Multistep Self-Assembly of the Gold-Binding Peptide AuBP1

Solid-binding peptides have emerged as a distinct class of peptides, offering significant potential for biohybrid materials technologies due to their ability to bind selectively to a specific target material and integrate different materials with bioactive molecules and their ease of biochemical and genetic conjugation with proteins. Their vast applications span health and nonmedical applications including biocatalysis, biosensing, and agriculture, as well as sustainable engineering platforms. As these applications continue to expand, it is critical to understand the optimal performance conditions of these peptides and develop a fundamental understanding of the factors controlling their binding and surface organization that lead to self-assembled properties at the material interfaces. In this work, the self-assembly of one such peptide, AuBP1 (WAGAKRLVLRRE), was revisited through atomic force microscopy (AFM) studies conducted on a Au(111) surface to gain further insight into the assembly process. Peptide film coverage on the surface was monitored as a function of adsorption time (seconds to hours) and concentration of the peptide (1 fM to 10 μM). Our analysis reveals that initial isolated peptide binding is followed by assembly into a large-scale network of clustered peptides, slower filling of the remaining sites on the surface into a uniform film, and finally reorganization of the peptide film. Our observations suggest a multistep assembly process involving both peptide-peptide and peptide-surface interactions that cooperatively influence binding transitions. We compared noncooperative and semicooperative models, which provided additional insight into the growth phase of the peptide adsorption and assembly process. Understanding real-time binding kinetics and the boundary conditions that lead to robust self-assembled peptide films could extend the utilization of material-binding peptides into future technologies.