On Thu, 7 Jan 1999, Rod Levine wrote:
> At 10:14 AM 1/7/99 -0800, Suzanne Perry-Riehm wrote:
> >Does anyone have any experience with the retention time of oxidized
> >methionine? I run a PE-ABI 476A and have a client interested in elucidation
> >of MET and it's oxidized form. Thanks in advance.
> >
> Suzanne,
>
> Straight Edman sequencing won't work for locating the sites of methionine
> sulfoxide (which is the form I'm assuming your client is interested in since
> the sulfone rarely occurs). That's because the sulfoxide is reduced back to
> methionine during the Edman reactions. A similar reduction is well known to
> occur during acid hydrolysis for amino acid analysis, which is why you can't
> quantitate methionine sulfoxide in proteins by simple amino acid analysis.
>
> However, if you or your client are willing to add the simple step of cyanogen
> bromide treatment, then you can probably get the information you want. CNBr
> will oxidze methionine to homoserine, with cleavage of the following peptide
> bond. However, methionine sulfoxide is not affected by CNBr. You may have to
> repurify the peptide(s) of interest after the CNBr treatment, and then proceed
> onto the sequencer. The methionine sulfoxide will be reduced back to
> methionine, which will elute at the normal PHT-Met position.
>
> For an alternative approach to locating methionine sulfoxde in proteins with a
> sequencer, consider "simultaneous sequencing" of a peptide mixture. See PNAS
> 93:15036-15040, 1996.
>
> Rod Levine
>
>
>
> NIH
> Bldg 3, Room 106 MSC 0320
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>
> email: rlevine@nih.gov
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> fax: 1 (301) 496-0599
>