Egg yolk lipoproteins, low density lipoprotein fraction and high density lipoprotein fraction, were incubated with metallic salts for the periods of ten days. Fluorescence intensity at Em 430455nm, Ex 355390nm in the incubated solution increased by oxidation of the lipid moiety of lipoproteins catalyzed by metalic ions. Changes of lipoproteins were prevented by addition of ethylenediaminetetraacetic acid (EDTA).
On the other hand, the ultrasonic irradiation on egg yolk lipoproteins provokes oxidation of the lipid moiety of lipoproteins, but no development of fluorescence spectrum was observed in the course of oxidation by the ultrasonic irradiation. These results suggest that oxidation occurs in the lipid moiety of lipoproteins during the ultrasonic irradiation similar to the case of the lipoprotein oxidized by metalic ion catalysis, but the increase of fluorescence intensity is not accelerated by the ultrasonic irradiation.