Liquid-Vapor interfacial properties of aqueous solutions of guanidinium and methyl guanidinium chloride: Influence of molecular orientation on interface fluctuations

Shuching Ou, Di Cui, Sandeep Patel

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The guanidinium cation (C(NH2)3 +) is a highly stable cation in aqueous solution due to its efficient solvation by water molecules and resonance stabilization of the charge. Its salts increase the solubility of nonpolar molecules ("salting-in") and decrease the ordering of water. It is one of the strongest denaturants used in biophysical studies of protein folding. We investigate the behavior of guanidinium and its derivative, methyl guanidinium (an amino acid analogue) at the air-water surface, using atomistic molecular dynamics (MD) simulations and calculation of potentials of mean force. Methyl guanidinium cation is less excluded from the air-water surface than guanidinium cation, but both cations show orientational dependence of surface affinity. Parallel orientations of the guanidinium ring (relative to the Gibbs dividing surface) show pronounced free energy minima in the interfacial region, while ring orientations perpendicular to the GDS exhibit no discernible surface stability. Calculations of surface fluctuations demonstrate that, near the air-water surface, the parallel-oriented cations generate significantly greater interfacial fluctuations compared to other orientations, which induces more long-ranged perturbations and solvent density redistribution. Our results suggest a strong correlation with induced interfacial fluctuations and ion surface stability. These results have implications for interpreting molecular-level, mechanistic action of this osmolyte's interaction with hydrophobic interfaces as they impact protein denaturation (solubilization).

Original languageEnglish (US)
Pages (from-to)11719-11731
Number of pages13
JournalJournal of Physical Chemistry B
Volume117
Issue number39
DOIs
StatePublished - Oct 3 2013
Externally publishedYes

Fingerprint

methyl chloride
Molecular orientation
Guanidine
Vapors
vapors
aqueous solutions
Cations
cations
Positive ions
Liquids
liquids
surface water
surface stability
Water
air
Air
biopolymer denaturation
rings
Protein folding
folding

ASJC Scopus subject areas

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

Cite this

Liquid-Vapor interfacial properties of aqueous solutions of guanidinium and methyl guanidinium chloride : Influence of molecular orientation on interface fluctuations. / Ou, Shuching; Cui, Di; Patel, Sandeep.

In: Journal of Physical Chemistry B, Vol. 117, No. 39, 03.10.2013, p. 11719-11731.

Research output: Contribution to journalArticle

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