Protein carbonyl groups are an important and immediate biomarker of oxidative stress. DNPH tagging of protein carbonyls has been one of the most common measures of oxidative stress. DNP hydrazones formed from the reaction are easily quantifiable at 375 nm. BioVision's Protein Carbonyl Content Assay Kit is designed to provide a simple and accurate method of quantifying carbonyls in protein samples. Using BSA as an example, a 1 mg (~ 15 nmol) sample has a detection limit of about 0.15 nmol carbonyl, where BSA typically contains approximately 1-3 nmol carbonyl/mg.