Molecular dynamics simulations of the rehydration of folded and unfolded cytochrome c ions in the vapor phase

Molecular dynamics (MD) simulations have been performed to study the rehydr ation of compact and unfolded cytochrome c ions in the vapor phase. Experim ental studies have shown that the compact conformations adsorb many more wa ter molecules than unfolded ones when exposed to water vapor. MD simulation s performed with up to 150 water molecules reproduce the key experimental o bservations, including a partial refolding caused by hydration. According t o the calculations it is more energetically favorable to hydrate the compac t conformation in the initial stages of hydration, because it is easier for a water molecule to interact simultaneously with several polar groups (due to their proximity). The protonated side chains are not favored hydration sites in the simulations because they have "self-solvation" shells which mu st be disrupted for the water to penetrate. For both conformations, the ads orbed water molecules are mainly located in surface crevices.