Oxidation of methionine to methionine sulfoxide as a side reaction of cyanogen bromide cleavage

✍ Scribed by Regula Joppich-Kuhn; Jeffrey A. Corkill; Roger W. Giese

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 378 KB
• Volume: 119
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(82)90666-2

✦ Synopsis

In addition to cleaving the peptide bond in N-pentafluorobenzoyl-methionyl-glycine, cyanogen bromide can also oxidize this peptide to the corresponding sulfoxide, particularly at a higher pH. The yields of this sulfoxide are 1, 8, 64, and 97% when the reaction conditions are 70% formic acid, 0.1 M hydrochloric acid, pH 3.5 citrate buffer, and pH 6.5 phosphate buffer, respectively. Thus, it is no longer acceptable to assume that any methionine sulfoxide arising at the conclusion of a cleavage reaction by cyanogen bromide is necessarily due to partial oxidation of the methionine in the starting peptide or protein.