Re: [ccp4bb] Summary - Valid to stop Refmac after TLS refinement?

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Subject: Strange behavior in R32
From: dklein {- at -} FHCRC {- dot -} ORG dklein {- at -} FHCRC {- dot -} ORG
Date: 2007-04-04

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Subject: Re: Strange behavior in R32
From: Bart Hazes bart {- dot -} hazes {- at -} UALBERTA {- dot -} CA
Date: 2007-04-04

Subject: Re: Summary - Valid to stop Refmac after TLS refinement?
From: Bernhard Rupp bernhardrupp {- at -} SBCGLOBAL {- dot -} NET
Date: 2007-04-04

>People also felt that the RMSD bond/angle of 0.016/1.6 was still a little
high.

This was subject of a discussion before on the board and I still don't
understand it:

If I recall correctly, even in highly accurate and precise
small molecule structures, the rmsd of corresponding
bonds and angles are ~0.014A and 1.8deg.

It always seems to me that getting these values much below is not a sign
of crystallographic prowess but over-restraining them?

Is it just that - given good resolution in the first place - the balance
of restraints (matrix weight) vs low R (i.e., Xray data) gives the best
Rfree or lowest gap at (artificially?) lower rmsd?

Is that then the best model?

I understand that even thermal vibration accounts for about 1.7 deg
angle deviation - are lower rmsd deviations then a manifestation
of low temp? But that does not seem to be much of an effect, if
one looks at the tables from the CSD small mol data (shown in
nicely in comparison to the 91 Engh/Huber data in Tables F, pp385).

Thx, br

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CCP4bb <-- 2007 <-- April 2007 <-- 04 April 2007

Previous message:
Subject: Strange behavior in R32
From: dklein {- at -} FHCRC {- dot -} ORG dklein {- at -} FHCRC {- dot -} ORG
Date: 2007-04-04

Next message:
Subject: Re: Strange behavior in R32
From: Bart Hazes bart {- dot -} hazes {- at -} UALBERTA {- dot -} CA
Date: 2007-04-04