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Re: [ccp4bb]: re Semet from David Borani
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We recently phased a difficult protein with 1 Se per 90 residues using
MAD. Origionally, we were unable to see a signal or find the Se
positions. We subsequently pushed the Se to the oxidative state with
the addition of HOOH. On our second trip to the synchrotron, we got a
great adsorption spectrum and have now found all the seleniums, phased
and are now model building. The oxidation of the selenium appears to be
Two references on oxidation of Se that might prove useful:
1. Shariff, A.J., Koronakis, E., Luisi, B., and Koronakis, V. (2000).
Acta Cryst. D56, 785-788.
2. Smith, J.L. and Thompson, A. (1998). Structure 6, 815-819.
Besides, oxidation should result in the removal of electrons from the Se.
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> I am having trouble posting to the BB;
> Bernard, perhaps you could forward this
> I don't understand the rather cavalier attitude towards Se-Met oxidation.
> one of the proteins I worked on, Apo A-I, oxidation of the (sulfur)
> DRAMATICALLY alters the physicochemical and biological properties of the
> protein. The reason is obvious....Met is a hydrophobic side chain;
> is VERY hydrophilic (it is basically like the universal solvent DMSO) and
> has a
> strong, permanent dipole moment.
> I would imagine that the properties of most proteins would be altered
> if you
> suddenly stuck a (delta+)Se--O(delta-) bond in the middle of the
> core. I think care to prevent Se-Met oxidation is called for.
> David Borhani
> Abbott Bioresearch Center
> Worcester MA 01605
> firstname.lastname@example.org <mailto:email@example.com><mailto:firstname.lastname@example.org>
Stacy D. Benson, Ph.D.
The Wistar Institute Phone: (215) 898-2202
3601 Spruce Street Fax: (215) 898-3868
Philadelphia, PA 19104 E-mail: email@example.com