Immunochemical detection of oxidized proteins.

An immunochemical assay was developed to detect carbonyl moieties that result from oxidative damage to proteins. Bovine serum albumin was reacted with hydroxyl radicals generated via a Fenton-like mechanism or by a radiolysis mechanism. The resulting albumin-derived carbonyls were reacted with 2,4-dinitrophenylhydrazine, giving the corresponding hydrazones, which were detected by Western blot using anti-dinitrophenyl antisera. The immunoblot demonstrated a concentration-dependent increase in carbonyl formation, as well as fragmentation of the albumin into two distinct bands with molecular masses of 51 and 45 kDa when oxidized with the Fenton-like mechanism, and 62 and 46 kDa when oxidized by radiolysis. Analysis of the immunoblot using laser densitometry indicated a linear relationship between carbonyl groups and increasing treatment from radiolysis. This immunochemical assay was approximately 3 orders of magnitude more sensitive than the spectrophotometric method and was able to determine the molecular mass of carbonyl-modified polypeptides in the detection of oxidative damage.