Oxidative stress occurs in many neurodegenerative diseases including Alzheimer’s disease (AD) and evidence suggests that specific proteins are oxidised in individual diseases. Thus measures of oxidised proteins such as in human biological samples could represent potential disease-specific biomarkers. Protein carbonylation is considered to be an important marker of oxidative stress. In AD in particular, the peptidyl prolyl isomerise Pin1, has been shown to be sensitive to metal-catalysed oxidation with the addition of carbonyl side-chains.