Small and Large, Charged Molecules in Solution and at Interfaces

Sammanfattning: The influence of small and large, charged molecules on the properties of aqueous interfaces has important implications in chemistry, biology, and medicine. For example, at the surface of marine aerosols, the presence of halide anions and tropospheric gases gives way to multiphase chemical reactions affecting climate and air quality. In this Thesis, we investigate three different systems and phenomena at the interface using molecular simulations, experiments, and theory.A new accurate all-atom force field is developed to study thiocyanate ions in solution and at the interface. We show how different cations affect the properties of NaSCN and KSCN bulk aqueous solutions and, supplementing vibrational sum frequency spectroscopy, our simulations indicate that the thiocyanate anion has a higher affinity for hydrophobic surfaces with exposed methyl groups than for the air−water interface.Combining coarse-grained simulations and quartz crystal microbalance with dissipation monitoring experiments, we develop an analytical model to study the adsorption of amyloid fibrils onto oppositely charged lipid bilayers. The model shows that short, rigid fibrils adsorb more onto oppositely charged surfaces than long fibrils.A computationally efficient coarse-grained model is developed to investigate the interaction of cationic peptides with lipid membranes. Additionally, we use small-angle X-ray scattering experiments and all-atom simulations to study the solution behavior of arginine-rich cell-penetrating peptides. Despite their large positive charge, we find that arginine decapeptides self-associate in aqueous solution. We elucidate the molecular origin of the attraction, and highlight its common occurrence in protein crystal structures.