Interaction of Pluronic F-68 with monolayers composed of DPPC (1,2-Dipalmytoyl-sn-glycero-3-phosphocholine), POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and their mixture have been studied. A series of isotherms were obtained by compressing mixed PF-68/lipid monolayers over subphase containing varying concentrations of PF-68. Results obtained were analyzed by applying various thermodynamic equations derived from Gibbs adsorption equation. The mole fractions of PF-68 in the monolayer as computed by these equations (except Barnes' equation) agree quantitatively with each other. The computed extent of penetration of PF-68, based on thermodynamic analysis, is also consistent with the following experimental observations: (i) high rate of exclusion of PF-68 from monolayers upon compression of highly expanded monolayers, and (ii) complete expulsion of PF-68 from monolayers at surface pressures well below 30 mN/m. It was concluded from this study that Pluronic F-68 cannot penetrate into the lipid monolayers at surface pressures (∼30 mN/m) believed to correspond to the lateral pressure in plasma membranes. This conclusion is in agreement with the low toxicity of PF-68 towards cells. The present work demonstrates that thermodynamic analysis is a simple, but effective quantitative tool when applied to monolayer penetration experiments.

中文翻译：

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普鲁尼克F-68在脂质单层中的平衡渗透。

Pluronic F-68与由DPPC（1,2-二巴甲酰基-sn-甘油-3-磷酸胆碱），POPC（1-棕榈酰基-2-油酰基-sn-甘油-3-磷酸胆碱）及其混合物组成的单层相互作用研究。通过在包含不同浓度PF-68的亚相上压缩混合的PF-68 /脂质单层膜，获得了一系列等温线。通过应用从吉布斯吸附方程式导出的各种热力学方程式来分析获得的结果。由这些方程式（Barnes方程式除外）计算出的单层中PF-68的摩尔分数在数量上彼此一致。根据热力学分析计算得出的PF-68的渗透程度也与以下实验观察结果一致：（i）在高度膨胀的单分子层压缩后，单分子层中PF-68的排斥率很高，（ii）在远低于30 mN / m的表面压力下从单层完全排出PF-68。从这项研究得出的结论是，Pluronic F-68在认为与质膜侧向压力相对应的表面压力（约30 mN / m）下无法渗透到脂质单层中。该结论与PF-68对细胞的低毒性一致。本工作表明，当应用于单层渗透实验时，热力学分析是一种简单但有效的定量工具。该结论与PF-68对细胞的低毒性一致。本工作表明，当应用于单层渗透实验时，热力学分析是一种简单但有效的定量工具。该结论与PF-68对细胞的低毒性一致。本工作表明，当应用于单层渗透实验时，热力学分析是一种简单但有效的定量工具。