Tube to ribbon transition in a self-assembling model peptide system

Area of Science:

• Supramolecular chemistry
• Biophysics
• Materials science

Background:

• Peptides self-assemble into various supramolecular structures (tubes, ribbons, sheets) driven by β-sheet formation.
• Understanding the thermodynamic forces governing these self-assembly processes is crucial for controlling structure and function.
• The A_nK peptide system exhibits a length-dependent structural transition from tubes to ribbons.

Purpose of the Study:

• To analyze the thermodynamic driving forces behind the structural transition in the A_nK peptide system.
• To develop a simple thermodynamic model explaining the observed tube-to-ribbon transition.
• To elucidate the role of specific energy contributions in peptide self-assembly.

Main Methods:

• Development of a simple thermodynamic model for self-assembling peptides.
• Inclusion of interfacial tension, β-sheet twist angle penalty, and hydrogen bond deformation energy.
• Analysis of energy contributions as a function of peptide length (n).

Main Results:

• The thermodynamic model incorporates interfacial tension, twist penalty, and hydrogen bond deformation.
• Hydrogen bond deformation energy varies significantly with the self-assembled structure.
• The model predicts tube structures are favored for shorter A_nK peptides, with a crossover to ribbons around n≈13.

Conclusions:

• The developed thermodynamic model successfully captures the qualitative behavior of the A_nK peptide self-assembly.
• Hydrogen bond deformation is identified as a key factor influencing the structural transition.
• The study provides insights into the thermodynamic principles governing peptide self-assembly into different supramolecular architectures.