Potassium Ion Mediated Double‐Layered Upright Assembly of Negatively Charged Amyloid‐Like Peptides at Mica/Water Interface

Abstract Insight into the surface‐assisted self‐assembly of amyloid‐like peptides is essential to the design and fabrication of novel functional nanomaterials as well as to uncovering the pathogenesis of various neurodegenerative diseases. Despite extensive research, how to control the self‐assembly of amyloid‐like peptides effectively remains challenging. Here, through a combined experimental and theoretical approach, it is demonstrated that cations could modulate the mica/water interface and further induce the self‐assembly of the negatively charged amyloid‐like peptide Ac–VGGAVVAGV–COO⁻ (Ac–GAV–9) into multilayered nanofilaments with a surprising all‐upright parallel β‐sheet conformation. In particular, highly ordered double‐layered nanofilaments are observed on the negatively charged mica surfaces in the presence of 0.5–1.5 m KCl. The molecular dynamics simulations further reveal that the double‐layered nanofilaments have intriguing parallel β‐sheet structures with the C‐termini of the first parallel monolayer pointing to the mica surface and the C‐termini of the second parallel monolayer pointing to the solvent. Moreover, the stability of the nanofilaments could be modulated by peptide and ion concentrations. Further studies show that the growth of double‐layered fibrils at the mica/water interface is a common phenomenon for Ac–GAV–9 in the presence of a variety of salt types.