Investigation of metal ion interaction with a lipid cubic phase using electrochemical impedance spectroscopy

Mohammad Yaser Khani Meynaq; Kenichi Shimizu; Mahdi Shahmohammadi Aghbolagh; Solomon Tesfalidet; Britta Lindholm-Sethson

doi:10.1016/j.jcis.2016.07.053

Investigation of metal ion interaction with a lipid cubic phase using electrochemical impedance spectroscopy

J Colloid Interface Sci. 2016 Nov 15:482:212-220. doi: 10.1016/j.jcis.2016.07.053. Epub 2016 Jul 21.

Authors

Mohammad Yaser Khani Meynaq¹, Kenichi Shimizu², Mahdi Shahmohammadi Aghbolagh¹, Solomon Tesfalidet¹, Britta Lindholm-Sethson³

Affiliations

¹ Department of Chemistry, Umeå University, SE 90187 Umeå, Sweden.
² Department of Chemistry, Umeå University, SE 90187 Umeå, Sweden; Physical and Theoretical Chemistry Laboratory, Department of Chemistry, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom.
³ Department of Chemistry, Umeå University, SE 90187 Umeå, Sweden. Electronic address: britta.sethson@chem.umu.se.

PMID: 27505274
DOI: 10.1016/j.jcis.2016.07.053

Abstract

Hypothesis: Electrochemical impedance spectroscopy, EIS, can be used as a complementary technique to investigate ion interaction with the headgroup region in the aqueous channels of a lipid cubic phase, LCP.

Experiments: A freestanding membrane made of monoolein LCP was formed by filling a small aperture that separates two cell compartments. The cell compartments were filled with electrolyte solutions at two different ionic strengths: i.e.: 10 and 100mM, of KCl, CsBr and CaCl2. Electrochemical impedance spectroscopy was recorded between two platinum electrodes that were present at each side of the membrane.

Findings: The membrane resistance and capacitance were estimated from equivalent circuit fitting of the impedance data. It was confirmed that calcium ions interacts strongly with the headgroup region in the aqueous channels giving significantly higher membrane resistances compared to monovalent alkali metal ions. The membrane capacitance with Ca(2+)(aq) in solution was concentration dependent, which for the first time indicates formation of two different cubic phases at these conditions.

Keywords: Calcium; Cesium; Electrochemical impedance spectroscopy; Ionic permeability; Lipid cubic phase; Lipid–ion interactions; Membrane capacitance; Membrane resistance; Monoolein; Potassium.