan maruthi sena:

 Hi all,
   I want build a toplogy for a protein , for which , each and
 every atom  has to  make bonds with other atoms with in certain
 specified cut-off distance. How can i do this ?

 Please suggest me a way,


 Thanks in advance,
 Mohan
 --
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 ---
 Erik Marklund, PhD
 Dept. of Cell and Molecular Biology, Uppsala University.
 Husargatan 3, Box 596,75124 Uppsala, Sweden
 phone:+46 18 471 6688fax: +46 18 511 755
 er...@xray.bmc.uu.se
 http://www2.icm.uu.se/molbio/elflab/index.html

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