Sobolewski Tess N, Walker Robert A
Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
Montana Materials Science and Engineering, Montana State University, Bozeman, Montana 59717, United States.
J Phys Chem B. 2025 Jul 24;129(29):7528-7538. doi: 10.1021/acs.jpcb.5c02410. Epub 2025 Jul 11.
Vibrational sum frequency generation (VSFG) and Langmuir trough surface pressure measurements were used to investigate how the soluble surfactant perfluorooctanoic acid (PFOA) affects dipalmitoylphosphatidylcholine (DPPC) monolayers adsorbed to the air-water interface. Studies were performed as a function of PFOA concentration for DPPC surface coverages of 40 Å/monomer and 55 Å/monomer, corresponding to tightly packed and moderately packed monolayers, respectively. VSFG data showed that PFOA does not affect the structure of tightly packed DPPC monolayers, but cooperative adsorption of PFOA to moderately packed DPPC monolayers forces lipid compression, creating highly ordered acyl chains. PFOA adsorption to moderately packed DPPC monolayers also creates a charged interface, evidenced by significant intensity growth in the -OH stretching region as interfacial water is oriented by the resulting electric double layer. Interestingly, this effect is also observed for the tightly packed DPPC monolayers, implying that the surfactant adsorbs to the solvated lipid headgroups without affecting lipid chain conformation. PFOA-DPPC interactions at all DPPC surface coverages are apparent in Langmuir isotherms, where PFOA concentrations as low as 10 μM induce DPPC monolayer liftoff at 130 Å/monomer rather than ∼90 Å/monomer observed in the absence of PFOA and a monolayer collapse pressure that is ∼6 mN/m lower than that for a pure DPPC monolayer.
利用振动和频产生（VSFG）以及朗缪尔槽表面压力测量来研究可溶性表面活性剂全氟辛酸（PFOA）如何影响吸附在空气-水界面的二棕榈酰磷脂酰胆碱（DPPC）单层膜。研究是在PFOA浓度变化的情况下进行的，DPPC的表面覆盖率分别为40 Å/单体和55 Å/单体，分别对应紧密堆积和适度堆积的单层膜。VSFG数据表明，PFOA不影响紧密堆积的DPPC单层膜的结构，但PFOA对适度堆积的DPPC单层膜的协同吸附会迫使脂质压缩，形成高度有序的酰基链。PFOA对适度堆积的DPPC单层膜的吸附还会产生一个带电界面，这可通过-OH伸缩区域的显著强度增长得到证明，因为界面水会因产生的双电层而定向。有趣的是，在紧密堆积的DPPC单层膜中也观察到了这种效应，这意味着表面活性剂吸附到溶剂化的脂质头部基团上，而不影响脂质链的构象。在所有DPPC表面覆盖率下，PFOA与DPPC的相互作用在朗缪尔等温线上都很明显，其中低至10 μM的PFOA浓度会导致DPPC单层膜在130 Å/单体处脱离，而不是在没有PFOA时观察到的约90 Å/单体，并且单层膜的崩溃压力比纯DPPC单层膜低约6 mN/m。
