No abstract

Background: Functional collagen fibrils are formed through the self-assembly of collagen triple helices. Results: A designed triple helical peptide self-assembles into collagen-like mini-fibrils. Conclusion:The sequence of the triple helix alone is sufficient to "code" for the axial, periodic structure of the mini-fibrils. Significance: The work demonstrates an approach to achieve collagen-like fibrils through the self-assembly of designed triple helices.

Recently, various metal and semiconductor nanowires have been developed as building blocks for electronics, optics, and sensors. Among these newly developed nanowires, nanowires grown on biomolecular templates such as DNA and peptide assemblies are advantageous since the molecular recognition functions of these biomolecules with specific ligands can be employed to immobilize nanowires onto specific locations to establish desired device geometries. [1][2][3] However, most of the biomolecular-nanowire templates made from DNAs or peptides do not possess suitable electric properties for those devices, and therefore there is an extensive effort in the field of bionanotechnology to coat these addressable biomolecular nanowires with metals and semiconductors. [4][5][6][7][8][9][10][11][12][13][14][15][16] Recently, the morphology of coating on these peptide-nanotube templates was shown to be controlled by means of changing the peptide sequences and conformations, thus fine-tuning the electronic structures of resulting nanowires for their device applications. [17][18][19] While these biomolecular-nanowire templates appear to be promising building blocks for nanodevices, it is essential to have size monodispersity, strength, and mass producibility to impact real-world applications. For example, biomolecular templates self-assembled from peptidic monomers tend to yield polydisperse materials with heterogeneous diameters and uncontrolled length through the self-assembly process. The tobacco mosaic virus (TMV), a rod-shaped biomolecular template, has been applied for various metal coatings, however accurate control of the length with low dispersity is not an easy task. [20,21] The other type-DNA biomolecular templates-have defined lengths determined by the number of nucleic acids, however they lack conformational rigidity. The tendency of supertwisting of the double-helix DNA structure makes it difficult to obtain rigid and straight nanowires. Their production cost and time may also not be suitable for large-scale syntheses.Herein we report a new application using a collagen-like triple helix as a template nanowire which appears to overcome some of the shortcomings of other biomolecular templates. The collagen-like triple helix is the genetically engineered polypeptide assembly that contains a fragment from the natural collagen sequence. Our study demonstrates that by using the recombinant technology, we can design and amplify a collagen-like triple helix that is monodisperse, easily mineralized with metal ions, and can, thus, be applied as rigid biomolecular templates for metal-nanowire fabrications. Collagens are the major components of extracellular matrices for bones, cartilages, skins, blood vessels, and corneas, and they are the most abundant proteins in higher organisms with superior mechanical properties. [22][23][24] The collagen-like triple helix is made of three polypeptide chains tightly twisted and bundled together to form a rigid, rod-shaped molecule that is suitable for applications in building blocks of nanod...