>> If this is the case, why can't we use model B factors to validate our
>> structure? I know some people are skeptical about this approach because B
>> factors are refinable parameters.
>>
>> Rangana
>
> It is not clear to me exactly what you are asking.
>
> B factors _should_ be validated, precisely because they are refined parameters
> that are part of your model. Where have you seen skepticism?
Rangana said that B-values should not be used *to validate structures*, NOT
that B-values themselves shouldn't be validated themselves.
I suppose I am at least in part to blame for the former notion and the reason
for this (at least circa 1995 when the Angry Young Men from Uppsala first
starting harping on about this) was that B-values tend(ed) to be error sinks
which could "absorb" all sorts of errors and phenomena in addition to
modelling atomic displacement (e.g., unresolved disorder, unresolved NCS
differences, incorrect restraints, incorrect atom types modelled, partial
ocupancies, etc.).
--Gerard
******************************************************************
Gerard J. Kleywegt
http://xray.bmc.uu.se/gerard mailto:[log in to unmask]
******************************************************************
The opinions in this message are fictional. Any similarity
to actual opinions, living or dead, is purely coincidental.
******************************************************************
Little known gastromathematical curiosity: let "z" be the
radius and "a" the thickness of a pizza. Then the volume
of that pizza is equal to pi*z*z*a !
******************************************************************
########################################################################
To unsubscribe from the CCP4BB list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
|