Introduction of carbonyl groups into proteins by the lipid peroxidation product, malondialdehyde.

Incubation of model proteins with the toxic lipid peroxidation product malondialdehyde resulted in a time- and concentration-dependent increase in carbonyl contents. Carbonyl groups were detected either spectrophotometrically or immunochemically after derivatization with 2,4-dinitrophenylhydrazine. Although significant adduction occurred when modifications were performed at pH 7.0, carbonyl formation was most extensive when modifications were carried out at pH 4.0 or pH 5.0. Similarly, formation of intermolecular crosslinks was most extensive when reactions were carried out under mildly acidic conditions. Our results raise the possibility that malondialdehyde adducts contribute to the carbonyl content of proteins recovered from mammalian tissues.