We often use a "S-SAD" type data collection (there would be no need for
enormous redundancy) which, if your model is correct, should show up the S
positions in the same way as a Se-met would show up the Se positions. Good way
of "validating" your model and a help to tracing.
Cheers
Andy
________________________________________
De : CCP4 bulletin board [[email protected]] de la part de Ethan A Merritt
[[email protected]]
Envoyé : lundi 23 septembre 2013 23:25
À : [email protected]
Objet : Re: [ccp4bb] tricky mr problem
On Monday, 23 September, 2013 22:01:32 RHYS GRINTER wrote:
> Hi all,
>
> I have been attempting to find a MR solution for a low resolution data set
> (3.9A), with pretty poor merging stats of a 22 strand membrane beta barrel
> I'm working on.
>
> I've created a trimmed poly-alanine from a structure of 17% identity, that
> gives a solution with a Tfz of 14.3 with two molecules per asu (llg is around
> 900). I'm guessing this in a genuine solution, but the map is too poor to
> build into.
>
> Does anyone have any advice as to proceed from here? It may be just a case of
> needing better resolution data to work with, but would this indicate that
> Selenomet derivative crystals won't be needed for this structure?
Apart from whether you "need" SeMet for phasing, when you are having trouble
fitting into
poor maps it can help a lot to have the location of methionines pinned down by
peaks
in an anomalous difference Fourier map.
Ethan
