We present calculations for proline-(H2O)(n) (n = 2-4) to assess the effects of microsolvating water molecules on the relative stability of the zwitterionic vs. canonical forms. We calculate the structures, energies and Gibbs free energies of the conformers at wB97XD/6-311++G(d,p) and MP2/aug-cc-pvdz levels of theory. We find that four water molecules are enough to stabilize the zwitterionic form of proline. By calculating the barriers of the canonical <-> zwitterionic pathways, we suggest that both canonical and zwitterionic forms of proline-(H2O)(4) may be observed in low temperature gas phase. (C) 2014 Elsevier B.V. All rights reserved.