Conformation of the neurotransmitter γ-aminobutyric acid in liquid water

We study the conformation and reorientation dynamics of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) under neutral and acidic conditions using a combination of broadband dielectric relaxation spectroscopy and polarization-resolved femtosecond mid-infrared pump–probe spectroscopy. We find that both zwitterionic and cationic GABA adopt nearly linear conformations in aqueous solution, meaning that the two charged functional groups of the GABA zwitterion are hydrated separately.