[Study on the mechanism of Ca2+-buffering by sodium glycodeoxycholate micelles].
In the present article, NaGDC was used to study the Ca(2+)-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 Ca(2+)-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 Ca(2+)-buffering capability was enhanced when the concentration of NaGDC increased. The possible mechanism of Ca(2+)-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 Ca(2+)-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, Na(n)Ca(m) (GDC)(n+2m) complexes were precipitated by the further addition of Ca2+ ions.
Chen
Hu-He
HH
College of Chemistry and Molecular Engineering, State Key Laboratory of Rare Earth Material Chemistry and Application, Peking University, Beijing 100871, China.
Yu
Fang-Ting
FT
Yang
Zhan-Lan
ZL
Xu
Yi-Zhuang
YZ
Weng
Shi-Fu
SF
Wu
Jin-Guang
JG