Mechanism of Zn²⁺ Electroreduction Acceleration by γ-Aminobutyric Acid: A Combined Electrochemical and Molecular Dynamics Study

The catalytic influence of γ-aminobutyric acid (GABA) on Zn²⁺ electroreduction at a mercury electrode was investigated in an acetate buffer. Electrochemical measurements, including DC polarography and differential capacity, indicate that GABA facilitates charge transfer through the formation of “cap-pair” surface bridges. This acceleration is reflected in a systematic increase in the standard rate constant and the transfer coefficient. Molecular dynamics simulations complement these findings by characterizing the conformational properties of GABA, showing a transition toward more folded forms in concentrated environments. Moreover, MD simulations demonstrate that GABA reduces the Zn²⁺ solvation number, providing a structural pathway that lowers the dehydration barrier prior to charge transfer. These observations correlate with the measured decrease in diffusion coefficients as the neurotransmitter concentration increases. The results establish a direct link between the zwitterionic adsorption of GABA and the reduction in the energetic barrier in the zinc electroreduction process.