DENSITY FUNCTIONAL THEORY (DFT) AND THERMODYNAMICS CALCULATIONS OF AMINO ACIDS WITH POLAR UNCHARGED SIDE CHAINS

Introduction: The goal of the present work was to evaluate the chemical reactivity of amino acids with polar uncharged sidechains (Setine, 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.

Experimental and/or Modelling: The predictive calculations were achieved with Spartan software from Wavefunction, Inc. Irvine CA USA [1], hybrid algorithm B3LYP (the Becke’s 3-term functional; Lee, Yang, Parr exchange Hybrid) [2, 3] and polarization basis set 6-31G (d, p) for equilibrium geometry at ground state in vacuum and in water, after minimization energy and geometry optimization.

Thermodynamic properties (zero-point energy, enthalpy, constant volume heat capacity, entropy and Gibbs energy) for these derivatives have been calculated and related to ligands electrochemical behavior. Reduction and oxidation potentials have been correlated to their calculated energy levels for LUMO and HOMO orbitals.

The results of this work were compared with those obtained for other amino acids, with different functional groups.