Dear Kenneth,
IMO there is no resolution cut-off to decide to go from TLS to individual
anisotropic Bs. I use the number of reflections per atom. You are refining 9
parameters per atom so you need quite a lot. When I have>18 ref/atom I switch
to anisotropic. I try both isotropic and anisotropic Bs with> 13.5 reflections
per atom. You need good evidence that the anisotropic model is better than an
isotropic model, looking at R-free is not good enough. When you add so many
parameters R-free will drop anyway. Ethan Merritt discussed a good test for
this at the CCP4 study weekend. If you use Refmac, I have a tool that uses that
method to compare the logfiles from too models and helps decide which model is
best.
Combining TLS and anisotropic Bs is a bit over the top. You could use
anisotropic Bs and then use TLSMD to extract the bulk movement.
Cheers,
Robbie
> Date: Thu, 7 Apr 2011 19:39:39 -0500
> From: satys...@wisc.edu
> Subject: [ccp4bb] anisotropy vs TLS
> To: CCP4BB@JISCMAIL.AC.UK
>
> peoples:
>
> I know that TLS is a group B factor for regions of proteins that are moving
> the same.
> It is used in low res structures. But at what resolution does one begin
> anisotropic, i.e
> individual aniso for each atom, and leave TLS out. Or can one still use TLS
> to first
> compensate for large motions and then dampen down the individual atoms with
> aniso ADP?
> If both the aniso and TLS are used, how does a person interpret the results?
> What programs
> are there to see just what is large body motions and what is atoms.
> thanks
>
> --
> Kenneth A. Satyshur, M.S.,Ph.D.
> Associate Scientist
> University of Wisconsin
> Madison, Wisconsin 53706
> 608-215-5207
