Rational Design of Multilayer Collagen Nanosheets with Compositional and Structural Control

Two collagen-mimetic peptides, <b>CP</b>^<b>+</b> and <b>CP</b>^<b>–</b>, are reported in which the sequences comprise a multiblock architecture having positively charged N-terminal (Pro-Arg-Gly)₃ and negatively charged C-terminal (Glu-Hyp-Gly)₃ triad extensions, respectively. <b>CP</b>^<b>+</b> rapidly self-associates into positively charged nanosheets based on a monolayer structure. In contrast, <b>CP</b>^<b>–</b> self-assembles to form negatively charged monolayer nanosheets at a much slower rate, which can be accelerated in the presence of calcium­(II) ion. A 2:1 mixture of unassociated <b>CP</b>^<b>–</b> peptide with preformed <b>CP</b>^<b>+</b> nanosheets generates structurally defined triple-layer nanosheets in which two <b>CP</b>^<b>–</b> monolayers have formed on the identical surfaces of the <b>CP</b>^<b>+</b> nanosheet template. Experimental data from electrostatic force microscopy (EFM) image analysis, zeta potential measurements, and charged nanoparticle binding assays support a negative surface charge state for the triple-layer nanosheets, which is the reverse of the positive surface charge state observed for the <b>CP</b>^<b>+</b> monolayer nanosheets. The electrostatic complementarity between the <b>CP</b>^<b>+</b> and <b>CP</b>^<b>–</b> triple helical cohesive ends at the layer interfaces promotes a (<b>CP</b>^<b>–</b>/<b>CP</b>^<b>+</b>/<b>CP</b>^<b>–</b>) compositional gradient along the <i>z</i>-direction of the nanosheet. This structurally informed approach represents an attractive strategy for the fabrication of two-dimensional nanostructures with compositional control

Structurally Ordered Nanowire Formation from Co-Assembly of DNA Origami and Collagen-Mimetic Peptides

We describe the co-assembly of two different building units: collagen-mimetic peptides and DNA origami. Two peptides <b>CP</b>^<b>++</b> and <b>sCP</b>^<b>++</b> are designed with a sequence comprising a central block (Pro-Hyp-Gly) and two positively charged domains (Pro-Arg-Gly) at both N- and C-termini. Co-assembly of peptides and DNA origami two-layer (<b>TL</b>) nanosheets affords the formation of one-dimensional nanowires with repeating periodicity of ∼10 nm. Structural analyses suggest a face-to-face stacking of DNA nanosheets with peptides aligned perpendicularly to the sheet surfaces. We demonstrate the potential of selective peptide-DNA association between face-to-face and edge-to-edge packing by tailoring the size of DNA nanostructures. This study presents an attractive strategy to create hybrid biomolecular assemblies from peptide- and DNA-based building blocks that takes advantage of the intrinsic chemical and physical properties of the respective components to encode structural and, potentially, functional complexity within readily accessible biomimetic materials

Controlling Self-Assembly of a Peptide-Based Material via Metal-Ion Induced Registry Shift

Peptide <b>TZ1C2</b> can populate two distinct orientations: a staggered (out-of-register) fibril and an aligned (in-register) coiled-coil trimer. The coordination of two cadmium ions induces a registry shift that results in a reversible transition between these structural forms. This process recapitulates the self-assembly mechanism of native protein fibrils in which a ligand binding event gates a reversible conformational transition between alternate forms of a folded peptide structure

A Supramolecular Vaccine Platform Based on α‑Helical Peptide Nanofibers

A supramolecular peptide vaccine system was designed in which epitope-bearing peptides self-assemble into elongated nanofibers composed almost entirely of α-helical structure. The nanofibers were readily internalized by antigen presenting cells and produced robust antibody, CD4+ T-cell, and CD8+ T-cell responses without supplemental adjuvants in mice. Epitopes studied included a cancer B-cell epitope from the epidermal growth factor receptor class III variant (EGFRvIII), the universal CD4+ T-cell epitope PADRE, and the model CD8+ T-cell epitope SIINFEKL, each of which could be incorporated into supramolecular multiepitope nanofibers in a modular fashion

Structurally Defined Nanoscale Sheets from Self-Assembly of Collagen-Mimetic Peptides

We report the design of two collagen-mimetic peptide sequences, <b>NSI</b> and <b>NSII</b>, that self-assemble into structurally defined nanoscale sheets. The underlying structure of these nanosheets can be understood in terms of the layered packing of collagen triple helices in two dimensions. These nanosheet assemblies represent a novel morphology for collagen-based materials, which, on the basis of their defined structure, may be envisioned as potentially biocompatible platforms for controlled presentation of chemical functionality at the nanoscale. The molecularly programmed self-assembly of peptides <b>NSI</b> and <b>NSII</b> into nanosheets suggests that sequence-specific macromolecules offer significant promise as design elements for two-dimensional (2D) assemblies. This investigation provides a design rubric for fabrication of structurally defined, peptide-based nanosheets using the principles of solution-based self-assembly facilitated through complementary electrostatic interactions

Self-Assembly of an α‑Helical Peptide into a Crystalline Two-Dimensional Nanoporous Framework

Sequence-specific peptides have been demonstrated to self-assemble into structurally defined nanoscale objects including nanofibers, nanotubes, and nanosheets. The latter structures display significant promise for the construction of hybrid materials for functional devices due to their extended planar geometry. Realization of this objective necessitates the ability to control the structural features of the resultant assemblies through the peptide sequence. The design of a amphiphilic peptide, <b>3FD-IL</b>, is described that comprises two repeats of a canonical 18 amino acid sequence associated with straight α-helical structures. Peptide <b>3FD-IL</b> displays 3-fold screw symmetry in a helical conformation and self-assembles into nanosheets based on hexagonal packing of helices. Biophysical evidence from TEM, cryo-TEM, SAXS, AFM, and STEM measurements on the <b>3FD-IL</b> nanosheets support a structural model based on a honeycomb lattice, in which the length of the peptide determines the thickness of the nanosheet and the packing of helices defines the presence of nanoscale channels that permeate the sheet. The honeycomb structure can be rationalized on the basis of geometrical packing frustration in which the channels occupy defect sites that define a periodic superlattice. The resultant 2D materials may have potential as materials for nanoscale transport and controlled release applications

Rational Design of Helical Nanotubes from Self-Assembly of Coiled-Coil Lock Washers

Design of a structurally defined helical assembly is described that involves recoding of the amino acid sequence of peptide <b>GCN4-pAA</b>. In solution and the crystalline state, <b>GCN4-pAA</b> adopts a 7-helix bundle structure that resembles a supramolecular lock washer. Structurally informed mutagenesis of the sequence of <b>GCN4-pAA</b> afforded peptide <b>7HSAP1</b>, which undergoes self-association into a nanotube via noncovalent interactions between complementary interfaces of the coiled-coil lock-washer structures. Biophysical measurements conducted in solution and the solid state over multiple length scales of structural hierarchy are consistent with self-assembly of nanotube structures derived from 7-helix bundle subunits. The dimensions of the supramolecular assemblies are similar to those observed in the crystal structure of <b>GCN4-pAA</b>. Fluorescence studies of the interaction of <b>7HSAP1</b> with the solvatochromic fluorophore PRODAN indicated that the nanotubes could encapsulate shape-appropriate small molecules with high binding affinity

Rational Design of Helical Nanotubes from Self-Assembly of Coiled-Coil Lock Washers

Design of a structurally defined helical assembly is described that involves recoding of the amino acid sequence of peptide <b>GCN4-pAA</b>. In solution and the crystalline state, <b>GCN4-pAA</b> adopts a 7-helix bundle structure that resembles a supramolecular lock washer. Structurally informed mutagenesis of the sequence of <b>GCN4-pAA</b> afforded peptide <b>7HSAP1</b>, which undergoes self-association into a nanotube via noncovalent interactions between complementary interfaces of the coiled-coil lock-washer structures. Biophysical measurements conducted in solution and the solid state over multiple length scales of structural hierarchy are consistent with self-assembly of nanotube structures derived from 7-helix bundle subunits. The dimensions of the supramolecular assemblies are similar to those observed in the crystal structure of <b>GCN4-pAA</b>. Fluorescence studies of the interaction of <b>7HSAP1</b> with the solvatochromic fluorophore PRODAN indicated that the nanotubes could encapsulate shape-appropriate small molecules with high binding affinity