Preparation of biomimetic surfaces that facilitate the native cellular process of peptide self-assembly
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The ability to maintain or reproduce biomolecular structures on inorganic substrates has the potential to impact diverse fields such as sensing and molecular electronics, as well as the study of biological self-assembly and structure-function relationships. Because the structure and self-assembly of biomolecules are exquisitely sensitive to their local chemical and electrostatic environment, the goal of reproducing or mimicking biological function in an abiological environment, including at a surface, is challenging. However, simple and well-characterized chemical modifications of prepared surfaces can be used to tune surface chemistry, structure, electrostatics, and reactivity of inorganic materials to facilitate biofunctionalization and function. Here, we describe the covalent attachment of 13-residue β-stranded peptides containing alkyne groups to a flat gold surface functionalized with an azide-terminated self-assembled monolayer (SAM) through a Huisgen cycloaddition, or “click,” reaction. The chemical composition and structural morphology of these surfaces were characterized using X-ray photoelectron spectroscopy (XPS), grazing incidence angle reflection-absorption infrared spectroscopy (GRAS-IR), surface circular dichroism (CD), atomic force microscopy v (AFM), and neutron reflectometry (NR). The surface-bound β-strands self-assemble into antiparallel β-sheets to form fibrillar structures 24.9 ± 1.6 nm in diameter and 2.83 ± 0.74 nm in height on the reactive surface. The results herein provide a platform for studying and controlling the self-assembly process of biomolecules into larger supermolecular structures while allowing tunable control through chemical functionalization of the surface. Interest in the mechanisms of formation of fibrillar structures have most commonly been associated with neurodegenerative diseases such as Alzheimer’s and Parkinson’s, but fibrils may actually represent the thermodynamic low-energy conformation of a much larger class of peptides and proteins. The protocol developed here is an important step towards uncovering not only the factors that dictate self- assembly, but also the mechanisms by which this fibrillar class of superstructures form.