Interfacial complexes between a protein and lipophilic ions at an oil-water interface.

Rune A Hartvig, Manuel A Méndez, Marco van de Weert, Lene Jorgensen, Jesper Østergaard, Hubert H Girault, Henrik Jensen

Index: Anal. Chem. 82(18) , 7699-705, (2010)

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Abstract

The interaction between an intact protein and two lipophilic ions at an oil-water interface has been investigated using cyclic voltammetry, impedance based techniques and a newly developed method in which the biphasic oil-water system is analyzed by biphasic electrospray ionization mass spectrometry (BESI-MS), using a dual-channel electrospray emitter. It is found that the protein forms interfacial complexes with the lipophilic ions and that it specifically requires the presence of the oil-water interface to be formed under the experimental conditions. Furthermore, impedance based techniques and BESI-MS with a common ion to polarize the interface indicated that the Galvani potential difference across the oil-water interface significantly influences the interfacial complexation degree. The ability to investigate protein-ligand complexes formed at polarized liquid-liquid interfaces is thus a new analytical method for assessing potential dependent interfacial complexation using a structure elucidating detection principle.