Microsolvation of glycine: a DFT study

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular modeling

Background:

• Glycine, the simplest amino acid, exists in neutral and zwitterionic forms.
• Understanding solvation is crucial for predicting molecular behavior in biological systems.
• Microsolvation studies provide insights into the initial interactions of solutes with solvent molecules.

Purpose of the Study:

• To investigate the microsolvation of neutral and zwitterionic glycine using computational methods.
• To identify the most stable glycine-water clusters for varying numbers of water molecules.
• To analyze the structural and energetic properties of these clusters.

Main Methods:

• Ab initio quantum chemical calculations using the PBE1PBE/6-311+G(d,p) level of theory.
• Extensive conformational searches to locate low-energy glycine-water clusters.
• Analysis of hydrogen-bonding networks within the clusters.

Main Results:

• Identified lowest energy structures for glycine-water clusters from one to seven water molecules.
• Observed that neutral glycine is the preferred form in clusters with 0-6 water molecules.
• Found that neutral and zwitterionic glycine are energetically equivalent in clusters with 7 water molecules.

Conclusions:

• The microsolvation environment significantly influences the preferred form of glycine.
• Hydrogen bonding plays a critical role in stabilizing glycine-water clusters.
• The transition from neutral to zwitterionic dominance occurs around seven water molecules.