[phenixbb] question on the missing fobs filled maps

Frank von Delft frank.vondelft at sgc.ox.ac.uk
Tue Nov 9 13:29:35 PST 2010


Hi Sasha

That's a great idea! -- I'd be interested.  Actually, what I'm most 
interested about is how you walk through reciprocal space.  Any special 
algorithm, or is it simple clustering by neighbours?

Cheers!
Frank




On 09/11/2010 08:11, Alexandre OURJOUMTSEV wrote:
>
> Hello,
>
> Continuing and confirmating Pavel's last comments:
>
> yes, we saw a number of practical cases when non-uniformly distributed 
> missed data, even a small percent, caused great map distortions (some 
> example are listed in our manuscript recently submitted to 
> J.Appl.Cryst). To track this situation, recently we have developed a 
> small python-based program that starting from your MTZ file searches 
> for connected regions of such unmeasured reflections, gives their 
> characteristics and visualizes the regions on the user's request. 
> Presence of such regions may make your maps ugly even when the phases 
> are perfect.
>
>       For an official release when ready the program will be available 
> at the Web site of the institute; for a time being if you want to test 
> the current version please send me a mail to
>
> sacha at igbmc.fr
>
>
> With best regards,
>
> Sacha Urzhumtsev
>
> /-----Message d'origine-----
> De : phenixbb-bounces at phenix-online.org 
> [mailto:phenixbb-bounces at phenix-onl//ine.org] De la part de Pavel Afonine
>
> ///
>
> / Hi Fengyun,/
>
> //
>
> /> I am interesting in that at what completeness of the dataset, will one/
>
> /> use the missing fobs filled map for model building confidently without/
>
> /> too much bias included?/
>
> //
>
> /I'm not aware of any systematic study on this matter, although at some/
>
> /point I reviewed the available literature./
>
> //
>
> /There are numerous examples of how the data incompleteness distorts the/
>
> /map, and literature that discusses this. Interestingly, sometimes much/
>
> /smaller amount of systematically missing reflections, such as plane or/
>
> /cone in reciprocal space, may have much drastic effect than a larger/
>
> /amount of randomly missing data (if you are "lucky" enough it can 
> mask entire structural domain)./
>
>
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