Controlling the Diameters of Nanotubes Self‐Assembled from Designed Peptide Bolaphiles

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‐NH2 and Ac‐KI3TleK‐NH2, and Set II consisting of Ac‐KI3VK‐NH2, Ac‐KI2V2K‐NH2, Ac‐KIV3K‐NH2 and 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.

Nanoribbons self-assembled from short peptides demonstrate the formation of polar zippers between β-sheets

“…Small-angle neutron scattering (SANS) allows us to undertake in situ measurements of the self-assembled nanostructures in solution at length scales typically below 100 nm with statistical significance 16 – 21 . In SANS measurements, the intensity of neutron scattering, I ( q ), is recorded as a function of the scattering vector modulus q (Fig.…”

“…In spite of a poor fit at the intermediate q range from 0.07 to 0.2 Å −1 , such a model fit could approximate the main structural parameters of Ac-I 3 QGK-NH 2 nanoribbons, giving a minor radius of 4.2 nm, an axial ratio of 4.8, and a length of more than 100 nm (Table 1 and Supplementary Table 1 ). Note that the model fitting was insensitive to dimensions of more than 100 nm because the scattering data did not extend to sufficiently low values of q 20 , 21 . The combination of two elliptical cylinders (ECM1 + ECM2) with different parameters was found to significantly improve the fitting quality (denoted as the blue line in Fig.…”

“…SANS experiments were performed on the SANS2D and LOQ diffractometers at the ISIS Pulsed Neutron Source (Rutherford Appleton Laboratory, (Didcot, UK) at 25 °C 21 , 41 ( http://isis.stfc.ac.uk ). In brief, the 8 or 16 mM peptide solutions were prepared by directly dissolving peptides in D 2 O, followed by slightly adjusting the solution pD to 7.0 with dilute NaOD solution.…”

Ordered Nanofibers Fabricated from Hierarchical Self‐Assembling Processes of Designed α‐Helical Peptides

“…Small Angle Neutron Scattering: SANS experiments were performed on the LOQ diffractometer at the ISIS Pulsed Neutron Source (Rutherford Appleton Laboratory, Didcot, UK) as previously described. [71] Peptide solutions for the measurement were prepared in D 2 O and pipetted into 2.0 mm path-length disc-shaped fused-silica cuvettes. The cuvettes were in turn mounted on a computer-controlled sample changer.…”

Designing stable, hierarchical peptide fibers from block co-polypeptide sequences

“…6 A wide range of strategies exist for creating peptide based selfassembled materials including: dipeptides, 7 dynamic peptide libraries, 8 spider-silk based sequences, 9 peptide amphiphiles (PA) 10,11 and block co-polypeptides (BCPP). 12,13 These amphiphilic peptide materials have been shown to organize into various morphologies, such as; spherical-, [14][15][16][17] and cylindrical micelles, 6,8,18 vesicles, 12,17,[19][20][21] nanotubes, [22][23][24][25][26][27][28][29][30] nanoribbons, 25,[30][31][32][33][34] and hydrogel networks. 13,35 Nanotubes are dened as well-dened hollow cylinders with a diameter range of 0.5-500 nm and an aspect exceeding ve.…”