Research ArticleMATERIALS SCIENCE

Tuning peptide self-assembly by an in-tether chiral center

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Science Advances  11 May 2018:
Vol. 4, no. 5, eaar5907
DOI: 10.1126/sciadv.aar5907
  • Fig. 1 Study of BDCP peptides self-assembly.

    (A) Molecular structure of cyclic pentapeptides of Ac-CAAAS5(X)-NH2 (BDCPs). (B) Simulated structure of helical BDCP-1-R peptide in water. Figure was adapted from our previous article (24). (C) Table of peptides tested for self-assembly in H2O, where “√” and “−” indicate self-assembly was achieved or not achieved, respectively. [a] S and R represents the absolute configuration of the in-tether chiral center in the peptide epimer, and L denotes the peptide is an uncyclized linear peptide (structural details in the Supplementary Materials). (D) SEM images of self-assembled BDCP-1-R at various magnifications (images 1 to 5) and BDCP-2-R (image 6). Image 4 is a high-magnification SEM image of the region inside the yellow box in image 1, indicating rectangular cross section. Scale bars, 1 μm (upper left), 3 μm (upper middle), 500 nm (upper right), 200 nm (lower left), 15 μm (lower middle), and 5 μm (lower right).

  • Fig. 2 Characterization of BDCP-1-R peptide nanomaterials.

    TEM image (A), electron diffraction pattern (B), and XRD pattern (C) of BDCP-1-R peptide nanomaterials. The labels contained a star “*” indicate the diffraction peaks of BDLP-1-R peptide nanomaterials. (D) AFM images of the peptide nanomaterials (1) and peptide nanodots (3). Three-dimensional views of (1) and (3) are shown in (2) and (4), respectively. Sectional height plots along the labeled arrows in (1) and (3) are shown on the right.

  • Fig. 3 Characterization of self-assembly behavior in BDCP-1-R nanomaterials.

    (A) FTIR spectrum of the amide bond bands and hydrogen bond region (inset) and (B) Raman spectrum of BDCP-1-R peptide nanomaterials. (C) UV-vis spectra of BDCP-1-R monomers (black line) and peptide nanomaterials (blue dashed line). a.u., arbitrary units. (D) Fluorescence spectra of BDCP-1-R monomers (dashed lines) and peptide nanomaterials (solid lines) dissolved or dispersed in water (1 mg/ml, 20°C). Peptide nanomaterial peaks are broader and red-shifted. (E) Optical image of BDCP-1-R peptide nanomaterials and associated fluorescence images with visible luminescence using UV-blue, blue-green, and green-red filters.

  • Fig. 4 Elucidation of BDCP-1-R nanostructure packing model.

    (A) Predicted crystallite packing of BDCP-1-R molecules. (B) Nonpolar region formed by the aromatic-aromatic and aromatic-sulfur interactions of the side-chain tethers. (C) Polar region formed by hydrogen bonding of the α-helical backbones. Carbon atoms in different molecules are shown in different colors. In all the structures, N/O/S atoms are in blue/red/yellow, respectively, and nonpolar hydrogen atoms are omitted for clarity.

  • Fig. 5 CIH peptide assembly is tolerant of amino acid mutations.

    (A) Molecular structures of BDCP-3(R/S) and BDCP-4(R/S). Side chains of middle amino acids are labeled in blue. (B) SEM images of self-assembled BDCP-3-R and BDCP-4-R. (C) CD spectra of BDCP-3/4-R/S in water (pH 7, 20°C, and 100 μM). (D) FTIR spectra of BDCP-3-R and BDCP-4-R. Wavenumbers of peaks in pink circles are given.

  • Fig. 6 Characterization of peptide nanostructures as supercapacitors.

    (A) Cyclic voltammograms at different scan rates for BCDP-1-R. (B) Galvanostatic charge-discharge curves of BDCP-1-R at different current densities. (C) Cycle stability of BDCP-1-R electrode at a scan rate of 0.4 mV/s with 5000 cycles. (D) CV curves for peptides BDCP-1-R through BDCP-4-R at a scan rate of 10 mV/s. (E) Areal capacitances as functions of current density. (F) Comparison of reported peptide-based supercapacitors. a, areal capacitance of BDCP-4-R at 50 μA/cm2; b, areal capacitance of BDCP-2-R at 50 μA/cm2.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/5/eaar5907/DC1

    Synthesis of BDCP peptides

    LC-MS, mass, and 1H and 13C spectra for nonnatural amino acids or peptides

    BDCP-2-S/R

    BDCP-3-S/R

    BDCP-4-S/R

    Nuclear magnetic resonance data of unnatural amino acids

    1H of Fmoc-S5(2-Me)-OH

    13C of Fmoc-S5(2-Me)-OH

    High-resolution mass spectrum

    1H of Fmoc-S5(2-Ph)-OH

    13C of Fmoc-S5(2-Ph)-OH

    High-resolution mass spectrum

    1H of Fmoc-S5(2-naphnal)-OH

    fig. S1. CD spectra of BDCP-0/1/2/-R or S in water, respectively.

    fig. S2. Simulated powder XRD pattern from the predicted crystal structure of BDCP-1-R.

    fig. S3. Morphology of the BDCP-1-R nanostructure on GC electrode.

    fig. S4. Electrochemical performance of the BDCP-2/3/4-R peptide assemblies.

    fig. S5. Electrochemical performance of BDCP-1-R nanostructures in different electrolytes.

    table S1. Relationship between peptide structures and self-assemblies.

    cif file

  • Supplementary Materials

    This PDF file includes:

    • Synthesis of BDCP peptides
    • LC-MS, mass, and 1H and 13C spectra for nonnatural amino acids or peptides
    • BDCP-2-S/R
    • BDCP-3-S/R
    • BDCP-4-S/R
    • Nuclear magnetic resonance data of unnatural amino acids
    • 1H of Fmoc-S5(2-Me)-OH
    • 13C of Fmoc-S5(2-Me)-OH
    • High-resolution mass spectrum
    • 1H of Fmoc-S5(2-Ph)-OH
    • 13C of Fmoc-S5(2-Ph)-OH
    • High-resolution mass spectrum
    • 1H of Fmoc-S5(2-naphnal)-OH
    • fig. S1. CD spectra of BDCP-0/1/2/-R or S in water, respectively.
    • fig. S2. Simulated powder XRD pattern from the predicted crystal structure of BDCP-1-R.
    • fig. S3. Morphology of the BDCP-1-R nanostructure on GC electrode.
    • fig. S4. Electrochemical performance of the BDCP-2/3/4-R peptide assemblies.
    • fig. S5. Electrochemical performance of BDCP-1-R nanostructures in different electrolytes.
    • table S1. Relationship between peptide structures and self-assemblies.

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