Profiling of residue-level photo-oxidative damage in peptides

Abstract

Protein and peptide oxidation is a key feature in the progression of a variety of disease states and in the poor performance of protein-based products. The present work demonstrates a mass spectrometry-based approach to profiling degradation at the amino acid residue level. Synthetic peptides containing the photosensitive residues, tryptophan and tyrosine, were used as models for protein-bound residue photodegradation. Electrospray ionisation tandem mass spectrometry (ESI-MS/MS) was utilised to characterise and provide relative quantitative information on the formation of photoproducts localised to specific residues, including the characterisation of low abundance photomodifications not previously reported, including W + 4O modification, hydroxy-bis-tryptophandione and topaquinone. Other photoproducts observed were consistent with the formation of tyrosine-derived dihydroxyphenylalanine (dopa), trihydroxyphenylalanine, dopa-quinone and nitrotyrosine, and tryptophan-derived hydroxytryptophan, dihydroxytryptophan/N-formylkynurenine, kynurenine, hydroxyformylkynurenine, tryptophandiones, tetrahydro-beta-carboline and nitrotryptophan. This approach combined product identification and abundance tracking to generate a photodegradation profile of the model system. The profile of products formed yields information on formative mechanisms. Profiling of product formation offers new routes to identify damage markers for use in tracking and controlling oxidative damage to polypeptides.

Studies on photoyellowing of silk fibroin and alteration of its tyrosine content

“…In Table 5, it can be concluded that the photodegradation rate of tyrosine was positively correlated with the change rate of the whiteness of silk fibroin, which means that tyrosine content of silk fibroin decreased with the increase in photoyellowing of silk fibroin (Grosvenor, Morton, & Dyer, 2010). Since the change rate of the whiteness of silk fibroin was always higher than the photodegradation rate of tyrosine, it can be deduced that photochemistry reactions of tyrosine were directly related to the photoyellowing of silk fibroin and photochemistry reactions of some other amino acids were also involved in the photoyellowing progress at the same time Xie, Shao, & Zhen, 1993).…”

Upconversion Spectrophotofluorometry

“…Recent investigations on Trp damage via UV irradiation uncovered that a large variety of photoproducts coexist with multiple oxidations taking place at the Trp residue (up to 4), providing a cascade of modifications [57]. Photodamage is an important artifact to carfully monitor in any laser study.…”

Food Proteomics: Mapping Modifications

“…Both redox and Maillard chemistries generate a range of products in susceptible protein regions, and it is the type and abundance profile of these multiple products that results in the overall food properties. Changes in relative abundance in mass spectrometric analysis can be used to track the progressive loss of native peptides and proteins of parent peptides, and the corresponding formation of modification products within those proteins and peptides (Grosvenor et al, 2009). This can be used to evaluate differing protein processing or treatment parameters, as wells as monitor variation under a range of environmental conditions.…”

“…A related approach to evaluating molecular level is the characterisation and tracking of marker peptides. An initial analysis of the protein substrate is performed to identify peptides which fulfil selected criteria, such as reproducible extraction and a unique mass within the MS profile of the sample (Grosvenor et al, 2009). Individual marker peptides are then monitored and tracked.…”