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 (similar to 9 kcal/mol). (C) 2007 Elsevier B.V. All rights reserved.