Subcritical Water Hydrolysis of Peptides: Amino Acid Side-Chain Modifications

Previously we have shown that subcritical water may be used as an alternative to enzymatic digestion in the proteolysis of proteins for bottom-up proteomics. Subcritical water hydrolysis of proteins was shown to result in protein sequence coverages greater than or equal to that obtained following di...

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Bibliographic Details
Published in:Journal of the American Society for Mass Spectrometry 2017-09, Vol.28 (9), p.1775-1786
Main Authors: Powell, Thomas, Bowra, Steve, Cooper, Helen J.
Format: Article
Language:English
Subjects:
Amino acids
Analytical Chemistry
Aspartic acid
Bioinformatics
Biotechnology
Chains
Chemistry
Chemistry and Materials Science
Cysteine
Digestion
Electron transfer
Focus: Using Electrons and Radical Chemistry to Characterize Biological Molecules
Focus: Using Electrons and Radical Chemistry to Characterize Biological Molecules: Research Article
Hydrolysis
Liquid chromatography
Mass spectrometry
Methionine
Organic Chemistry
Oxidation
Peptides
Proteins
Proteomics
Scientific imaging
Spectroscopy
Sulfonic acid
Trypsin
Tryptophan
Water loss
Water treatment
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Summary:Previously we have shown that subcritical water may be used as an alternative to enzymatic digestion in the proteolysis of proteins for bottom-up proteomics. Subcritical water hydrolysis of proteins was shown to result in protein sequence coverages greater than or equal to that obtained following digestion with trypsin; however, the percentage of peptide spectral matches for the samples treated with trypsin were consistently greater than for those treated with subcritical water. This observation suggests that in addition to cleavage of the peptide bond, subcritical water treatment results in other hydrolysis products, possibly due to modifications of amino acid side chains. Here, a model peptide comprising all common amino acid residues (VQSIKCADFLHYMENPTWGR) and two further model peptides (VCFQYMDRGDR and VQSIKADFLHYENPTWGR) were treated with subcritical water with the aim of probing any induced amino acid side-chain modifications. The hydrolysis products were analyzed by direct infusion electrospray tandem mass spectrometry, either collision-induced dissociation or electron transfer dissociation, and liquid chromatography collision-induced dissociation tandem mass spectrometry. The results show preferential oxidation of cysteine to sulfinic and sulfonic acid, and oxidation of methionine. In the absence of cysteine and methionine, oxidation of tryptophan was observed. In addition, water loss from aspartic acid and C-terminal amidation were observed in harsher subcritical water conditions. Graphical Abstract ᅟ
ISSN:1044-0305
1879-1123
DOI:10.1007/s13361-017-1676-1