Divalent metal cation speciation and binding to surface-bound oligonucleotide single strands studied by second harmonic generation

Joseph G. Holland, David S. Jordan, Franz M. Geiger

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The binding of Sr(II), Ca(II), Mg(II), Ba(II), Mn(II), Zn(II), and Cd(II) to silica/water interfaces functionalized with A15T6 oligonucleotides was quantified at pH 7 and 10 mM NaCl using the Eisenthal π(3) technique. The binding free energies range from -31.1(6) kJ/mol for Ba(II) to -33.8(4) kJ/mol for Ca(II). The ion densities were found to range from 2(1) ions/strand for Zn(II) to 11(1) ions/strand for Cd(II). Additionally, we quantified Mg(II) binding in the presence of varying background electrolyte concentrations which showed that the binding free energies changed in a linear fashion from -39.3(8) to -27(1) kJ/mol over the electrolyte concentration range of 1-80 mM, respectively. An adsorption free energy versus interfacial potential analysis allowed us to elucidate the speciation of the bound Mg(II) ions and to identify three possible binding pathways. Our findings suggest that Mg(II) binds as a fully hydrated divalent cation, most likely displacing DNA-bound Na ions. These measurements will serve as a benchmark for computer simulations of divalent metal cation/DNA interactions for geochemical and biosensing applications.

Original languageEnglish (US)
Pages (from-to)8338-8345
Number of pages8
JournalJournal of Physical Chemistry B
Volume115
Issue number25
DOIs
StatePublished - Jun 30 2011

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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