Effects of Hofmeister anions on DPPC Langmuir monolayers at the air-water interface
Effects of Hofmeister anions on DPPC Langmuir monolayers at the air-water interface
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DOI：
10.1021/jp0481512
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发表时间：
2004-09-30
影响因子：
3.3
通讯作者：
Brezesinski, G
中科院分区：
文献类型：
--
作者：
Aroti, A;Leontidis, E;Brezesinski, G
在这项工作中，我们研究了属于Hofmeister系列的不同单价阴离子的钠盐对DPPC（1，2-二棕榈酰磷脂酰胆碱）的Langmuir单分子膜的影响。所用的盐为NaCl、NaBr、NaNO 3、NaI、NaBF 4、NaClO 4和NaSCN。通过表面压-面积等温线、布鲁斯特角显微镜（BAM）、掠入射X射线衍射（GIXD）和红外反射吸收光谱（IRRAS）研究了脂相的单层相行为和形态结构。在亚相中的电解质的存在下，被发现增加在一个固定的面积每分子的表面压力，表明稳定的单层的液体膨胀相。这种增加对于不同的阴离子和不同的电解质浓度是不同的。X射线衍射和红外光谱实验表明，中等浓度的离液阴离子，如I-，不显着改变的构象和包装的烃链的性质。即使在相当高的电解质浓度下，液体凝聚相中的脂质分子的晶格参数和排序基本上不受影响。这一发现表明，阴离子分区或绑定到松散的液体膨胀相，从而提供该相的熵稳定，但不渗透到或绑定到域的液体凝聚相。这一有趣的结果进行了讨论的阴离子与脂质界面的相互作用的可能模式。
In this work we investigated the effect of sodium salts of different monovalent anions belonging to the Hofmeister series on Langmuir monolayers of DPPC (1,2-dipalmitoyl phosphatidylcholine). The salts used were NaCl, NaBr, NaNO3, NaI, NaBF4, NaClO4, and NaSCN. The monolayer phase behavior and the morphology and structure of the lipid phases were studied by surface pressure-area isotherms, Brewster Angle Microscopy (BAM), Grazing Incidence X-ray Diffraction (GIXD), and Infrared Reflection-Absorption Spectroscopy (IRRAS). The presence of electrolytes in the subphase was found to increase the surface pressure at a fixed area per molecule, indicating a stabilization of the liquid-expanded phase of the monolayer. This increase is different for different anions and different electrolyte concentrations. X-ray diffraction and infrared spectroscopy experiments show that moderate concentrations of chaotropic anions, such as I-, do not significantly change the conformation and packing properties of the hydrocarbon chains. The lattice parameters and the ordering of the lipid molecules in the liquid-condensed phase remain essentially unaffected, even at quite high electrolyte concentrations. This finding suggests that anions partition into or bind to the looser liquid-expanded phase, thus providing entropic stabilization of that phase, but do not penetrate into or bind to the domains of the liquid-condensed phase. This intriguing result is discussed in terms of the possible modes of interaction of anions with lipid interfaces.