CARBONYL groups, such as ketones and aldehydes, are a commonindicator of protein oxidation. Protein oxidation is caused as a result of exposure to reactive oxygen species (ROS) and is a common marker in various diseases as well as aging. BioAssay Systems' Carbonyl Assay Kit is based on an improved method, where 2,4-dinitrophenylhydrazine (DNPH) reacts with carbonyl groups to produce a colored compound at 375 nm. The intensity of this colored compound is directly proportional to the carbonyl groups in the sample.