Nanoscale organisation of water and ions at bio-interfaces: consequences on anti-infective peptide adsorption

最近的研究结果表明，水和简单的金属离子可以自发地在溶液中的矿物表面产生相关的有序网络。基于原子力显微镜（AFM）的初步结果表明，类似的效果发生在表面的脂质双层。由于生物界面的柔软性，有序界面水/离子结构的存在对于调节生物膜的力学性质、形状和局部流动性具有深刻的意义。它也将有影响，在介导的膜结合分子，如生物标志物，药物和肽的相互作用，并在bioenergetics.This建议利用最近的进展，在该领域的AFM探索的局部结构之间的相互作用的界面液体（水和离子）和模型膜的行为时，经历相变。该研究将通过AFM在溶液中进行，并具有分子或单个水合离子的精度。结果将提供界面液体结构的亚纳米图，当膜经历凝胶到流体的转变时，局部跟踪它们的演变，建立它们对膜性质（弹性，流动性）的影响，并量化它们在介导抗侵袭肽的吸附中的影响。在该项目的第一部分中，将通过原子力显微镜对双层表面的特定区域进行成像和探测（机械性能映射），同时使用精确的环境控制器逐渐增加溶液的温度。将在整个过程中监测熔融膜和界面离子结构彼此之间的相互作用，包括随后冷却膜时。拟议的研究检查参数的影响，如膜脂质成分和存在于溶液中的离子类型对界面结构的形成和演变。还将研究涉及不同脂质的二元混合物的界面，以阐明膜的物理和化学奇异性（如域边缘）对界面过程所起的作用。随后，将在生物相关条件下研究界面效应对膜结合肽的影响。将在已知插入膜中的抗微生物/抗感染肽（时间蛋白）存在下进行实验。目标是确定在该项目的前几个阶段观察到的界面效应是否会影响抗菌肽和膜之间的纳米级相互作用，特别是单肽的结合和随后的插入。将仔细监测该过程，从凝胶相膜（无插入）到流体膜，特别注意插入肽的空间位置和与先前界面奇点的潜在时间相关性。该项目的研究结果将是非常新颖的，很可能提供第一个直接观察生物界面的界面介导的过程。

Recent findings have shown that water and simple metal ions can spontaneously create correlated, ordered networks at the surface of minerals in solution. Preliminary results based on atomic force microscopy (AFM) suggest that similar effects occur at the surface of lipid bilayers. Due to the soft nature of biointerfaces, the existence of ordered interfacial water/ion structures would have deep implications for regulating biomembranes' mechanical properties, shape and local fluidity. It would also have implications in mediating the interactions of membrane-binding molecules such as biomarker, drugs and peptides, and for charge transfer in bioenergetics.This proposal exploits recent advances in the field of AFM to explore the interplay between the local structure of the interfacial liquid (water and ions) and the behaviour of model membranes when undergoing a phase transition. The study will be conducted by AFM in solution and with molecular or single hydrated ion precision. The results will provide sub-nanometre maps of interfacial liquid structures, track their evolution locally as the membrane undergoes a gel to fluid transition, establish their influence on the membrane properties (elasticity, fluidity), and quantify their implications in mediating the adsorption of anti-invective peptides. In the first part of the project, specific regions of the bilayer surface will be imaged and probed (mechanical properties mapping) by AFM while the temperature of the solution is progressively increased using a precise environment controller. The mutual effect that the melting membrane and the interfacial ionic structures have on each other will be monitored throughout the process, including upon subsequent cooling of the membrane. The proposed research examines the influence of parameters such as membrane lipid composition and the type of ions present in the solution on the formation and evolution of interfacial structures. Interfaces involving binary mixtures of dissimilar lipids will also be studied in order elucidate the role played by membrane physical and chemical singularities such as domain edges on interfacial processes.Subsequently, the influence of interfacial effects on membrane-binding peptides will be studied in biologically relevant conditions. Experiments will be conducted in the presence of antimicrobial/anti-infective peptides (Temporins) known to insert into the membrane. The goal will be to determine whether the interfacial effects observed in the previous phases of the project can influence the nanoscale interactions between antimicrobial peptides and membranes, in particular the binding and subsequent insertion of single peptides. The process will be carefully monitored, starting from gel-phase membranes (no insertion) to fluid membranes, paying particular attention to the spatial location of inserting peptides and a potential temporal correlation with a prior interfacial singularity. The findings of this project will be highly novel and are likely to provide the first direct observation of interface-mediated processes at biointerfaces.