Structures and energetics of Gly–(H2O)5: Thermodynamic and kinetic stabilities

Calculations are presented for glycine–(H2O)5 clusters, with glycine in canonical or zwitterionic form. The energies of zwitterionic conformers are calculated to be higher than the canonical ones by 2–4 kcal/mol. The dynamic pathways of canonical ←→ zwitterion isomerization are presented, along with the magnitude of the activation barriers. We find that some of the zwitterionic glycine–(H2O)5 clusters are kinetically stable for experimental observation due to considerable barriers (∼9 kcal/mol).