A time domain study of surfactin penetrating a phospholipid monolayer at the air-water interface investigated using sum frequency generation spectroscopy, infrared reflection absorption spectroscopy, and AFM-nano infrared microscopy
A time domain study of surfactin penetrating a phospholipid monolayer at the air-water interface investigated using sum frequency generation spectroscopy, infrared reflection absorption spectroscopy, and AFM-nano infrared microscopy
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DOI：
10.1016/j.bbamem.2019.06.004
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发表时间：
2019-09-01
影响因子：
3.4
通讯作者：
Davies, P. B.
中科院分区：
文献类型：
--
作者：
Goussous, S. A.;Fellows, A. P.;Davies, P. B.
我们用非线性和频(SFG)振动光谱和红外反射吸收光谱(IRRAS)研究了表面活性剂与1，2-二棕榈酰甘油-3-磷胆碱(DPPC)单分子膜在空气-水界面的相互作用随时间的变化。通过选择性重氢反应，区分了磷脂和表面蛋白的SFG共振。同时测量界面上的表面压力达8h，经过一段诱导期后，脂质的光谱逐渐减弱，表面素的光谱逐渐出现，同时表面压力增加。然而，最终表面蛋白信号消失了，而脂质信号又出现了。尽管脂质的SFG光谱在中间时间消失，但脂质的IRRAS光谱始终存在于界面处。改变亚相的pH值、脂类的初始表面压力和表面活性物质的浓度，研究了SFG的时间行为的变化。在选定的时间沿时间分布将表面膜样品转移到云母基片上，并用原子力显微镜-纳米红外光谱(Nano-IR)进行成像。提出了一个模型来解释使用的四种不同实验技术的结果。
We have investigated the interaction of surfactin with a monolayer of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at the air-water interface as a function of time, following its injection into the sub-phase, using non-linear Sum Frequency Generation (SFG) vibrational spectroscopy and Infrared Reflection Absorption Spectroscopy (IRRAS). SFG resonances from the phospholipid and from the surfactin were distinguished from each other by using selective deuteration. The surface pressure at the interface was measured concurrently for up to 8 h. After an induction period, the spectra from the lipid diminished and those of surfactin gradually appeared whilst at the same time the surface pressure increased. However, eventually the surfactin signals disappeared and those of the lipid reappeared. Although the SFG spectra of the lipid disappeared at intermediate times, the IRRAS spectra of the lipid were always present at the interface. Variation in the temporal SFG behaviour was investigated as the pH of the sub-phase, the initial surface pressure of the lipid, and the surfactin concentration were changed. Samples of the surface film were transferred onto mica substrates at selected times along the temporal profile and imaged by Atomic Force Microscopy - nano Infrared Spectroscopy (nano-IR). A model is proposed to account for the results from the four different experimental techniques used.