On 5/25/12 5:43 PM, Steven Neumann wrote:
Dear Gmx Users,

My surface is made of 4 types of residues created on my own. They are placed
within they vdwradii away from each other. I want to keep the surface rigid and
allow it to move into only one direction (freezgrps, freezdim). Each residue is
made of one atom. The best option would be to create bonds between or apply
distnce restraints e.g. using cutoff of 1nm.

How can I create bonds between them? Shall I specify in my aminoacids.rtp the
possibilities of each of them to create bonds with any 3 others? Then to add
proper lines to specbond.dat?
I want two of them to create extra bond with my protein terminals. How to do
this using bonds? Or would you suggest distance restraints?


The nature of the model depends on how you want to treat them. Distance restraints are harmonic potentials that can be set up with arbitrary flexibility. Bonds can be harmonic or rigid, depending on the use of constraints. The manner that makes the most sense for what you hope to achieve should prevail.

As for creating the topology, you can only use pdb2gmx to create a linear sequence of bonded residues. Thus, you can't specify all possible bonds within the .rtp file; the majority of the work comes in creating suitable entries in specbond.dat. There are a number of discussions in the list archive about doing so, usually in the context of silica-type species.

-Justin

--
========================================

Justin A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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