Biological Physics Group, Schuster Building, Oxford Road, the University of Manchester, Manchester, M13 9PL, UK.
Langmuir. 2010 Apr 20;26(8):5690-6. doi: 10.1021/la9037952.
Short peptide surfactants have recently emerged as a new class of amphiphiles, with tremendous potential in improving surface biocompatibility and mediating interfacial DNA immobilization. To establish their basic interfacial adsorption properties, cationic peptide surfactants V(m)K(n) have been studied by combining the measurements of spectroscopic ellipsometry (SE), neutron reflection (NR) and atomic force microscopy (AFM). Our results showed that changes in peptide structure, concentration, solution pH and ionic strength all affected their interfacial assembly. Increases in m and decreases in n reduced the critical aggregation concentration (CAC), but increased the amount of adsorption, showing the strong influence of the amphiphilic balance between hydrophilic and hydrophobic moieties. While the surface adsorbed amount increased with time and peptide concentration, an increase in ionic strength decreased peptide adsorption due to surface charge neutralization. Changes in solution pH did not affect the equilibrium surface adsorbed amount on the weakly negative SiO(2) surface, but did alter the adsorption dynamics. Neutron reflection revealed that V(6)K readily formed a bilayer structure of 35 A thickness at the interface, with the main part of the V(6) fragments being packed back-to-back to form a 15 A hydrophobic core and the two outer K regions being incorporated with a minor amount of V fragments forming the headgroup layers of 9 A each. AFM imaging revealed a sheet-like membrane structure incorporating defects of holes but the thicknesses probed by AFM were consistent with neutron reflection. It was demonstrated that the V(6)K peptide bilayer was effective for immobilization of DNA. The amount of DNA immobilized followed approximate 1:1 charge neutralization between the outer leaf peptide sublayer and the negatively charged DNA.
短肽表面活性剂作为一类新型两亲分子，在改善表面生物相容性和介导界面 DNA 固定化方面具有巨大的潜力。为了建立它们的基本界面吸附特性，通过光谱椭圆测量（SE）、中子反射（NR）和原子力显微镜（AFM）的结合，研究了阳离子肽表面活性剂 V(m)K(n)。我们的结果表明，肽结构、浓度、溶液 pH 值和离子强度的变化都影响其界面组装。m 的增加和 n 的减少降低了临界聚集浓度（CAC），但增加了吸附量，表明亲水性和亲脂性部分之间的两亲平衡具有强烈的影响。虽然表面吸附量随时间和肽浓度的增加而增加，但离子强度的增加由于表面电荷中和而降低了肽的吸附。溶液 pH 值的变化不会影响弱负 SiO(2)表面上的平衡表面吸附量，但会改变吸附动力学。中子反射表明，V(6)K 容易在界面上形成 35 A 厚的双层结构，其中 V(6)片段的主要部分背对背排列形成 15 A 的疏水性核心，两个外部 K 区域与少量 V 片段结合形成每个 9 A 的头部层。原子力显微镜成像显示了一种包含孔缺陷的片状膜结构，但原子力显微镜探测到的厚度与中子反射一致。结果表明，V(6)K 肽双层对 DNA 的固定化是有效的。固定化的 DNA 量遵循外层肽亚层和带负电荷的 DNA 之间的近似 1:1 电荷中和。
