Centro de Investigaciones en Química Biológica de Córdoba, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina.
Biophys J. 2010 Sep 8;99(5):1500-9. doi: 10.1016/j.bpj.2010.06.053.
Purified myelin can be spread as monomolecular films at the air/aqueous interface. These films were visualized by fluorescence and Brewster angle microscopy, showing phase coexistence at low and medium surface pressures (<20-30 mN/m). Beyond this threshold, the film becomes homogeneous or not, depending on the aqueous subphase composition. Pure water as well as sucrose, glycerol, dimethylsulfoxide, and dimethylformamide solutions (20% in water) produced monolayers that become homogeneous at high surface pressures; on the other hand, the presence of salts (NaCl, CaCl(2)) in Ringer's and physiological solution leads to phase domain microheterogeneity over the whole compression isotherm. These results show that surface heterogeneity is favored by the ionic milieu. The modulation of the phase-mixing behavior in monolayers is paralleled by the behavior of multilamellar vesicles as determined by small-angle and wide-angle x-ray scattering. The correspondence of the behavior of monolayers and multilayers is achieved only at high surface pressures near the equilibrium adsorption surface pressure; at lower surface pressures, the correspondence breaks down. The equilibrium surface tension on all subphases corresponds to that of the air/alkane interface (27 mN/m), independently on the surface tension of the clean subphase.
纯化的髓磷脂可以在空气/水界面铺展成单分子膜。这些膜通过荧光和布鲁斯特角显微镜进行可视化，显示出在低中和中等表面压力（<20-30 mN/m）下的相共存。超过这个阈值，膜变得均匀或不均匀，取决于水亚相的组成。纯水以及蔗糖、甘油、二甲基亚砜和二甲基甲酰胺溶液（在水中 20%）产生的单层在高表面压力下变得均匀；另一方面，在林格氏液和生理溶液中存在盐（NaCl、CaCl(2)）会导致整个压缩等温线上的相域微不均匀性。这些结果表明，表面异质性受到离子环境的青睐。单层中相混合行为的调制与小角和广角 X 射线散射确定的多层囊泡的行为相平行。仅在接近平衡吸附表面压力的高表面压力下，单层和多层的行为才能达到一致；在较低的表面压力下，这种一致性就会破裂。所有亚相的平衡表面张力都对应于空气/烷烃界面的表面张力（27 mN/m），与清洁亚相的表面张力无关。
