The microhydration of the complexes formed by trivalent metal ions (Al3+, Ga3+, In3+) and zwitterionic glycine biomolecule has been investigated systematically by first-principles calculations. A first solvation shell with a hexacoordinate configuration is found to occur at the metal center due to the delicate equilibrium between the steric hindrance and the charge transfer from the ligands to the metal. The hydrogen bond forms between the water ligand and glycine bioligand in the first solvation shell, providing an energetically favorable pathway for the proton transfer from the inner shell to the outer shell. (C) 2012 Elsevier B.V. All rights reserved.