Leila Sahebmohammadi

PhD Student
Member of the GRK2516
Group: Prof. Regine von Klitzing, TU Darmstadt Physics
Contact: E-mail

Research Project Area B: Experiments
Surface Mediated Self-assembly of Peptides

In nature, self-assembled structures give functions as in lipid membranes, proteins, or DNA. Self-assembly arises from non-covalent interactions, steric limitations, and excluded volume effects. In this project, we focus on two types of thermosensitive amphiphilic dendritic C3-symmetric peptides containing either glutamic acid or lysine. Previous research and CD spectroscopy indicate the presence of β-sheet rich self-assembled materials in phosphate buffer (PB). Additionally, investigations using QCM-D have demonstrated the formation of viscoelastic copolymer films on gold surfaces, with temperature playing a role in their adsorption and thickness. Controlled pH changes have been found to cause the depolymerization of multilayers, as observed in SPR experiments. Protonation and deprotonation processes at acidic and basic pH disrupt attractive interactions, triggering controlled depolymerization. Lysine-based comonomers exhibit stronger interactions and larger layer thickness on both silicon and gold substrates. Sequential addition of co-monomers result in the formation of stable co-polymers bound to the surface, which could be disassembled by washing with pH 2 and 12 solutions. QCM-D results show higher material adsorption on gold surfaces compared to silicon wafers at the same temperature likely due to sulfur-gold interactions. Atomic Force Microscopy suggests densely packed multilayer structures, and currently experiments using sharp cantilevers and phase imaging in AFM are performed.

Fig. 1 Surface topography of a scratched 30 double layer on Si wafer (a) height, (b) phase, and (c) magnified phase image.

Fig. 2 Surface topography of (a) pure, (b) 5 double layers, and (c) 10 double layers on Au quartz.