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 [CCP4BB@JISCMAIL.AC.UK] de la part de Ethan A Merritt [merr...@u.washington.edu] Envoyé : lundi 23 septembre 2013 23:25 À : CCP4BB@JISCMAIL.AC.UK 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