[phenixbb] Anisotropic B-factors with Trucated Data

[Jrh]

Hi
1.7 Angstrom resolution seems to me awfully low for thinking about anisotropic protein model refinement! Ie in terms of number of diffraction data to model parameters. The truncation due to the set up geometry, leading to high <I/sig(I)> at the edge of the data set, IMHO, should not lead to too much oddity (in the atom B factors).
Just my two cents worth,
Best wishes,
John 

Emeritus Prof John R Helliwell DSc


On 31 Jul 2015, at 21:42, "Keller, Jacob" <kellerj at janelia.hhmi.org> wrote:

> Actually, I think I found how to override the iso/aniso decision: under "global parameters," set aniso cutoff to lower resolution. Seems to be working.
> 
> Any thoughts on the more general question about aniso refinement in the case of truncated data, or +/- twinning? Seems twinning changes ML refinement to LSQ, but I am not sure how that changes this.
> 
> Jacob
> 
> -----Original Message-----
> From: phenixbb-bounces at phenix-online.org [mailto:phenixbb-bounces at phenix-online.org] On Behalf Of Keller, Jacob
> Sent: Friday, July 31, 2015 3:53 PM
> To: phenixbb at phenix-online.org
> Subject: [phenixbb] Anisotropic B-factors with Trucated Data
> 
> Dear Crystallographers,
> 
> I have a dataset which was artificially truncated at 1.7 Ang by the limitations of our setup, but the resolution is probably 1.5 Ang or so. I would like to try running anisotropic B refinement in Phenix, but am not sure how to tweak to get this to happen. I know about the parameter:measurement ratio concept, but I think it may still be better than isotropic. NB the dataset is also 42% twinned.
> 
> All the best,
> 
> Jacob Keller
> 
> *******************************************
> Jacob Pearson Keller, PhD
> Looger Lab/HHMI Janelia Research Campus
> 19700 Helix Dr, Ashburn, VA 20147
> email: kellerj at janelia.hhmi.org
> *******************************************
> 
> 
> 
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