A computational study of TyrGly hydration

Twenty-two conformers of the neutral tyrosine-glycine (TyrGly) dipeptide have been studied at the mPW2PLYP-D2/def2-TZVP level in the gas phase, in implicit solvent and with one explicit water molecule. Implicit solvation brings the conformers closer in energy, whereas explicit monosolvation significantly extends the range of stability of the complexes. Thus, interaction with a single water molecule preferentially stabilises some conformers over others. The most stable conformer in the gas phase remains the most stable in implicit solvation and explicit monosolvation, though the third most stable conformer in the gas phase is nearly iso-energetic in implicit solvation. The two most stable monohydrated complexes are based on the folded most stable conformer in the gas phase and only differ slightly in the orientation of the water molecule. The water molecule increases the foldedness of these structures by bridging the carboxylic acid group and phenyl OH.