# Fragmentation of Peptide Disulfides under Conditions of Negative Ion Mass Spectrometry: Studies of Oxidized Glutathione and Contryphan

Thakur, Suman S and Balaram, Padmanabhan (2008) Fragmentation of Peptide Disulfides under Conditions of Negative Ion Mass Spectrometry: Studies of Oxidized Glutathione and Contryphan. In: Journal of the American Society for Mass Spectrometry, 19 (3). pp. 358-366.

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## Abstract

The fragmentation of positive and negative ions of peptide disulfides under mass spectrometric conditions yields distinctly different product ion distributions. A negative ion upon collision induced dissociation yields intense product ions, which correspond to cleavage at the disulfide linkage. The complete assignment of the product ions obtained upon fragmentation of oxidized glutathione in an ion trap is presented. The cleavage at the disulfide site is mediated by abstraction of C(\alpha)H and C(\beta)H protons resulting in product ions derived by neutral loss of $H_2S_2$ and \$H_2S. The formation of peptide thioaldehydes and persulfides at the cysteine sites is established. Dehydroalanine formation at the Cys residue is predominant. The case of a contryphan, a cyclic peptide disulfide derived from Conus snail venom, illustrates the utility of negative ion mass spectrometry in disulfide identification. Complementary information is derived by combining the fragmentation patterns obtained from positive and negative ions of disulfide containing peptides.

Item Type: Journal Article Copyright of this article belongs to American Society for Mass Spectrometry. Division of Biological Sciences > Molecular Biophysics Unit 09 Apr 2008 19 Sep 2010 04:44 http://eprints.iisc.ernet.in/id/eprint/13711