A classical molecular dynamics method was used to study the modifications of the solution structure and the properties of glycine zwitterion in aqueous solution due to the increase of glycine zwitterion concentration and the incorporation of Na(+) and Cl(-) ions to the solution. The glycine zwitterion had fundamentally a hydrophilic behavior at infinite dilution, establishing around six hydrogen bonds with the water molecules that surrounded it, which formed a strong hydration layer. Because of the increase of glycine zwitterion concentration, the hydration structure became more compact and the quantity of water molecules bound to this molecule decreased. The Na(+) ion bound to the CO(2) group of glycine, while the Cl(-) ion bound mainly to the NH(3) group of this molecule. The integration of the ions to the hydration layer of the glycine zwitterion produced modifications in the orientational correlation between atoms of glycine zwitterion and water that surrounded them and an increase of the approaches between the glycine zwitterion molecules. The incorporation of ions to the solution also produced changes in the water-water orientational correlation. Decreases of the water-water hydrogen bonds and diffusion coefficient of all molecules were observed when the glycine zwitterion concentration increased and when the ions were incorporated to the solution.

Articles you may be interested in Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), Universidad Nacional de la Plata (UNLP)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC), B1900BTE, LaWe have studied the hydration and diffusion of the hydroxyl radical OH 0 in water using classical molecular dynamics. We report the atomic radial distribution functions, hydrogen-bond distributions, angular distribution functions, and lifetimes of the hydration structures. The most frequent hydration structure in the OH 0 has one water molecule bound to the OH 0 oxygen ͑57% of the time͒, and one water molecule bound to the OH 0 hydrogen ͑88% of the time͒. In the hydrogen bonds between the OH 0 and the water that surrounds it the OH 0 acts mainly as proton donor. These hydrogen bonds take place in a low percentage, indicating little adaptability of the molecule to the structure of the solvent. All hydration structures of the OH 0 have shorter lifetimes than those corresponding to the hydration structures of the water molecule. The value of the diffusion coefficient of the OH 0 obtained from the simulation was 7.1ϫ 10 −9 m 2 s −1 , which is higher than those of the water and the OH − .

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