Effects of Calcium Ions on Thermodynamic Properties of Mixed Bilirubin/Cholesterol Monolayers

bilirubin/cholesterol 的混合单层行为通过表面压力区域被学习(包含钙离子的各种各样的集中的水的溶液上的 -A) 等温线。把等温线基于 A 的数据，吝啬的区域每分子，倒塌压力，表面压缩的可能性模量，分子的区域，混合的免费精力，和过量释放的过量在不同 subphases 上单层混合的精力被计算。结果证明在有在 subphase 的 Ca2+ 的混合单层的结构的扩大，并且在空气 / 水接口的部件的非理想的混合在过量从添加规则与积极偏差被观察分子的区域。在部件之间的可混和性随 subphase 的 Ca2+ 的集中的增加被削弱。事实显示在 Ca2+ 和二个部件之间的协作的存在。混合单层，到胆固醇的 bilirubin 的臼齿的比率在是 3:2，从纯水上的一个热力学的观点是更稳定的。但是稳定的 3:2 stoichiometry 建筑群随 subphase 的 Ca2+ 的集中的增加被破坏。否则，混合单层在 Ca2+ subphase 上在更低的表面压力有更多的热力学的稳定性。

The mixed monolayer behavior of bilirubin/cholesterol was studied through surface pressure-area （π-A） isotherms on aqueous solutions containing various concentrations of calcium ions. Based on the data of π-A isotherms, the mean area per molecule, collapse pressure, surface compressibility modulus, excess molecular areas, free energy of mixing, and excess free energy of mixing of the monolayers on different subphases were calculated. The results show an expansion in the structure of the mixed monolayer with Ca^2＋ in subphase, and non-ideal mixing of the components at the air/water interface is observed with positive deviation from the additivity rule in the excess molecular areas. The miscibility between the components is weakened with the increase of concentration of Ca^2＋ in subphase. The facts indicate the presence of coordination between Ca^2＋ and the two components. The mixed monolayer, in which the molar ratio of bilirubin to cholesterol is 3：2, is more stable from a thermodynamic point of view on pure water. But the stable 3：2 stoichiometry complex is destroyed with the increase of the concentration of Ca^2＋ in subphase. Otherwise, the mixed monolayers have more thermodynamic stability at lower surface pressure on Ca^2＋ subphase.