Cysteic Acid is the Chemical Mediator of Automotive Clearcoat Damage Promoted by Dragonfly Eggs

摘要

The damage caused by dragonfly eggs on automotive clearcoats exposed to sunlight occurs by a chemical mechanism similar to that caused by acid rain. Cysteine and cystine residues present in rtragonfly eggs are oxidized during the egg hardening process, which releases hydrogen peroxide, to a cysteic acid derivative, a strong acid capable to catalyze the hydrolysis of acrylo/melamine clearcoat polymer. Cysteic acid was indeed identified and quantified by ion-exchange HPLC in dragonfly egg extracts submitted to oxidation by H_2O_2 follbwed by acid digestion. Moreover, H_2O_2 concentra- tion, temperature, and exposure time profiles of cysteic acid formation as well as an apparent activation energy for cysteine (in dragonfly eggs) oXidation to cysteic acid by H_2O_2 (32 +- 2 kJ/mol) were determined.