LYSOZYME DEGRADATION BY AZO INITIATOR AAPH, FENTON REACTION, AND IONIZING RADIATION

Abstract

Oxidant generators, such as 2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) and the Fenton reaction, have been used to elucidate protein oxidation pathways and subsequently to screen for stabilizers that could prevent potential damage to the protein of interest. The current study evaluated the use of AAPH and the Fenton reaction as forced degradation tools to simulate the effect of terminal sterilization by ionizing radiation using the model protein lysozyme. The results indicate that when the protein is stressed to the same level as the irradiation process, the damage to the protein caused by the stress conditions is different than that caused by the actual irradiation process. In this work, protein aggregation was determined to be the main degradation pathway for the irradiated lysozyme powder. In contrast, oxidation was found to be the main degradation pathway for the lysozyme solution stressed with AAPH and the Fenton reaction. Since the main degradation pathways are different, the use of AAPH or the Fenton reaction as a surrogate for the irradiation process may not be effective for screening protein stabilizers.