Research ArticleCHEMICAL PHYSICS

Origin of the blueshift of water molecules at interfaces of hydrophilic cyclic compounds

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Science Advances  22 Dec 2017:
Vol. 3, no. 12, e1701400
DOI: 10.1126/sciadv.1701400
  • Fig. 1 Spectra of water molecules in the d-glucose solution.

    (A) Experimental Raman spectrum of the bulk (black line) and SC spectrum (red line). The SC spectrum was obtained using the spectra of d-glucose solutions in 0, 0.05, 0.1, 0.3, and 0.5 M. (B and C) The OH vibrational spectra of water molecules obtained by the Car-Parrinello MD (CPMD) simulations using the wavelet analysis within 3.5 Å of α-d-glucose (red line) (B) and near (red line) and far (blue line) OH bonds (C). The “near” and “far” represent the OH bonds from the monosaccharide oxygen atoms. a.u., arbitrary unit.

  • Fig. 2 Relationship between water arrangement and vibration in the α-d-glucose solution.

    (A) Average TOPs as a function of the distance between the oxygen atoms of monosaccharide and water molecules. Red and blue lines show the calculation without and with monosaccharide oxygen atoms, respectively. (B) RDF as a function of the distance between the oxygen atoms of monosaccharide and water molecules. (C and D) Near and far OH vibrational spectra of water molecules separated by the characteristic regions in the TOP between water and sugar oxygen atoms. Colored lines are the spectra using water molecules located between 2.4 and 2.8 Å (red), 2.8 and 3.3 Å (blue), and 3.3 and 4.0 Å (green).

  • Fig. 3 Density of water molecule oxygen atoms around all the monosaccharides.

    Blue-colored regions represent the first hydration shells, and red-colored regions represent the location of weak H-bonded water molecules, which are defined as water molecules located in the middleTOP region with low values for TOP between water and sugar oxygen atoms.

  • Fig. 4 Formation process of the observed weak H-bonded water molecules around the monosaccharide.

    (A) Average number of H-bonds between water molecules and RDF as a function of the distance between the oxygen atoms of monosaccharide and water molecules. These results were obtained by the classical MD simulations of the α-d-glucose solution at 298 K and 0.1 M using the Transferable Intermolecular Potential with 3 Points (TIP3P) water model. Blue, red, and black represent the number of donor, acceptor, and total H-bonds, respectively. (B) Schematic view of the formation process of the weak H-bonded water molecules. Red region shows 2.4 to 2.8 Å, where water molecules mainly form acceptor H-bonds with the monosaccharide. These water molecules are compatible with the structure of both the monosaccharide and the bulk. Blue region shows 2.8 to 3.3 Å, where water molecules mainly act as a donor with the monosaccharide. In these regions, H-bonds with outer water molecules are unstable.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/12/e1701400/DC1

    fig. S1. Raman spectra of d-glucose solutions at concentrations between 0 and 0.5 M.

    fig. S2. OH vibrational spectra for all water molecules in the system obtained by CPMD simulations.

    fig. S3. OH vibrational spectra of water molecules within 3.5 Å of all isomers.

    fig. S4. Average number of H-bonds between water molecules and RDF as a function of the distance between the oxygen atoms of monosaccharide and water molecules.

    fig. S5. Spectra and water arrangement of water molecules in the NaBr solution.

    fig. S6. I-shaped channel used for Raman experiments.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Raman spectra of D-glucose solutions at concentrations between 0 and 0.5 M.
    • fig. S2. OH vibrational spectra for all water molecules in the system obtained by CPMD simulations.
    • fig. S3. OH vibrational spectra of water molecules within 3.5 Å of all isomers.
    • fig. S4. Average number of H-bonds between water molecules and RDF as a function of the distance between the oxygen atoms of monosaccharide and water molecules.
    • fig. S5. Spectra and water arrangement of water molecules in the NaBr solution.
    • fig. S6. I-shaped channel used for Raman experiments.

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