Chirality of Alanine Molecules in Water Solvent: A Theoretical Perspective

Sequential quantum mechanics/molecular mechanics (QM/MM) calculations combining the average solvent electrostatic configuration (ASEC) and the free energy gradient method are employed to locate minimum structures of α- and β-alanine in a water environment. Herein, we study the solvation effects in the nuclear magnetic resonance (NMR) spectroscopy, vibrational circular dichroism (VCD) spectroscopy, and electronic circular dichroism (ECD) spectroscopy of dl-α-alanine and β-alanine molecules. Our results point out that the ASEC-FEG (average solvent electrostatic configuration with the free energy gradient) method is a suitable approach for finding equilibrium structures of the alanine molecules in aqueous solution. Its accuracy is checked by comparing the optimized structures with those reached by the polarizable continuum model (PCM) and via experimental data. NMR parameters and vibrational and electronic UV-vis spectra are computed with a remarkable agreement with their corresponding experimental values.