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  1. Abstract

    Peptide self‐assembly is fast evolving into a powerful method for the development of bio‐inspired nanomaterials with great potential for many applications, but it remains challenging to control the self‐assembling processes and nanostrucutres because of the intricate interplay of various non‐covalent interactions. A group of 28‐residue α‐helical peptides is designed including NN, NK, and HH that display distinct hierarchical events. The key of the design lies in the incorporation of two asparagine (Asn) or histidine (His) residues at theapositions of the second and fourth heptads, which allow one sequence to pack into homodimers with sticky ends through specific interhelical Asn‐Asn or metal complexation interactions, followed by their longitudinal association into ordered nanofibers. This is in contrast to classical self‐assembling helical peptide systems consisting of two complementary peptides. The collaborative roles played by the four main non‐covalent interactions, including hydrogen‐bonding, hydrophobic interactions, electrostatic interactions, and metal ion coordination, are well demonstrated during the hierarchical self‐assembling processes of these peptides. Different nanostructures, for example, long and short nanofibers, thin and thick fibers, uniform metal ion‐entrapped nanofibers, and polydisperse globular stacks, can be prepared by harnessing these interactions at different levels of hierarchy.

     
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  2. Abstract

    Controlling the diameters of nanotubes represents a major challenge in nanostructures self‐assembled from templating molecules. Here, two series of bolaform hexapeptides are designed, with Set I consisting of Ac‐KI4K‐NH2, Ac‐KI3NleK‐NH2, Ac‐KI3LK‐NH2and Ac‐KI3TleK‐NH2, and Set II consisting of Ac‐KI3VK‐NH2, Ac‐KI2V2K‐NH2, Ac‐KIV3K‐NH2and Ac‐KV4K‐NH2. In Set I, substitution for Ile in the C‐terminal alters its side‐chain branching, but the hydrophobicity is retained. In Set II, the substitution of Val for Ile leads to the decrease of hydrophobicity, but the side‐chain β‐branching is retained. The peptide bolaphiles tend to form long nanotubes, with the tube shell being composed of a peptide monolayer. Variation in core side‐chain branching and hydrophobicity causes a steady shift of peptide nanotube diameters from more than one hundred to several nanometers, thereby achieving a reliable control over the underlying molecular self‐assembling processes. Given the structural and functional roles of peptide tubes with varying dimensions in nature and in technological applications, this study exemplifies the predictive templating of nanostructures from short peptide self‐assembly.

     
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