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.