We have successfully used microPIXE (see the link for an excellent review of the method) in collaboration with Univ. of Surrey, and this proved to be the most precise way of determining Se levels in our case - we are dealing with a glycosylated protein. We tried mass spec, but this didn't allow us to quantify incorporation well because of the broad peaks obtained for the sample due to glycosylation.

On Sep 28, 2009, at 4:50 PM, Elspeth Garman wrote:

Dear Marija
This can be done by Proton Induced X-ray Emission on a tiny sample (0.2microl) of liquid protein to get the sulphur to selenium ratio and thus work out the substitution of Selenium.
See:
http://www.ionbeamcentre.co.uk/index.php?target=3:68
and contact
Dr. Chris Jeynes for this service:
[log in to unmask]
Best wishes
Elspeth

Marija Backovic wrote:
Dear all -

Does anyone know of a facility that provides amino acid analysis for determination of SeMet incorporation in a recombinant protein?

I contacted centers at Grenoble and Uppsala, but SeMet determination is not something they routinely do.

Any suggestions would be highly appreciated!

Best,

Marija

Marija Backovic, Ph.D.

Pasteur Institute
Department of Virology
25 rue du Dr Roux
75015 Paris
France

+33 (0)1 45 68 82 87

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Elspeth F. Garman,
President, British Crystallographic Association
Professor of Molecular Biophysics, University of Oxford
Visiting Professor in Chemistry, University of Durham
Postal address:
Laboratory of Molecular Biophysics,
Department of Biochemistry,
University of Oxford,              Tel: (44)-1865-613297
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       http://www.biop.ox.ac.uk/www/garman/gindex.html -----------------------------------------------------

Marija Backovic, Ph.D.

Pasteur Institute

Department of Virology

25 rue du Dr Roux

75015 Paris

France

+33 (0)1 45 68 82 87