Isobaric Labeling Approach to the Tracking and Relative Quantitation of Peptide Damage at the Primary Structural Level

Protein oxidative damage lies behind skin and hair degradation and the deterioration of protein-based products, such as wool and meat, in addition to a range of serious health problems. Effective strategies to ameliorate degenerative processes require detailed fundamental knowledge of the chemistry at the molecular level, including specific residue-level products and their relative abundance. This paper presents a new means of tracking damage-induced side-chain modification in peptides using a novel application for isobaric label quantification. Following exposure to heat and UVA and UVB irradiation, tryptophan and tyrosine damage products in synthetic peptides were characterized and tracked using ESI-MS/MS and iTRAQ labeling-based relative quantification. An in-depth degradation profile of these peptides was generated, enabling the formation of even low-abundance single-residue-level modifications to be sensitively monitored. The development of this novel approach to profiling and tracking residue-level protein damage offers significant potential for application in the development and validation of protein protection treatments.