Molecular Engineering of Peptide-Inorganic Interfaces: From Aqueous Conformations to Complex Surface Assemblies

Thesis (Ph.D.)--University of Washington, 2020Bio-inorganic interfaces, in which biomolecules intimately contact inorganic materials, have become the centerpiece for advanced technologies in medicine, catalysis, and electronics. Considering the convolutional complexity of interfaces involving environmental conditions and biomolecular and inorganic surface intricacies, it is of utmost importance to obtain a fundamental understanding of molecular conformations, interactions, and hybrid interfacial properties. Based on such basic understanding, it becomes feasible to engineer molecules with the tailored ability to spontaneously build-up, via self-assembly, a bio-inorganic interface with desired device relevant properties. It has been recognized in this Thesis that solid-binding peptides are suited perfectly for this molecular engineering task due to their vast sequence space, labile conformational nature, and reliance on soft intermolecular interactions that can be fine-tuned through environmental controls, and ability to form long-range ordered structures. Here, solid-binding peptides designed to bind and assemble on graphite surfaces are interrogated using scanning probe microscopy techniques and molecular dynamics simulations to explore and control their self-assembly pathway. Thermal selection of peptide conformations is shown to direct the long-range ordering of peptides at graphite surfaces. Through energetic analysis of peptide-graphite interactions, using a technique dubbed Intrinsic Friction Analysis, the molecular implications of thermal conformational selection are elucidated and used to rationally design a peptide with tailored binding energy and assembly structure. The impacts of these thermally selected conformations on electron transport across the bio-inorganic interface are interrogated via scanning tunneling spectroscopy and metadynamics, revealing control over device relevant properties. Peptide-substrate recognition is explored using atomic resolution microscopy to understand peptide miscibility and nucleation in binary assemblies. Finally, the role of lateral confinement on self-assembly is explored, revealing unexpected peptide adsorption and assembly phenomena enabling tailored self-assembly at various length scales. From these fundamental insights, novel bio-inorganic devices can be rationally designed for targeted technological applications