[Study on the mechanism of Ca2+-buffering by sodium glycodeoxycholate micelles].

In the present article,NaGDC was used to study the Ca2+-buffering capability of bile salt micelles.NaGDC is a naturally occurring bile salt which constitutes approximately 10 molar percent of bile salt composition in gallbladder.The authors selected glycine conjugated bile salts NaGDC because it precipitates with Ca2+ ions fast.The Ca2+-buffering property of sodium glycodeoxycholate(NaGDC) micelles was studied by utilizing turbidity titration,quasi-elastic light scattering(QELS),transmission electron microscopy(TEM) and Fourier transform infrared spectroscopy(FTIR).When the concentration of NaGDC was above the CMC,the precipitation of Ca2+ ions with NaGDC was buffered.The Ca2+-buffering capability was enhanced when the concentration of NaGDC increased.The possible mechanism of Ca2+-buffering by NaGDC micelles was discussed.When the 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 above the CMC,NaGDC simple micelles were connected by Ca2+-bridge to form larger fibriform micelles via the interaction of carboxyl groups of NaGDC simple micelles with Ca2+ ions.When the ratio of Ca2+ to Na+ was enhanced to the fixed value,NanCam(GDC)n+2m complexes were precipitated by the further addition of Ca2+ ions.