Ion-specific induced fluctuations and free energetics of aqueous protein hydrophobic interfaces: Toward connecting to specific-ion behaviors at aqueous liquid-vapor interfaces

Di Cui, Shuching Ou, Eric Peters, Sandeep Patel

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

We explore anion-induced interface fluctuations near protein-water interfaces using coarse-grained representations of interfaces as proposed by Willard and Chandler (J. Phys. Chem. B 2010, 114, 1954-1958). We use umbrella sampling molecular dynamics to compute potentials of mean force along a reaction coordinate bridging the state where the anion is fully solvated and one where it is biased via harmonic restraints to remain at the protein-water interface. Specifically, we focus on fluctuations of an interface between water and a hydrophobic region of hydrophobin-II (HFBII), a 71 amino acid residue protein expressed by filamentous fungi and known for its ability to form hydrophobically mediated self-assemblies at interfaces such as a water/air interface. We consider the anions chloride and iodide that have been shown previously by simulations as displaying specific-ion behaviors at aqueous liquid-vapor interfaces. We find that as in the case of a pure liquid-vapor interface, at the hydrophobic protein-water interface, the larger, less charge-dense iodide anion displays a marginal interfacial stability compared with that of the smaller, more charge-dense chloride anion. Furthermore, consistent with the results at aqueous liquid-vapor interfaces, we find that iodide induces larger fluctuations of the protein-water interface than chloride.

Original languageEnglish (US)
Pages (from-to)4490-4504
Number of pages15
JournalJournal of Physical Chemistry B
Volume118
Issue number17
DOIs
StatePublished - May 1 2014

ASJC Scopus subject areas

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

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