Hydration - The Role of the Charge-Carrying Group
Another factor that can influence hydration is the identity of the peptide's charge-carrying group. Gas-phase peptide cations are typically protonated at the N-terminus and/or at basic amino acid residues such as arginine. Temperature-dependent equilibrium studies indicate that arginine-containing peptides have somewhat smaller water binding energies than peptides without arginine.
Experimental water binding energies for compounds with amine and guanidine
charge groups. Dialanine is protonated at the N-terminus (structure
on left) and forms a 14.8 kcal/mol bond with water as does n-declyamine.
In both cases, water binds to the