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[ccp4bb] torsion restraints and phi/psi |
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CCP4bb navigationCCP4bb <-- 2007 <-- November 2007 <-- 07 November 2007Subject: torsion restraints and phi/psi From: Bernhard Rupp bernhardrupp {- at -} SBCGLOBAL {- dot -} NET Date: 2007-11-07 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 ----------------------------------------------------------------- Bernhard Rupp 001 (925) 209-7429 +43 (676) 571-0536 br@qedlife.com bernhardrupp@sbcglobal.net http://www.ruppweb.org/ ----------------------------------------------------------------- The hard part about playing chicken is to know when to flinch ----------------------------------------------------------------- CCP4bb navigationCCP4bb <-- 2007 <-- November 2007 <-- 07 November 2007 |
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