Abstract
Treatment of lecithin liposomes with 100 μM ascorbic acid and 10 μM ferrous ion resulted in the formation of fluorescent products exhibiting an emission maximum at 430 nm and a decrease in the fluorescence intensity of 8-anilino-1-naphthalenesulfonate (ANS) bound to the liposomes without change in the emission maximum. The degree of ascorbic acid/Fe2+-induced decrease in the ANS fluorescence was dependent on the extent of fluorescent product formation. The results of kinetic studies on ANS-binding to the liposomes showed that treatment of the liposomes with ascorbic acid/Fe2+ causes an increases of the apparent dissociation constant (Kd) of ANS-liposome complex. This indicates that lipid peroxidation of the liposomes by treatment with ascorbinc acid/Fe2+ decreases the binding affinity of ANS to the liposomes. In addition, it was also found that there is a good correlation between degrees of the Kd value and the formation of fluorescent products. The fluorescence properties, i.e. emission maximum and response of the fluorescence intensity for borohydride reduction, of the products formed by lipid peroxidation of the liposomes were simillar to those derived from modification of the liposomes wiht monofunctional aldehydes such as acetaldehyde and heptaldehyde. From these results, it is suggersted that the decrease of ANS-binding affinity to the liposomes by treatment with ascorbic acid/Fe2+ may be due to changes in teh surface charge density of the liposomes relating to the formation of fluorescent products.
