Nature of Fluorescent Compounds Generated by Exposure of Protein to Oxidizing Lipids

Exposure of protein to oxidizing lipid induces fluorescence with excitation wavelengths of 350–360 nm and emission wavelength of 420–430 nm. This fluorescence was studied in freeze-dried emulsions of methyl linoleate with chicken egg lysozyme and other proteins, and in solution with amino acids and several aldehydes. Generation of this fluorescence was found to depend on the reaction of amines with 2, 4-decadienal or one of its breakdown products. Evidence was found suggesting that Schiff base formation of protein lysyl amines with conjugated dicarbonyls other than malonaldehyde is responsible for the fluorescence generated in the lysozymemethyl linoleate system.