[AMBER] Is there a trick to fix a poor structural feature?

From: Jonathan Gough <jonathan.d.gough.gmail.com>
Date: Tue, 23 Apr 2013 14:47:19 -0400

I have a pdb (from an x-ray structure) that was missing several
"loops"(they are floppy therefore were very disordered in the crystals).
I used swisspdb viewer to add the residues back in but on a few of the
"connections" it was a stretch.

therefore leap warns me that

WARNING: There is a bond of 6.802961 angstroms between:
------- .R<SER 363>.A<C 10> and .R<ARG 364>.A<N 1>
WARNING: There is a bond of 3.723094 angstroms between:
------- .R<SER 990>.A<C 10> and .R<ARG 991>.A<N 1>
WARNING: There is a bond of 4.437505 angstroms between:
------- .R<ALA 1197>.A<C 9> and .R<VAL 1198>.A<N 1>

and (of course?) there aren't any improper torsion parameters and I get
more warnings.

the question is

1 - can I still use what I have and minimize (I think I have tried this
several different ways and things go crazy)? If so any suggestions on how
to go about doing it? (I tried/thought I could do it in implicit and
explicit solvent followed by slow heating with heavy constraints and short
times steps.)

2 - is there a "trick" to fixing what I have?

3 - is there a better (easier) way to build out missing residues denovo
(letting amber build them by leaving out the residues does not work as it
fills in the missing atoms in a straight line - not in a loop as I need)

any insight or pointing in the right direction would be appreciated.

Thanks,
JOnathan
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Received on Tue Apr 23 2013 - 12:00:02 PDT
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