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Glycine in aqueous solution: solvation shells, interfacial water, and vibrational spectroscopy from ab initio molecular dynamics
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10.1063/1.3481576
/content/aip/journal/jcp/133/11/10.1063/1.3481576
http://aip.metastore.ingenta.com/content/aip/journal/jcp/133/11/10.1063/1.3481576

Figures

Image of FIG. 1.
FIG. 1.

Representative snapshot of the Gly(aq) system as used in the present AIMD simulations. Water molecules are depicted by a stick representation, glycine by a ball-and-stick model, and the Wannier function centers are shown by small green spheres (colors refer to online version).

Image of FIG. 2.
FIG. 2.

Radial distribution functions for zwitterionic glycine in water of (a) nitrogen site (n), (b) hydrogen sites in ammonium group (c) oxygen sites in carboxylate group , (d) carbon site in carboxylate group , (e) -carbon , and (f) hydrogen sites at -carbon with respect to the oxygen and hydrogen sites of the water molecules using red and blue solid lines, respectively. The corresponding dashed lines represent the running coordination numbers where the scale is provided on the right axes. The preferred staggered planar zwitterionic Gly structure including the site labeling is shown at the bottom (colors refer to online version).

Image of FIG. 3.
FIG. 3.

(a) Dihedral distribution functions of the group in zwitterionic Gly in water, ZW-Gly (black) where , and of the group in neutral Gly in vacuum, Neu-Gly (red) where (M is the middle point of the H atoms in group); the corresponding maximum free energy barriers, , are about 1 and 3 kcal/mol, respectively, at . (b) Dihedral distribution function of the group in zwitterionic Gly (black) where and O is either or , and the group in neutral Gly (red) where and is the bare oxygen; the corresponding maximum free energy barriers are about 3 and 2 kcal/mol, respectively, at . (c) Distribution functions of the closest distance (blue, left/lower axes scales) and the corresponding angle (green, right/upper axes scales) in zwitterionic Gly in water (colors refer to online version).

Image of FIG. 4.
FIG. 4.

Radial distribution functions for zwitterionic glycine in water of (a) each site separately to (using red, green, black lines), (b) each site separately to (red and black lines), (c) each carboxylate oxygen site, (the one closest to the ammonium group, solid red), and (solid black), separately to . The corresponding dashed lines represent in all cases the running coordination numbers with the scale provided on the right axes (colors refer to online version).

Image of FIG. 5.
FIG. 5.

Distribution functions of molecular dipole moments for (a) glycine and (b) water molecules. In (a) neutral Gly in vacuum (blue), isolated zwitterionic Gly vertically transferred from solution into vacuum (dashed red), see text, and zwitterionic Gly solute itself in the solution (black) are shown. In (b) water molecules in the solvation shells of the ammonium group (blue), carboxylate group (red), -carbon (green), and all remaining “outer” water molecules (magenta) are shown in addition to pure bulk water (black) (colors refer to online version).

Image of FIG. 6.
FIG. 6.

Infrared spectra (a, b) and VDOS (c, d) of the zwitterionic Gly solute itself in the solution (red), neutral Gly in vacuum (green), isolated zwitterionic Gly vertically transferred from solution into vacuum (blue), total glycine aqueous solution (black), all water molecules in the solution (cyan), and of pure bulk water (violet). The IR intensity of zwitterionic Gly (red) in (b) is scaled by a factor of ten to enhance its visibility and the VDOS spectra are normalized to unity.

Tables

Generic image for table
Table I.

Comparison of the calculated IR and VDOS spectra with experimental IR spectra for neutral Gly (frequencies in ); ± approximately indicates the broadness of the peaks as given by half of the full width at half maximum.

Generic image for table
Table II.

Comparison of the calculated IR and VDOS spectra with experimental IR and Raman spectra for zwitterionic Gly (frequencies in ); ± approximately indicates the broadness of the peaks as given by half of the full width at half maximum.

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/content/aip/journal/jcp/133/11/10.1063/1.3481576
2010-09-20
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Glycine in aqueous solution: solvation shells, interfacial water, and vibrational spectroscopy from ab initio molecular dynamics
http://aip.metastore.ingenta.com/content/aip/journal/jcp/133/11/10.1063/1.3481576
10.1063/1.3481576
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