On the subject of oxidation of methionine, the best resources are Chemical
Modification of Proteins by Means and Feeney (p, 162, 165, 229) and the
book by Roger Lundblad. Probably one would need to add a denaturant to
oxidize all of the methionines.
Chris Halkides
>If you are just doing analytical work and don't need to recover the
>proteins, maybe you could do a mild oxidation of the methionines to the
>sulfoxide. [Perhaps someone out there knows a procedure.] This would
>significantly change the polarity/hydrophibicity of the Met residues, and
>may allow separation of the Nle and Met variants by RPHPLC.
>
>Richard Laursen
>---------------------
>
>>We are working with an E.coli-produced recombinant protein (21,000 MW, 3
>>methionines, no cysteines) that apparently has some methionine-to-norleucine
>>variants. One of these variants chromatographs very closely to the parent
>>protein across a number of purification techniques: cation and anion
>>exchange,
>>HIC, acid rpHPLC. Does anyone have any suggestions about how to specifically
>>enhance resolution between these species, so we can quantitate the variant
>>without doing a peptide map?
>>
>>Vernon
>>
>>Vernon A. Shoup
>>Regeneron Pharmaceuticals, Inc.
>>Rensselaer, NY 12144
>>
>>(518)488-6012
>>vernon.shoup@regpha.com
>
>Richard A. Laursen
>Department of Chemistry
>Boston University
>590 Commonwealth Ave.
>Boston, MA 02215
>Tel (617) 353-2491; FAX (617) 353-6466
>email: <laursen@bu.edu>
Christopher Halkides
Dept. of Chemistry, UNCW
601 S. College Road
Wilmington, NC 28403-3297
(910) 962-7427