Zwitterionization of glycine in water environment: Stabilization mechanism and NMR spectral signatures

Author(s)

Valverde, Danillo ^{[1, 2]} ; da Costa Ludwig, Zelia Maria ^[3] ; da Costa, Celia Regina ^[4] ; Ludwig, Valdemir ^[3] ; Georg, Herbert C. ^[2]

Affiliation

^[1] Univ Sao Paulo, Inst Fis, Cidade Univ, BR-05508090 Sao Paulo, SP - Brazil

^[2] Univ Fed Goias, Inst Fis, CP 131, BR-74001970 Goiania, Go - Brazil

^[3] Univ Fed Juiz de Fora, Dept Fis, BR-36036330 Juiz De Fora, MG - Brazil

^[4] Politecn Milan, Dipartimento Design, Milan - Italy

• Document type: Journal article
• Source: Journal of Chemical Physics; v. 148, n. 2 JAN 14 2018.
• Web of Science Citations: 2

Abstract

At physiological conditions, myriads of biomolecules (e.g., amino acids, peptides, and proteins) exist predominantly in the zwitterionic structural form and their biological functions will result in these conditions. However these geometrical structures are inaccessible energetically in the gas phase, and at this point, stabilization of amino-acids in physiological conditions is still under debate. In this paper, the electronic properties of a glycine molecule in the liquid environment were studied by performing a relaxation of the glycine geometry in liquid water using the free energy gradient method combined with a sequential quantum mechanics/molecular mechanics approach. A series of Monte Carlo Metropolis simulations of the glycine molecule embedded in liquid water, followed by only a quantum mechanical calculation in each of them were carried out. Both the local and global liquid environments were emphasized to obtain nuclear magnetic resonance (NMR) parameters for the glycine molecule in liquid water. The results of the equilibrium structure in solution and the systematic study of the hydrogen bonds were used to discard the direct proton transfer from the carboxyl group to the ammonium group of the glycine molecule in water solution. The calculations of the Density Functional Theory (DFT) were performed to study the polarization of the solvent in the parameters of nuclear magnetic resonance of the glycine molecule in liquid water. DFT calculations predicted isotropic chemical changes on the H, C, N, and O atoms of glycine in liquid water solution which agree with the available experimental data. Published by AIP Publishing. (AU)

• FAPESP's process: 17/02612-4 - Dynamics of excited states and spectroscopic properties of natural and synthetic DNA and RNA derivatives in solvent environment
• Grantee: Danillo Pires Valverde
• Support Opportunities: Scholarships in Brazil - Doctorate