Alpha helical surfactant-like peptides self-assemble into pH-dependent nanostructures

Area of Science:

• Biomaterials Science
• Supramolecular Chemistry
• Nanotechnology

Background:

• Peptides can self-assemble into various nanostructures.
• Controlling peptide self-assembly is crucial for designing functional nanomaterials.
• Surfactant-like peptides offer a simple model for studying self-assembly.

Purpose of the Study:

• To investigate the pH-dependent self-assembly properties of a designed surfactant-like peptide, R3L12.
• To elucidate the structural basis of the observed pH-dependent morphological and conformational changes.
• To explore the potential applications of this peptide's unique self-assembly behavior.

Main Methods:

• Cryogenic-transmission electron microscopy (cryo-TEM) for high-resolution structural imaging.
• Small-angle X-ray scattering (SAXS) to determine overall structure and conformational changes.
• Circular dichroism (CD) and Fourier-transform infrared (FTIR) spectroscopy to analyze secondary structure and side-chain ordering.

Main Results:

• Peptide R3L12 self-assembles into "cross-α" nanotubes with α-helical conformation at pH 9 and below.
• At higher pH, near the arginine pKa, the peptide forms decorated vesicular aggregates.
• Spectroscopic data indicate a loss of α-helical and leucine side-chain ordering in vesicular structures, suggesting a lipid-raft-like phase separation.

Conclusions:

• The surfactant-like peptide R3L12 exhibits remarkable and unique pH-dependent self-assembly.
• The observed morphological and conformational transitions are driven by pH-induced changes in peptide structure and interactions.
• This peptide's controllable self-assembly into distinct nanostructures holds promise for diverse applications in materials science and nanotechnology.