采用浊度滴定、 激光光散射谱、 透射电子显微镜和傅里叶变换红外光谱等方法研究了甘氨脱氧胆酸钠(NaGDC)胶束对Ca2+的“缓冲”作用及其机理。 结果表明, NaGDC浓度在CMC以上时, 将延缓甘氨脱氧胆酸钙盐的沉淀, 浓度越高“缓冲”能力越大。 可能的作用机理是当NaGDC浓度小于CMC时, Ca2+直接与GDC－离子作用, 形成甘氨脱氧胆酸钙沉淀； 当NaGDC浓度大于CMC时, 首先, Ca2+与NaGDC胶束亲水面上的羧基作用, 使NaGDC小胶束通过Ca2+桥连接形成纤维状的大胶束。 而后, 随着Ca2+浓度的增加, 纤维状胶束中与Ca2+作用的COO－逐渐增多, 当胶束中Ca2+/Na+比增大到一定值时, 最终形成NanCam(GDC)n＋2m沉淀, 从而延缓了甘氨脱氧胆酸钙盐的生成。 为研究胆汁中表面活性与金属离子的复杂相互作用给出了新思路。Glycodeoxycholate Micelles

In the present article, NaGDC was used to study the Ca2+-bufferingcapability of bile salt micelles. NaGDC is a naturally occurring bile salt whichconstitutes approximately 10 molar percent of bile salt composition ingallbladder. The authors selected glycine conjugated bile salts NaGDC because itprecipitates with Ca2+ ions fast. The Ca2+-buffering property of sodiumglycodeoxycholate (NaGDC) micelles was studied by utilizing turbidity titration,quasi-elastic light scattering (QELS), transmission electron microscopy (TEM) andFourier transform infrared spectroscopy (FTIR). When the concentration of NaGDCwas above the CMC, the precipitation of Ca2+ ions with NaGDC was buffered. TheCa2+-buffering capability was enhanced when the concentration of NaGDC increased.The possible mechanism of Ca2+-buffering by NaGDC micelles was discussed. Whenthe concentration of NaGDC was below the CMC, the Ca2+ ions reacted with GDC-anions to form the Ca(GDC)2 precipitation. However, at the concentration abovethe CMC, NaGDC simple micelles were connected by Ca2+-bridge to form largerfibriform micelles via the interaction of carboxyl groups of NaGDC simplemicelles with Ca2+ ions. When the ratio of Ca2+ to Na+ was enhanced to the fixedvalue, NanCam(GDC)n+2m complexes were precipitated by the further addition ofCa2+ ions.