Density Functional Theory (DFT) and Thermodynamics Calculations of Amino Acids with Polar Uncharged Side Chains

The goal of the present work was to evaluate the chemical reactivity of amino acids with polar uncharged side chains (serine, threonine, asparagine and glutamine) using density functional theory (DFT) and thermodynamics modeling by calculating a series of molecular descriptors and properties of their optimized geometries. The predictive calculations were achieved with Spartan software from Wavefunction, Inc. Irvine, CA, USA, hybrid algorithm B3LYP (Becke’s three-term functional; Lee, Yang, Parr exchange hybrid) and polarization basis set 6-31G(d,p) for equilibrium geometry at ground state in vacuum and in water, after energy minimization and geometry optimization. Thermodynamic properties (zero-point energy, enthalpy, constant volume heat capacity, entropy and Gibbs energy) for these derivatives were calculated and related to electrochemical ligand behavior. Reduction and oxidation potentials were correlated to their calculated energy levels for molecular orbitals.