Conformers of Zwitterionic Glycine in Aqueous Phase

Zwitterionic glycine was investigated for its major conformers and their isomerizations in aqueous phase by QM/MM-MD. The rotameric barrier of zwitterionic glycine along C−C bond is approximately 2 kcal/mol higher than that of non-ionized one. It can be attributed to the strong electrostatic effects of zwitterion, which attracts water solvents more tightly. Unlike the previous quantum mechanical calculations, our QM/MM-MD found that only the gauche conformer as stable minima along the C−N bond rotation. Overall, the preferred conformers in real solution are different from those found with limited clusters, necessitating the use of QM/MM-MD.