Interactions of biopolymers with silica surfaces

Force measurements and electronic structure calculation studies

Kideok D. Kwon, Virginia Vadillo-Rodriguez, Bruce Ernest Logan, James D. Kubicki

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Pull-off forces were measured between a silica colloid attached to an atomic force microscope (AFM) cantilever and three homopolymer surfaces representing constituents of extracellular polymeric substances (EPS). The pull-off forces were -0.84 (±0.16), -0.68 (±0.15), and -2.37 (±0.31) nN as measured in water for dextran, phosphorylated dextran, and poly-l-lysine, respectively. Molecular orbital and density functional theory methods (DFT) were applied to analyze the measured pull-off forces using dimer clusters representing interactions between the three polymers and silica surfaces. Binding energies for each dimer were calculated with basis set superposition error (BSSE) and interpolated using corrections for silica surface hydroxyl density and silica charge density. The binding energies were compared with the normalized pull-off forces with the effective silica surface area contacting the polymer surfaces. The predicted binding energies at a -0.064 C/m2 silica surface charge density corresponding to circum-neutral pH were -0.055, -0.029, and -0.338 × 10-18 J/nm2 for the dimers corresponding to the silica surface with dextran, phosphorylated dextran, and poly-l-lysine, respectively. Polarizable continuum model (PCM) calculations with different solvents, silanol vibrational frequency calculations, and orbital interaction analysis based on natural bonding orbital (NBO) showed that phosphate groups formed stronger H-bonds with neutral silanols than hydroxyl and amino functional groups of polymers, implying that phosphate containing polymers would play important roles in EPS binding to silica surfaces.

Original languageEnglish (US)
Pages (from-to)3803-3819
Number of pages17
JournalGeochimica et Cosmochimica Acta
Volume70
Issue number15
DOIs
StatePublished - Aug 1 2006

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Biopolymers
Force measurement
Surface measurement
Silicon Dioxide
Electronic structure
silica
Dextrans
Polymers
polymer
Binding energy
Dimers
Charge density
Hydroxyl Radical
Lysine
Phosphates
phosphate group
energy
calculation
electronics
Colloids

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

Cite this

Kwon, Kideok D. ; Vadillo-Rodriguez, Virginia ; Logan, Bruce Ernest ; Kubicki, James D. / Interactions of biopolymers with silica surfaces : Force measurements and electronic structure calculation studies. In: Geochimica et Cosmochimica Acta. 2006 ; Vol. 70, No. 15. pp. 3803-3819.
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Interactions of biopolymers with silica surfaces : Force measurements and electronic structure calculation studies. / Kwon, Kideok D.; Vadillo-Rodriguez, Virginia; Logan, Bruce Ernest; Kubicki, James D.

In: Geochimica et Cosmochimica Acta, Vol. 70, No. 15, 01.08.2006, p. 3803-3819.

Research output: Contribution to journalArticle

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T1 - Interactions of biopolymers with silica surfaces

T2 - Force measurements and electronic structure calculation studies

AU - Kwon, Kideok D.

AU - Vadillo-Rodriguez, Virginia

AU - Logan, Bruce Ernest

AU - Kubicki, James D.

PY - 2006/8/1

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AB - Pull-off forces were measured between a silica colloid attached to an atomic force microscope (AFM) cantilever and three homopolymer surfaces representing constituents of extracellular polymeric substances (EPS). The pull-off forces were -0.84 (±0.16), -0.68 (±0.15), and -2.37 (±0.31) nN as measured in water for dextran, phosphorylated dextran, and poly-l-lysine, respectively. Molecular orbital and density functional theory methods (DFT) were applied to analyze the measured pull-off forces using dimer clusters representing interactions between the three polymers and silica surfaces. Binding energies for each dimer were calculated with basis set superposition error (BSSE) and interpolated using corrections for silica surface hydroxyl density and silica charge density. The binding energies were compared with the normalized pull-off forces with the effective silica surface area contacting the polymer surfaces. The predicted binding energies at a -0.064 C/m2 silica surface charge density corresponding to circum-neutral pH were -0.055, -0.029, and -0.338 × 10-18 J/nm2 for the dimers corresponding to the silica surface with dextran, phosphorylated dextran, and poly-l-lysine, respectively. Polarizable continuum model (PCM) calculations with different solvents, silanol vibrational frequency calculations, and orbital interaction analysis based on natural bonding orbital (NBO) showed that phosphate groups formed stronger H-bonds with neutral silanols than hydroxyl and amino functional groups of polymers, implying that phosphate containing polymers would play important roles in EPS binding to silica surfaces.

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