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Karl Mechtler – One of the best experts on this subject based on the ideXlab platform.

  • Anion Exchange chromatography of phosphopeptides weak Anion Exchange versus strong Anion Exchange and Anion Exchange chromatography versus electrostatic repulsion hydrophilic interaction chromatography
    Analytical Chemistry, 2015
    Co-Authors: Andrew J Alpert, Otto Hudecz, Karl Mechtler
    Abstract:

    Most phosphoproteomics experiments rely on prefractionation of tryptic digests before online liquid chrochromatography-mass spectrometry. This study compares the potential and limitations of electrostatic repulsion–hydrophilic interaction chromatography (ERLIC) and AnionExchange chromatography (AEX). At a pH higher than 5, phosphopeptides have two negative charges per residue and are well-retained in AEX. However, peptides with one or two phosphate groups are not separated from peptides with multiple Asp or Glu residues, interfering with the identification of phosphopeptides. At a pH of 2, phosphate residues have just a single negative charge but Asp and Glu are uncharged. This facilitates the separation of phosphopeptides from unmodified acidic peptides. Singly phosphorylated peptides are retained weakly under these conditions, due to electrostatic repulsion, unless hydrophilic interaction is superimposed in the ERLIC mode. Weak AnionExchange (WAX) and strong AnionExchange (SAX) columns were compared, wit…

Andrew J Alpert – One of the best experts on this subject based on the ideXlab platform.

  • Anion Exchange chromatography of phosphopeptides weak Anion Exchange versus strong Anion Exchange and Anion Exchange chromatography versus electrostatic repulsion hydrophilic interaction chromatography
    Analytical Chemistry, 2015
    Co-Authors: Andrew J Alpert, Otto Hudecz, Karl Mechtler
    Abstract:

    Most phosphoproteomics experiments rely on prefractionation of tryptic digests before online liquid chromatography-mass spectrometry. This study compares the potential and limitations of electrostatic repulsion–hydrophilic interaction chromatography (ERLIC) and AnionExchange chromatography (AEX). At a pH higher than 5, phosphopeptides have two negative charges per residue and are well-retained in AEX. However, peptides with one or two phosphate groups are not separated from peptides with multiple Asp or Glu residues, interfering with the identification of phosphopeptides. At a pH of 2, phosphate residues have just a single negative charge but Asp and Glu are uncharged. This facilitates the separation of phosphopeptides from unmodified acidic peptides. Singly phosphorylated peptides are retained weakly under these conditions, due to electrostatic repulsion, unless hydrophilic interaction is superimposed in the ERLIC mode. Weak AnionExchange (WAX) and strong AnionExchange (SAX) columns were compared, wit…

Toshikatsu Sata – One of the best experts on this subject based on the ideXlab platform.

  • studies on Anion Exchange membranes having permselectivity for specific Anions in electrodialysis effect of hydrophilicity of Anion Exchange membranes on permselectivity of Anions
    Journal of Membrane Science, 2000
    Co-Authors: Toshikatsu Sata
    Abstract:

    Abstract Recent studies on Anion Exchange membranes and electrodialysis methods to permeate specific Anions through the membranes are reviewed. The studies are classified: (1) to increase cross-linkage of the Anion Exchange membranes, (2) to form tight surface layers on the Anion Exchange membranes, (3) to decrease hydrophilicity of the Anion Exchange membranes or their surfaces by introducing specific Anion Exchange groups in the membranes, (4) to impregnate hydrophilic compounds in the Anion Exchange membranes to increase hydrophilicity of the membranes, (5) to control permselectivity of Anions by photoirradiation using membranes with a photoresponsive group and (6) to control permselectivity of Anions through thermally responsive Anion Exchange membranes with temperature. Permselectivity of specific Anions through the Anion Exchange membranes is governed mainly by the balance of hydration energy of Anions with hydrophilicity of the membranes, partially by hydrated ionic size of the Anions, except the membranes having an oppositely charged layer on the membrane surface.

  • Studies on Anion Exchange membranes having permselectivity for specific Anions in electrodialysis — effect of hydrophilicity of Anion Exchange membranes on permselectivity of Anions
    Journal of Membrane Science, 2000
    Co-Authors: Toshikatsu Sata
    Abstract:

    Abstract Recent studies on Anion Exchange membranes and electrodialysis methods to permeate specific Anions through the membranes are reviewed. The studies are classified: (1) to increase cross-linkage of the Anion Exchange membranes, (2) to form tight surface layers on the Anion Exchange membranes, (3) to decrease hydrophilicity of the Anion Exchange membranes or their surfaces by introducing specific Anion Exchange groups in the membranes, (4) to impregnate hydrophilic compounds in the Anion Exchange membranes to increase hydrophilicity of the membranes, (5) to control permselectivity of Anions by photoirradiation using membranes with a photoresponsive group and (6) to control permselectivity of Anions through thermally responsive Anion Exchange membranes with temperature. Permselectivity of specific Anions through the Anion Exchange membranes is governed mainly by the balance of hydration energy of Anions with hydrophilicity of the membranes, partially by hydrated ionic size of the Anions, except the membranes having an oppositely charged layer on the membrane surface.

  • Selectivity of Anion Exchange Resin Modified with Anionic Polyelectrolyte.
    Analytical Sciences, 1997
    Co-Authors: Koji Matsusaki, Noriaki Hashimoto, Nobuhiro Kuroki, Toshikatsu Sata
    Abstract:

    In order to change the ion-Exchange selectivity of Anion Exchange resin, especially to make the ion-Exchange of divalent Anions more difficult, the surface of gel-type Anion Exchange resin was modified by the adsorption of an Anionic polyelectrolyte: polycondensation product of sodium naphthalene sulfonate and formaldehyde. After the adsorption of the polymer, ion Exchange capacity decreased and the rate of ion Exchange reaction became slow, though ion Exchange equilibrium constants between two Anions did not change. Especially, the ion Exchange rate of divalent Anions was slower than that of the monovalent Anions. Because an Anionic polyelectrolyte layer was formed on the resin particle, the ion Exchange of Anions with Anion Exchange site was retarded by a sieving effect due to the layer. The divalent Anions became difficult to ion Exchange compared with the monovalent Anions due to the existence of the layer which was charged opposite to the charge of the ion Exchange groups. Using the modified Anion Exchange resin, separation of nitrate ions from sulfate ions was attempted.

R. Stevenson – One of the best experts on this subject based on the ideXlab platform.

  • AnionExchange resins from allylammonium salts
    Journal of Chemical Technology & Biotechnology, 2007
    Co-Authors: A. L. Clingman, J. R. Parrish, R. Stevenson
    Abstract:

    AnionExchange resins of high capacity have been obtained by the polymerisation of allyl-ammonium chlorides. The Exchange rates of different resins have been compared by the measurement of electrical conductivity.

Otto Hudecz – One of the best experts on this subject based on the ideXlab platform.

  • Anion Exchange chromatography of phosphopeptides weak Anion Exchange versus strong Anion Exchange and Anion Exchange chromatography versus electrostatic repulsion hydrophilic interaction chromatography
    Analytical Chemistry, 2015
    Co-Authors: Andrew J Alpert, Otto Hudecz, Karl Mechtler
    Abstract:

    Most phosphoproteomics experiments rely on prefractionation of tryptic digests before online liquid chromatography-mass spectrometry. This study compares the potential and limitations of electrostatic repulsion–hydrophilic interaction chromatography (ERLIC) and AnionExchange chromatography (AEX). At a pH higher than 5, phosphopeptides have two negative charges per residue and are well-retained in AEX. However, peptides with one or two phosphate groups are not separated from peptides with multiple Asp or Glu residues, interfering with the identification of phosphopeptides. At a pH of 2, phosphate residues have just a single negative charge but Asp and Glu are uncharged. This facilitates the separation of phosphopeptides from unmodified acidic peptides. Singly phosphorylated peptides are retained weakly under these conditions, due to electrostatic repulsion, unless hydrophilic interaction is superimposed in the ERLIC mode. Weak AnionExchange (WAX) and strong AnionExchange (SAX) columns were compared, wit…