[ccp4bb] torsion restraints and phi/psi

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

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Subject: torsion restraints and phi/psi
From: Bernhard Rupp bernhardrupp {- at -} SBCGLOBAL {- dot -} NET
Date: 2007-11-07

Dear All,

I wonder about the exact use of torsion restrains and the effect
on phi/psi/w validation.

I think in refmac, omega is restrained with a 1-4 dihedral or
planarity, cis when the proper LINK statement is invoked - no
questions there.

In literature I find remarks like 'usually not restrained' as far
as phi/psi goes. This is not irrelevant because the phi-psi
angles are crossvalidation for the otherwise restrained
geometry. So questions arise.

a) does refmac restrain phipsi at all (except vdw repulsion
which does not bias them otherwise)?

b) do other programs restrain or not phipsi?

c) In particular, what does torsion angle refinement do to
the validity of phipsi crossvalidation?

I vaguely recall statements such as 'robust even against strong
empirical potentials' in the context of SA/TA/EREF refinement...
but don't find the ref anymore im my piles.

Best regards, br
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Bernhard Rupp
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CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Postdoctoral Fellowship - Porto, Portugal
From: Pedro Pereira ppereira {- at -} IBMC {- dot -} UP {- dot -} PT
Date: 2007-11-07

Next message:
Subject: Re: elusive DNA density
From: price {- at -} UCHICAGO {- dot -} EDU price {- at -} UCHICAGO {- dot -} EDU
Date: 2007-11-07