Mass spectrometric analysis of oxidized tryptophan

✍ Scribed by van de Weert, Marco; Lagerwerf, Fija M.; Haverkamp, Johan; Heerma, Wigger

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 268 KB
• Volume: 33
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199809)33:9<884::aid-jms698>3.0.co;2-s

✦ Synopsis

Oxindolylalanine and oxindolylalanine-containing peptides were prepared by treatment of tryptophan and tryptophan-containing peptides with mixtures of dimethyl sulfoxide and hydrochloric acid in acetic acid (DMSO-HCl-HAc). The reaction between tryptophan and DMSO-HCl-HAc was monitored by fast atom bombardment mass spectrometry (FAB-MS) and the proposed chlorotryptophan intermediate in the reaction was observed. Almost complete conversion of tryptophan to oxindolylalanine was obtained in reaction mixtures containing 3.75 M HCl when the reaction was performed in an open tube. A higher HCl concentration (5.5 M) and a closed reaction tube promoted the formation of by-products, such as dioxindolylalanine and 3-chlorooxindolylalanine. Extensive hydrolysis C-terminal of tryptophan was observed when tryptophan-containing peptides were treated with DMSO-HCl-HAc containing 5.5 M HCl, during which the tryptophan residue was modiÐed to dioxindolylalanine lactone. Hydrolysis was not observed in mixtures containing 3.75 M HCl. The presence of oxindolylalanine in peptides could be demonstrated by characteristic peaks in FAB collision-induced dissociation tandem mass spectra.

1998 John ( Wiley & Sons, Ltd.