[phenixbb] Autosol: MIRAS

[Francis E Reyes]

This one is solvable, but with extreme difficulty. I recently  completed a structure solution with experimental phases starting at 5.0 A using phase information from multiple derivatives. 

How would you describe a somewhat satisfactory map?

F

On Sep 5, 2012, at 7:08 PM, ash.k at aol.com wrote:
> 
> 
> Hi Shya,
> 
>  I did wavelength scan, got a good signal for Se and used appropriate wavelengths for data collection and also used experimental f' and f'' values for phasing. I think the reasons SAD or MAD for SeMet data is not working are (i) low resolution: 3.7 for SeMet (Anomalous data is up to 4.8A) (ii) I should have mentioned this earlier: 3 out of 6 Se are very close to N-terminus, possible they are disordered. Unit cell is also some what big..100, 120 and 320A; F222 space group.
> 
> AK  
> 
> -----Original Message-----
> From: Shya Biswas <shyabiswas at gmail.com>
> To: PHENIX user mailing list <phenixbb at phenix-online.org>
> Sent: Thu, Sep 6, 2012 7:29 am
> Subject: Re: [phenixbb] Autosol: MIRAS
> 
> Hi AK,
> Did you do a wavelength scan when you collected the SE dataset you
> need to put the values of f' and f'' from your wavelength scan in
> order to locate the heavy atom sites, 6 methionine should be enough to
> phase your molecule.
> Shya
> 
> On Wed, Sep 5, 2012 at 9:25 PM,  <ash.k at aol.com> wrote:
> > Hi all,
> >
> > I am trying to solve a structure through experimental phasing using AUTOSOL.
> > I have a couple of heavy atom derivative datasets (Hg, La, Eu, Cd) and also
> > a SeMet data. Unfortunately all the datasets are of low resolution
> > (3.7-4.2A) and there are possibly 4-8 molecules in the asu. MIR, SAD and MAD
> > alone did not give any convincing solution.
> >
> > However, MIRAS, with a combination of few heavy atom datasets and the
> > anomalous data from SeMet crystals, gave a somewhat satisfactory map. But
> > the heavy atom site picked by AUTOSOL list only one of the heavy atoms i.e.
> > Lanthanum. In another set of run, the solution of which was not convincing,
> > the heavy atom substructure had only Hg. There are 6 Met out of 200 residues
> > in one molecule and mass spec results show that Se incorporation is 100%.
> >
> > Now, my doubt is that why does the heavy atom substructure contain only La
> > and how can I get the substructure involving Se from this solution (or the
> > datasets used)?  Se location is going to help me a lot for finding a
> > starting point to assign side chains.
> >
> > Any suggestion would be greatly appreciated.
> >
> > Thanks
> > AK
> >
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