QUASI-ELASTIC LIGHT-SCATTERING STUDIES OF AQUEOUS BILIARY LIPID SYSTEMS - SIZE, SHAPE, AND THERMODYNAMICS OF BILE-SALT MICELLES
QUASI-ELASTIC LIGHT-SCATTERING STUDIES OF AQUEOUS BILIARY LIPID SYSTEMS - SIZE, SHAPE, AND THERMODYNAMICS OF BILE-SALT MICELLES
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DOI：
10.1021/bi00581a024
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发表时间：
1979-01-01
期刊：
影响因子：
2.9
通讯作者：
BENEDEK, GB
中科院分区：
文献类型：
--
作者：
MAZER, NA;CAREY, MC;BENEDEK, GB
通过测量自相关函数和从胆盐水溶液散射的光的时间平均强度，确定了胆汁盐胶束的平均流体动力学半径 (.hivin.Rh)、形状、聚集数 (.hivin.n) 和多分散性，作为胆汁销售种类、浓度、温度以及 NaCl 和尿素浓度的函数。三羟基胆盐牛磺胆酸盐 (TC) 形成的胶束比二羟基胆盐牛磺脱氧胆酸盐 (TDC)、牛磺熊去氧胆酸盐 (TUDC) 和牛磺鹅脱氧胆酸盐 (TCDC) 更小，后者的大小按以下顺序变化：TDC > TCDC > TUDC。在 0.15 M NaCl 中，.hivin.Rh 和 .hivin.n 值对胆汁盐浓度的依赖性较弱，而在 0.6 M NaCl 中，胶束随着浓度的增加而明显生长。随着温度从 60 降低到 20°C，胶束生长的程度增加。 C 但会因添加尿素 (0-6 M) 而降低。大胶束呈棒状且相当多分散。这些数据在定量上与胆汁盐聚集的两阶段模型一致，其中胆汁盐单体首先在临界胶束浓度下疏水性缔合，形成小球状初级胶束。在较高的胆汁盐浓度下，初级胶束然后聚合成棒状次级胶束。确定了该过程的聚合常数（K）作为每个物理化学变量的函数。从K值的热力学分析可以得出结论，次级胶束形成的驱动力也是初级胶束表面与水性溶剂之间不利的疏水相互作用，水性溶剂主要是由焓引起的。 K 的 NaCl 依赖性可以从 Verwey-Overbeek 双层排斥理论预测，尿素对次级胶束形成的影响与非极性氨基酸侧基从水转移到尿素溶液的自由能的实验数据一致。
From measurements of the autocorrelation function and the time-averaged intensity of light scattered from aqueous bile salt solutions, the mean hydrodynamic radius (.hivin.Rh), shape, aggregation number (.hivin.n), and polydispersity of bile salt micelles as a function of bile sale species, concentration, temperature, and NaCl and urea concentrations were determined. The trihydroxy bile salt taurocholate (TC) forms smaller micelles than the dihydroxy bile salts taurodeoxycholate (TDC), tauroursodeoxycholate (TUDC), and taurochenodeoxycholate (TCDC), the latter species vary in size in the following order: TDC > TCDC > TUDC. In 0.15 M NaCl the .hivin.Rh and .hivin.n values are weakly dependent on bile salt concentration, whereas in 0.6 M NaCl the micelles grow appreciably with increasing concentration. The extent of micellar growth increases as the temperature is lowered from 60 to 20.degree. C but is diminished by the addition of urea (0-6 M). The large micelles are rod-like and quite polydisperse. These data are quantitatively consistent with a 2-stage model of bile salt aggregation in which bile salt monomers first associate hydrophobically at the critical micellar concentration to form small globular primary micelles. At higher bile salt concentrations the primary micelles then polymerize into rod-like secondary micelles. The polymerization constant (K) for this process as a function of each physical-chemical variable was determined. From a thermodynamic analysis of the K values, it is concluded that the driving force for secondary micelle formation is also an unfavorable hydrophobic interaction between the surface of the primary micelle and the aqueous solvent which is largely enthalpic in origin. The NaCl dependence of K can be predicted from the Verwey-Overbeek theory of double layer repulsion and the influence of urea on secondary micelle formation is consistent with experimental data for the free energy of transferring nonpolar amino acid side groups from water to urea solutions.