Romão Rute I S, Gonçalves da Silva Amélia M
Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, 1049-001 Lisboa, Portugal.
Chem Phys Lipids. 2004 Aug;131(1):27-39. doi: 10.1016/j.chemphyslip.2004.03.009.
The behaviour of dipalmitoylphosphatidylcholine (DPPC), mixed with stearonitrile (SN), was investigated at the air-water interface by surface pressure-area (pi-A) measurements and by direct visualisation of monolayers by Brewster angle microscopy (BAM). The pi-A-X diagram of system DPPC/SN was compared with the corresponding diagrams of systems DPPC/stearic acid (SA) and DPPC/octadecanol (OD) at 20 degrees C. Monolayers of the three systems reach the closest packing of alkyl chains in the 0.4-0.6 range of XDPPC. Thermodynamic analysis indicates miscibility in the three binary systems with negative deviations from the ideal behaviour. Morphological features of system DPPC/SN change significantly with XDPPC and temperature in the range 10-30 degrees C. At 10 and 20 degrees C mixed monolayers form condensed states from low pi all over the composition range. At 30 degrees C, the liquid-expanded (LE)--liquid-condensed (LC) phase transition occurs at increasing pi with XDPPC. The shape and size of condensed domains change with XDPPC and pi. Contrarily to the behaviour of pure components, mixed monolayers of DPPC/SN exhibit orientational order in the 0.2-0.6 mol fraction range of DPPC. BAM observation confirmed the partial miscibility indicated by GE data in a limited range of compositions at 30 degrees C.
通过表面压力-面积（π-A）测量以及用布鲁斯特角显微镜（BAM）直接观察单分子层，研究了在空气-水界面处二棕榈酰磷脂酰胆碱（DPPC）与硬脂腈（SN）混合后的行为。将DPPC/SN体系的π-A-X图与20℃下DPPC/硬脂酸（SA）和DPPC/十八烷醇（OD）体系的相应图进行了比较。这三个体系的单分子层在XDPPC为0.4 - 0.6范围内达到烷基链的最紧密堆积。热力学分析表明这三个二元体系是可混溶的，但与理想行为存在负偏差。DPPC/SN体系的形态特征随XDPPC和10 - 30℃范围内的温度显著变化。在10℃和20℃时，混合单分子层在整个组成范围内从低π值形成凝聚态。在30℃时，随着XDPPC增加，液体扩张（LE）-液体凝聚（LC）相变在π值增加时发生。凝聚域的形状和大小随XDPPC和π值变化。与纯组分的行为相反，DPPC/SN的混合单分子层在DPPC的0.2 - 0.6摩尔分数范围内表现出取向有序。BAM观察证实了在30℃有限组成范围内GE数据所表明的部分混溶性。
