From Amorphous Bundles to Nanoporous Peptide Frameworks: Solvent-Driven Self-Assembly of Pro-Val-Pro-Val

Area of Science:

• Biomolecular self-assembly
• Peptide nanostructures
• Supramolecular chemistry

Background:

• Peptides are versatile biomolecules known for forming complex noncovalent nanostructures.
• Understanding peptide self-assembly is crucial for designing novel materials and understanding biological processes.

Purpose of the Study:

• To investigate the solvent-directed self-assembly of the amphiphilic tetrapeptide l-prolyl-l-valyl-l-prolyl-l-valine (PVPV).
• To characterize the resulting molecular frameworks using various analytical techniques.
• To evaluate the accuracy of computational modeling in predicting these self-assembly behaviors.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• X-ray diffraction
• Computational modeling (density functional theory)
• NMR crystallography on isotopically labeled samples

Main Results:

• PVPV self-assembles into two distinct helical frameworks driven by charge-assisted hydrogen bonding.
• Water-methanol crystallization yields a porous tetragonal framework.
• Pure water leads to either a low-hydration amorphous phase or a dense triclinic form.
• Computational models struggle to predict the energetically less favorable porous structure, highlighting the role of water disorder and flexibility.
• Advanced NMR revealed subtle molecular distortions in the low-hydration phase.

Conclusions:

• Solvent environment critically dictates peptide nanostructure formation.
• Peptide self-assembly can lead to metastable structures not predicted by standard computational methods.
• Advanced NMR techniques are essential for characterizing complex disordered peptide phases.