Solvent-Encoded Intrinsic Emission and Self-Assembly of Coiled-Coil-Based Foldamers

Area of Science:

• Biomaterials Science
• Supramolecular Chemistry
• Photophysics

Background:

• Coiled-coil peptides are versatile scaffolds for engineering foldamers.
• Cyclic β-amino acids, like trans-(1S,2S)-2-aminocyclopentanecarboxylic acid (trans-ACPC), can be incorporated to tailor foldamer properties.
• Understanding how solvent influences foldamer autofluorescence and self-assembly is crucial for designing novel nanomaterials.

Purpose of the Study:

• To investigate the impact of solvent polarity and hydrogen-bonding capacity on the autofluorescence and supramolecular organization of trans-ACPC-modified coiled-coil peptides.
• To establish a structure-solvent-photophysics relationship for these engineered foldamers.

Main Methods:

• Synthesis and characterization of trans-ACPC-modified and unmodified coiled-coil peptides.
• Spectroscopic techniques including circular dichroism (CD), steady-state and time-resolved fluorescence spectroscopy (SSFS and TRFS).
• Microscopy (transmission electron microscopy, TEM) and vibrational spectroscopy (ATR-FTIR) were employed in various solvents (water, ethanol, acetonitrile).

Main Results:

• All peptides exhibited intrinsic, label-free fluorescence with emission properties dependent on solvent and aggregate morphology.
• Incorporation of trans-ACPC reduced solvent sensitivity and promoted more consistent photophysical responses.
• Solvent dictated aggregate morphology: water favored fibrils, ethanol yielded globular/twisted aggregates, and acetonitrile produced compact clusters.
• ATR-FTIR confirmed solvent-dependent hydrogen-bond networks and backbone interactions influencing emission.

Conclusions:

• Solvent environment directly programs the intrinsic emissive states of these foldamers by altering backbone packing and hydrogen-bond topology.
• trans-ACPC-containing coiled-coils demonstrate potential as intrinsically emissive nanomaterials and optical probes without external labeling.
• These findings provide a framework for designing functional nanomaterials with tunable photophysical properties.