Immunological Detection and Quantification of Oxidized Proteins by Labelling with Digoxigenin

Abstract

An immunological assay, based on the digoxigenin/anti-digoxigenin system, was developed to detect and quantify carbonyl moieties that result from oxidative damage to proteins. Bovine serum albumin (BSA) was oxidized by a hydroxyl radical-generating system consisting of ascorbate/Fe(III)/O₂. The resulting albumin-derived carbonyls were labelled with digoxigenin-hydrazide and detected by dot blotting with an anti-digoxigenin antibody conjugated to alkaline phosphatase. Quantification was carried out by a densitometric analysi. This system allows the detection of a pmole-amount of carbonyl groups on blots. The assay covers a range of sensitivity from 1.26 to 126 pmoles. Another feature of this method is its application to a complex protein mixture (homogenate) to analyze the oxidative status of individual proteins, as are shown for intestinal brush border membrane homogenate of a rat.

• oxidative modification
• protein oxidation
• immunological detection
• digoxigenin
• aging