Mass spectrometric analysis of oxidized tryptophan
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 modified 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.
Van de Weert, Marco,Lagerwerf, Fija M.,Haverkamp, Johan,Heerma, Wigger
p. 884 - 891
(2007/10/03)
Preparative Separation of the Diastereomers of Dioxindolyl-L-alanine and Assignment of Stereochemistry at C-3
The diastereomers of dioxindolyl-L-alanine are obtained in a 1:1 ratio by air oxidation of oxindolyl-L-alanine.Preparative separation of the diastereomers is achieved by reverse-phase HPLC.Stereochemistry of the hydroxyl group at C-3 is assigned by transformation to a related pair of diastereomers of known stereochemistry.
Labroo, Rita B.,Cohen, Louis A.
p. 4901 - 4904
(2007/10/02)
Oxidative transformation of tryptophan to 3-(2-aminophenyl)-2-pyrrolidone and kynurenine
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Nakagawa,Kato,Fukazawa,et al.
p. 5871 - 5874
(2007/10/02)
The decomposition of tryptophan in acid solutions: specific effect on hydrochloric acid
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Ohta,Suzuki,Todo,Kurechi
p. 1767 - 1771
(2007/10/02)
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