摘要

用计时电位法、偏振调制红外反射吸收光谱法（PM-IRAS）对最近发现的细菌素样肽BACSP222在金电极上的脂质模型系统中的行为、二级结构和取向进行了研究，并对其进行了衰减。TAL反射红外（ATR—IR）光谱。红外光谱表明，BaBSP222的二级结构主要为α-螺旋结构。对酰胺I区的光谱分析表明，该肽的α-螺旋片段被插入双层中，在双层膜稳定且附着于Au（111）表面的电位范围内，即从0.5到0.3 V与Ag/AgCl。BACSP222向膜的插入显著改变脂质分子的酰基链的构象，从全反式到部分熔融；然而，链变得不太倾斜。基于这些结果，我们建议BaBSP222与筒状壁孔形成相互作用的DMPC双层。在该模型中，BACSP222的α-螺旋插入到膜中，α-螺旋轴与膜法线之间的夹角等于18°。肽的α-螺旋片段的取向变化表明，BaBSP222相对于双层表面的取向是潜在的依赖性。该肽被插入到由金属表面负电荷产生的静电场驱动的膜中。它不插入负电位，膜脱离金属，不再暴露于金属的静电场。

The behavior, secondary structure, and orientation of a recently discovered bacteriocin-like peptide BacSp222 in a lipid model system supported at a gold electrode was investigated by chronocoulometry, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and attenuated total reflectance infrared (ATR-IR) spectroscopy. The IR spectra show that the secondary structure of BacSp222 is predominantly α-helical. Analysis of the spectra in the amide I region shows that the α-helical fragment of the peptide is inserted into bilayer at the potential range at which the bilayer is stable and attached to the Au(111) surface, i.e., from −0.5 to 0.3 V vs Ag/AgCl. Insertion of BacSp222 to the membrane significantly changes the conformation of the acyl chains of lipid molecules, from all-trans to partially melted; however, the chains become less tilted. Based on these results, we propose that BacSp222 interacts with the DMPC bilayer through the barrel-stave pore formation. In this model, α-helix of BacSp222 inserts into the membrane with an angle between the α-helix axis and membrane normal equal to ∼18°. The changes in orientation of the α-helical fragment of the peptide indicate that the orientation of BacSp222 with respect to the bilayer surface is potential-dependent. The peptide is inserted into the membrane driven by the electrostatic field generated by negative charge at the metal surface. It is not inserted at negative potentials where the membrane is detached from the metal and no longer exposed to the electrostatic field of the metal.

https://pubs.acs.org/doi/abs/10.1021/acs.langmuir.5b04741