Winterhalter M, Bürner H, Marzinka S, Benz R, Kasianowicz J J
Lehrstuhl für Biotechnologie, Universität Würzburg, Germany.
Biophys J. 1995 Oct;69(4):1372-81. doi: 10.1016/S0006-3495(95)80006-8.
We have characterized the surface activity of different-sized poly(ethylene-glycols) (PEG; M(r) 200-100,000 Da) in the presence or absence of lipid monolayers and over a wide range of bulk PEG concentrations (10(-8)-10% w/v). Measurements of the surface potential and surface pressure demonstrate that PEGs interact with the air-water and lipid-water interfaces. Without lipid, PEG added either to the subphase or to the air-water interface forms relatively stable monolayers. Except for very low molecular weight polymers (PEGs < 1000 Da), low concentrations of PEG in the subphase (between 10(-5) and 10(-4)% w/v) increase the surface potential from zero (with respect to the potential of a pure air-water interface) to a plateau value of approximately 440 mV. At much higher polymer concentrations, > 10(-1)% (w/v), depending on the molecular weight of the PEG and corresponding to the concentration at which the polymers in solution are likely to overlap, the surface potential decreases. High concentrations of PEG in the subphase cause a similar decrease in the surface potential of densely packed lipid monolayers spread from either diphytanoyl phosphatidylcholine (DPhPC), dipalmitoyl phosphatidylcholine (DPPC), or dioleoyl phosphatidylserine (DOPS). Adding PEG as a monolayer at the air-water interface also affects the surface activity of DPhPC or DPPC monolayers. At low lipid concentration, the surface pressure and potential are determined by the polymer. For intermediate lipid concentrations, the surface pressure-area and surface potential-area isotherms show that the effects due to lipid and PEG are not always additive and that the polymer's effect is distinct for the two lipids. When PEG-lipid-mixed monolayers are compressed to surface pressures greater than the collapse pressure for a PEG monolayer, the surface pressure-area and surface potential-area isotherms approach that of the lipid alone, suggesting that for this experimental condition PEG is expelled from the interface.
我们已经表征了不同尺寸的聚乙二醇（PEG；分子量200 - 100,000 Da）在有无脂质单分子层存在的情况下，以及在广泛的本体PEG浓度范围（10⁻⁸ - 10% w/v）内的表面活性。表面电势和表面压力的测量表明，PEG与空气 - 水界面和脂质 - 水界面相互作用。在没有脂质的情况下，添加到亚相或空气 - 水界面的PEG形成相对稳定的单分子层。除了极低分子量的聚合物（PEG < 1000 Da）外，亚相中低浓度的PEG（10⁻⁵至10⁻⁴% w/v）会使表面电势从零（相对于纯空气 - 水界面的电势）增加到约440 mV的平稳值。在高得多的聚合物浓度下，> 10⁻¹%（w/v），这取决于PEG的分子量且对应于溶液中聚合物可能重叠的浓度，表面电势会降低。亚相中高浓度的PEG会使由二植烷酰磷脂酰胆碱（DPhPC）、二棕榈酰磷脂酰胆碱（DPPC）或二油酰磷脂酰丝氨酸（DOPS）铺展形成的紧密堆积脂质单分子层的表面电势出现类似的降低。在空气 - 水界面添加PEG单分子层也会影响DPhPC或DPPC单分子层的表面活性。在低脂质浓度下，表面压力和电势由聚合物决定。对于中等脂质浓度，表面压力 - 面积和表面电势 - 面积等温线表明，脂质和PEG的影响并非总是相加的，并且聚合物对这两种脂质的影响是不同的。当PEG - 脂质混合单分子层被压缩到表面压力大于PEG单分子层的崩塌压力时，表面压力 - 面积和表面电势 - 面积等温线接近单独脂质的等温线，这表明在这种实验条件下PEG从界面被排出。
