An automated and efficient conformational search of glycine and a glycine-water heterodimer both in vacuum and in aqueous solution

Stable conformers and the conformational isomerization pathways of glycine and the glycine-H₂O heterodimer were explored using an efficient automated conformational searching method. The Gibbs energies of the conformers and transition structures of glycine and a glycine-H₂O heterodimer at 400, 298, and 150 K were also calculated. In addition, estimated ratios of conformers, assuming thermodynamic equilibrium, were calculated and compared with the results of spectroscopic experiments. Solvent effects were introduced into the exploration process using the polarizable continuum model (PCM), and conversion (tautomerization) pathways from neutral to zwitterionic states for both glycine and a glycine-H₂O heterodimer in aqueous solution were compared.