[phenixbb] Geometry Restraints - Anisotropic truncation

Terwilliger, Thomas C terwilliger at lanl.gov
Tue May 1 11:35:00 PDT 2012


Hi Kendall,

A caution on using the free R value to evaluate the utility of applying an anisotropic truncation to the data:  As you remove data with low I/sigma, you will generally improve the free R regardless of whether your model is improved or not.  This is of course true also if you simply remove all the data with I/sigma < 3 or apply any other truncation of that type.

All the best,
Tom T

________________________________________
From: phenixbb-bounces at phenix-online.org [phenixbb-bounces at phenix-online.org] on behalf of Kendall Nettles [knettles at scripps.edu]
Sent: Tuesday, May 01, 2012 11:34 AM
To: PHENIX user mailing list
Subject: Re: [phenixbb] Geometry Restraints - Anisotropic truncation

I have seen dramatic improvements in maps and behavior during refinement following use of the UCLA anisotropy server in two different cases. For one of them the Rfree went from 33% to 28%. I don't think it would have been publishable otherwise.
Kendall

On May 1, 2012, at 11:10 AM, Bryan Lepore wrote:

> On Mon, Apr 30, 2012 at 4:22 AM, Phil Evans <pre at mrc-lmb.cam.ac.uk> wrote:
>> Are anisotropic cutoff desirable?
>
> is there a peer-reviewed publication - perhaps from Acta
> Crystallographica - which describes precisely why scaling or
> refinement programs are inadequate to ameliorate the problem of
> anisotropy, and argues why the method applied in Strong, et. al. 2006
> satisfies this need?
>
> -Bryan
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