[phenixbb] Autosol: MIRAS

ash.k at aol.com ash.k at aol.com
Wed Sep 5 19:08:10 PDT 2012


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.



-----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.

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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