Thermodynamic Investigation of Tripeptide Tyr-Aaa-Gly in Gas Phase in Different Solvents

Tripeptide Tyr-Aaa-Gly (1a, 2b) is methionine-enkephalin analogues [Aaa = (R,S)-(1adamantyl)glycine]. The unique structure of adamantane is reflected in its highly unusual physical and chemical properties, which can have many applications including drug design and drug delivery. In this research, Quantum-mechanical calculations were performed at the HF/6-31G, HF/6-31G*, B3LYP/6-31G, B3LYP/6-31+G, B3LYP/6-31G* and BLYP/6-31G** levels in the gas phase and four solvents such as water, DMSO, methanol and dichloromethane. According to these theoretical results we extracted thermo chemical parameters such as energy of the whole system, enthalpy, Gibbs free energy and entropy for Tripeptide Tyr-Aaa-Gly. The results were revealed that parameters are strongly affected by inducing different solvent media. According to these theoretical results it can be drastically concluded that the dielectric permittivity of the solvent is a key factor that determines the chemical behavior of Tripeptide Tyr-Aaa-Gly in solution.