Shear Alignment of Bola-Amphiphilic Arginine-Coated Peptide Nanotubes

Abstract

The bola-amphiphilic arginine-capped peptide RFLRF self-assembles into nanotubes in aqueous solution. The nanostructure and rheology are probed by in situ simultaneous rheology/small-angle scattering experiments including rheo-SAXS, rheo-SANS, and rheo-GISANS (SAXS: small-angle X-ray scattering, SANS: small-angle neutron scattering, GISANS: grazing incidence small-angle neutron scattering). Nematic alignment of peptide nanotubes under shear is observed at sufficiently high shear rates under steady shear in either Couette or cone-and-plate geometry. The extent of alignment increases with shear rate. A shear plateau is observed in a flow curve measured in the Couette geometry, indicating the presence of shear banding above the shear rate at which significant orientation is observed (0.1-1 s). The orientation under shear is transient and is lost as soon as shear is stopped. GISANS shows that alignment at the surface of a cone-and-plate cell develops at sufficiently high shear rates, very similar to that observed in the bulk using the Couette geometry. A small isotope effect (comparing HO/DO solvents) is noted in the CD spectra indicating increased interpeptide hydrogen bonding in DO, although this does not influence nanotube self-assembly. These results provide new insights into the controlled alignment of peptide nanotubes for future applications.

Self‐assembled chiral nanostructures of amphiphilic peptide: from single molecule to aggregate

“…Chemical structure and molecular model of A 6 R 1 (NH 2 ─AAAAAAR─COOH) are described in Figure . Six consecutive alanine residues are selected as the hydrophobic tail , and a positively charged arginine with large guanidine group acts as the hydrophilic head . The length of A 6 R 1 is approximately 2.96 nm (Figure ).…”

“…The single molecular and aggregated level evidences in this work will shed light on the understanding of the hierarchical chiral self‐assembly pathway and the underlying mechanism. In other aspect, self‐assembled amphiphilic peptide nanostructures have been considered not only as pathological aggregates but also as advanced materials in material sciences , such as for biocatalyst , stabilizing diverse membrane as a fundamental component . The final function of peptides depends on the self‐assembled and properties of hierarchical structures, the mechanisms of peptide aggregation (the driving forces needed to understand) .…”

“…Short cationic peptides rich in arginine have capable of traversing the plasma membranes of eukaryotic cells and antimicrobial activities . Arginine contains a guanidinium group that adopts a planar Y‐shape with delocalizing cationic charge, which can form bidentate hydrogen bonds with phosphates in lipid as well as electrostatic interactions . The bioactivity of arginine‐based peptides was afforded by the special sequences of amino acids and the aggregation structures.…”

“…The bioactivity of arginine‐based peptides was afforded by the special sequences of amino acids and the aggregation structures. A formidable challenge in optimizing and harnessing the properties of assemblies is to gain insight into architectures and to elucidate precisely how assembled structures is constructed from peptide molecules . We designed a model system that enables the self‐assembly of arginine‐based amphiphilic peptides to be controlled in a systematic manner as a function of the hydrophilic peptide region (A 6 R 1 , A 6 R 3 , A 6 R 5 , A 6 R 6 , and A 6 R 8 ).…”

Isotopic Control over Self-Assembly in Supramolecular Gels

“… 8 Slight differences in dimensions have been reported for nanotubes formed from a small peptide in H 2 O or D 2 O. 9 For biopolymer-based gels, the melting temperature of gelatin gels is higher in D 2 O as compared to H 2 O, 10 and the gels are more rigid in D 2 O. Similarly, agar-based gels have a higher modulus in D 2 O compared to H 2 O, 11 as do κ-carrageenan-based gels.…”