Increasing attention has been drawn to dipeptide nanotubes for their varied potential applications as semi-conductors, bio-compatible scaffolds, drug-delivery agents, and for energy storage while being relatively non-toxic materials. Furthermore, dipeptides are shown to self-assemble into nanotubes with minimal difficulty. Although recent literature has demonstrated the self-assembling trait of dipeptides, a fundamental understanding of the conditions that drive the process is still lacking. In this study, the effect of non-covalent interactions as the driving force for self-assembly of dityrosine was investigated from its monomeric, dimeric, and hexameric structures obtained using density functional based tight binding method. The different interaction energies were quantified from these structures from a pair interaction energy decomposition analysis using the fragment molecular orbital method. Results showed that the majority of the stabilization, as the system size increases, is mainly attributed to hydrogen bonding interactions. Considerable contributions from π-π stacking interactions were also observed between the aromatic rings of the dipeptide monomers. Two and three-layer hexamer stacks also revealed interlayer hydrogen bonding interactions as well as interlayer π-π stacking sites which stabilizes the nanotube structure. Electrostatic effects from solvation also contributed to the favorability of the hexamer formation and revealed the preference of the cyclic dityrosine over the linear dityrosine form, an observation consistent with experimental results. Molecular dynamics simulation of the initial aggregation of solvated dityrosine monomers revealed the backbone-backbone interactions optimal for nanotube growth. As the nanotube increases in size, the number of non-covalent interactions via hydrogen-bonding and π-π stacking increases and can be viewed as both the stabilizing factor as well as the driving force for dipeptide nanotube self-assembly.

Role of non-covalent interactions towards the self-assembly of dityrosine nanotubes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.