OXIPEP: mass spectrometry strategy to characterize protein carbonylation.

Here we describe a peptide-centric approach (OXIPEP), where carbonylated residues within proteins are derivatized with biotin-hydrazide, enriched and identified by mass spectrometry. The strength of the method lies in an improved protocol for elution of biotinylated peptides from monomeric avidin resin using hot water (95C) and increased sensitivity achieved by reduction of sample losses during sample preparation and chromatographic steps. For the first time advanced bioinformatics analysis utilising diagnostic biotin fragment ions is used to facilitate semi-automatic in silico evaluation of biotin labelling and to increase the reliability of carbonyl peptide identification.