Short-range interactions of concentrated proline in aqueous solution

Area of Science:

• Biochemistry
• Physical Chemistry
• Solution Chemistry

Background:

• Proline is an amino acid known for its role as a hydrotrope.
• Understanding molecular interactions in concentrated solutions is crucial for biological function.

Purpose of the Study:

• To investigate the molecular interactions of proline in highly concentrated aqueous solutions.
• To elucidate the structural organization of proline at high concentrations.

Main Methods:

• Utilized a combination of experimental and computational techniques.
• Performed three-dimensional structural analysis.

Main Results:

• Identified the presence of proline-proline dimers instead of aggregates or crystallites.
• Observed cyclic electrostatic interactions between carboxylate (CO2-) and ammonium (NH2+) groups forming the dimers.
• Found that water molecules aggregate around these dimers, potentially bridging them.

Conclusions:

• The observed proline dimerization, driven by electrostatic interactions, provides a structural basis for its hydrotrope activity.
• This dimerization may create hydrophobic pockets facilitating interactions with other molecules.
• Highlights the importance of 3D structural analysis for understanding concentrated solutions.