Anion-Anion Complexes Established between Aspartate Dimers.

Area of Science:

• Computational chemistry
• Molecular modeling
• Biophysics

Background:

• Aspartate-aspartate dimers are relevant in biological systems.
• Understanding dimer formation requires studying interactions in different phases.
• Theoretical simulations are crucial for detailed molecular analysis.

Purpose of the Study:

• To investigate the stability and formation of aspartate-aspartate dimers in aqueous and gas phases.
• To analyze the nature of hydrogen bonds and interactions within these dimers.
• To determine the energy barriers for dimer formation in different environments.

Main Methods:

• Theoretical simulations using the polarizable continuum model (PCM) for hydration effects.
• Quantum theory of atoms in molecules (QTAIM) and interacting quantum atoms (IQA) for interaction analysis.
• Calculation of energy barriers for dimer formation.

Main Results:

• Spontaneous formation of aspartate-aspartate dimers observed in aqueous phase.
• Significant energy barriers (100.8–263.2 kJ/mol) for dimer formation in the gas phase.
• Aqueous phase hydrogen bonds (N-H⋅⋅⋅O) are predominantly electrostatic with increasing covalent character.
• Observed H⋅⋅⋅H interactions are stabilizing and quantum in nature.

Conclusions:

• Hydration significantly facilitates aspartate-aspartate dimer formation.
• The nature of hydrogen bonding in aqueous solution is primarily electrostatic.
• Intermolecular distances and interaction types dictate molecular recognition in dimer formation.