Self-assembling behaviour of a modified aromatic amino acid in competitive medium

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Chemical Biology

Background:

• Phenylalanine (Phe) is a key aromatic amino acid in peptide synthesis, known for its self-assembly driven by aromatic interactions.
• Modifying amino acids can tune their self-assembly behavior for novel material properties.

Purpose of the Study:

• To investigate the impact of introducing a nitro group onto phenylalanine to create electron-deficient 4-nitrophenylalanine (4NP).
• To explore how 4NP's self-assembly differs from native Phe in various solvents and solvent mixtures.
• To characterize the resulting self-assembled structures and understand the underlying interactions.

Main Methods:

• Synthesis and characterization of 4-nitrophenylalanine (4NP).
• Gelation studies in DMSO and crystallization studies in water.
• Structural analysis using X-ray diffraction, UV-Vis spectroscopy, and FE-SEM.
• Computational modeling using density functional theory (DFT) to simulate 4NP structure in DMSO.

Main Results:

• 4-nitrophenylalanine (4NP) exhibits significantly enhanced gelation efficiency in DMSO compared to phenylalanine.
• 4NP forms hydrogen-bonding mediated crystals in water, distinct from its DMSO assembly.
• Solvent properties (DMSO, water, and mixtures) profoundly influence 4NP's self-assembly patterns.
• DFT simulations revealed a different theoretical structure of 4NP in DMSO compared to its crystalline form in water.

Conclusions:

• Electron-deficient 4-nitrophenylalanine (4NP) is a highly effective gelator and self-assembling molecule.
• The choice of solvent and its properties critically dictate the self-assembly outcome of 4NP.
• This study demonstrates a strategy for tuning amino acid self-assembly through chemical modification for materials design.