Abstract: It is well known that phosphatidylcholine (PC) vesicles are predominant carriers of cholesterol in human bile. Although the interaction of bile salts with PC has been extensively studied, relatively little attention has been given to effects of divalent metal ions on the aggregation properties of PC. We used both light scattering and UV spectroscopies to follow the effects of divalent metal ions on EYPC (egg yellow PC) vesicles. We conclude that when divalent metal ions existed, the mixed vesicles formed by PC and TC (sodium taurocholate) with the ratio of 1:3 were more stable. Free divalent metal ions act to precipitate unilamellar PC vesicles whereas, in combination with sodium taurocholate, these ions act to decrease the size of PC vesicles and induce a phase transition from PC vesicles to mixed micelles. It is a possible reason for gallstones formation when extra free divalent metal ions exist in human bile.

Key words: Phosphatidylcholine, Divalent metal ions, Sodium taurocholate, 　Aggregation properties