Hello Santhosh--

> 
> I want to refine a protein against RDC's and have been following the scripts 
> in
> gb3_rdc and other examples. The protocol I followed is very similar to the
> protocol given in the scripts but just to check a few things, I have not done 
> any
> minimization in the catesian space but only in the torsional space. I observe
> that there are peptide bond planarity violations (omega torsional angle) in
> that. 
> 
> That is odd as I thought IVM only uses phi and psi only as coordinates. The
> starting structure does not have any omega angle discrepancies. But the 
> refined
> structures have it. Can you please let me know where should I be looking for 
> the
> possible cause of error? 

By default, all torsion angles are allowed to move. In more modern
scripts, you can make omega rigid by passing the fixedOmega=True
argument to protocol.torsionTopology. In the old scripts in gb3_rdc,
you should call the function

selectTools.IVM_groupRigidBackbone(dyn)

before the call to

dyn.autoTorsion()

Now, normally, you should not have significant omega violations- that
points to something else amiss.

Charles

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