Structural Properties of Phenylalanine-Based Dimers Revealed Using IR Action Spectroscopy

Area of Science:

• Biochemistry
• Chemical Physics
• Materials Science

Background:

• Phenylalanine-containing peptides are implicated in neurodegenerative diseases.
• The self-assembly of phenylalanine peptides can yield functional nanostructures with technological and medical applications.
• Understanding the stability of these nanostructures requires investigating the early stages of peptide self-assembly.

Purpose of the Study:

• To investigate the initial self-assembly stages of phenylalanine-derived peptides in the gas phase.
• To identify the critical intra- and intermolecular interactions driving dimer formation.
• To characterize the structural diversity of peptide dimers using IR action spectroscopy.

Main Methods:

• Gas-phase IR action spectroscopy was employed to study peptide dimers.
• Far-IR spectroscopy was utilized to differentiate structural families.
• Computational analysis was used to assign specific structures and interactions.

Main Results:

• The 2-(2-amino-2-phenylacetamido)-2-phenylacetic acid (PhgPhg) dimer adopts a highly symmetric structure with two intermolecular hydrogen bonds and aromatic rings folded away from the backbone.
• Comparison with cyclic L-phenylalanyl-L-phenylalanine (cyclo-FF) suggests the linear FF dimer has a less ordered structure.
• The addition of a third phenylalanine residue (FFF) leads to a more organized dimer structure stabilized by multiple intermolecular hydrogen bonds.

Conclusions:

• The study elucidates the structural preferences and intermolecular interactions governing the self-assembly of phenylalanine-based peptide dimers.
• Specific structural motifs, such as hydrogen bonding and aromatic ring orientation, are critical for dimer stability.
• These findings contribute to the understanding of peptide self-assembly for designing functional nanomaterials.