Does arginine aggregate formation in aqueous solutions follow a two-step mechanism?

Area of Science:

• Biophysical Chemistry
• Materials Science
• Structural Biology

Background:

• Amino acid aggregation is crucial in biological systems and material science.
• Understanding the driving forces and mechanisms of amino acid self-assembly is essential.

Purpose of the Study:

• To investigate the formation of aggregates in arginine aqueous solutions.
• To elucidate the driving forces, mechanisms, and structural properties of these aggregates.
• To explore the implications for amino acid-specific aggregation and protein homochirality.

Main Methods:

• Light scattering techniques to study aggregate formation.
• Density functional theory (DFT) calculations to verify hydrogen bonding.
• Cryo-electron microscopy (Cryo-EM) for morphology analysis.
• Energy loss measurements to determine aggregate state.
• pH and solute concentration studies on various amino acid solutions.

Main Results:

• Hydrogen bonding identified as the primary driving force for arginine (Arg) aggregate formation.
• Aggregates were determined to be in a solid state, with a liquid intermediate stage observed during a two-step aggregation process.
• Aggregation is amino acid-specific, influenced by pH, concentration, and water structure.
• Homochirality was observed in the resulting aggregates.

Conclusions:

• Arginine aggregation in aqueous solutions is driven by hydrogen bonding and results in solid-state structures.
• The study provides insights into amino acid-specific aggregation mechanisms and the origin of protein homochirality.
• Water structure around amino acids plays a role in predicting aggregate formation.