Gonçalves da Silva Amélia M, Romão Rute I S
Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, 1049-001 Lisboa, Portugal.
Chem Phys Lipids. 2005 Oct;137(1-2):62-76. doi: 10.1016/j.chemphyslip.2005.06.004.
The behaviour of binary mixtures involving dipalmitoylphosphatidylcholine (DPPC), dioctadecyldimethylammonium bromide (DODAB) and oleic acid (OA) was investigated at the air-water interface by surface pressure-area (pi-A) measurements and by Brewster angle microscopy (BAM). Thermodynamic analysis indicates for the system DPPC/DODAB miscibility with strong negative deviations from the ideal behaviour, from low to high surface pressures over all the composition range. For systems DODAB/OA and DPPC/OA, thermodynamic analysis and BAM observation indicate miscibility from low to intermediate surface pressures, and phase separation in a limited range of composition at high surface pressures. The interaction of nicotinic acid (NA) with pure lipids and with selected compositions of mixed systems was investigated. Significant positive deviations of pi-A isotherms in the presence of NA indicate attractive interactions between NA and the polar groups of DPPC and DODAB. NA easily penetrates in expanded regimes while it tends to be segregated from condensed regimes in mixed monolayers.
通过表面压力-面积（π-A）测量和布鲁斯特角显微镜（BAM）研究了涉及二棕榈酰磷脂酰胆碱（DPPC）、二辛基二甲基溴化铵（DODAB）和油酸（OA）的二元混合物在空气-水界面的行为。热力学分析表明，对于DPPC/DODAB体系，在整个组成范围内，从低表面压力到高表面压力，其混溶性与理想行为存在强烈的负偏差。对于DODAB/OA和DPPC/OA体系，热力学分析和BAM观察表明，在低到中等表面压力下混溶，在高表面压力下在有限的组成范围内发生相分离。研究了烟酸（NA）与纯脂质以及混合体系选定组成之间的相互作用。在存在NA的情况下，π-A等温线的显著正偏差表明NA与DPPC和DODAB的极性基团之间存在吸引相互作用。NA在膨胀状态下容易渗透，而在混合单分子层中，它倾向于从凝聚状态中分离出来。
