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

最近的发现表明，水和简单的金属离子可以自发地在溶液中的矿物表面形成相互关联的有序网络。基于原子力显微镜(AFM)的初步结果表明，类似的效应也发生在脂质双层的表面。由于生物界面的柔软性质，有序界面水/离子结构的存在将对调节生物膜的力学性能、形状和局部流动性产生深远的影响。它还将在调节生物标记物、药物和多肽等膜结合分子的相互作用以及生物能量中的电荷转移方面具有重要意义。该提议利用AFM领域的最新进展来探索界面液体(水和离子)的局部结构与模型膜在相变时的行为之间的相互作用。这项研究将由原子力显微镜在溶液中进行，并以分子或单一水合离子的精度进行。这些结果将提供界面液体结构的亚纳米图，跟踪它们在膜经历凝胶到流体转变时的局部演变，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性多肽吸附方面的意义。在该项目的第一部分，将通过AFM成像和探测双层表面的特定区域(机械特性图)，同时使用精确的环境控制器逐步提高溶液的温度。在整个过程中，将监测熔融膜和界面离子结构对彼此的相互影响，包括在膜随后冷却时。这项拟议的研究考察了膜脂组成和溶液中存在的离子类型等参数对界面结构形成和演化的影响。此外，还将研究不同脂类二元混合物的界面，以阐明膜物理和化学奇异性(如结构域边)对界面过程的影响。随后，将在生物相关的条件下研究界面效应对膜结合肽的影响。实验将在已知插入膜中的抗微生物/抗感染多肽(Temporins)的存在下进行。目标是确定项目前几个阶段中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。将仔细监测这一过程，从凝胶相膜(未插入)到流体膜，特别注意插入多肽的空间位置以及与先前界面奇异性的潜在时间关联。这个项目的发现将是非常新颖的，并可能提供第一次直接观察到生物界面上的界面中介过程。

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.