Properties of the Interface Between Two Immiscible Electrolytes in the Presence of Proteins

Abstract

The influence of adsorbed proteins on electrochemical properties of the nitrobenzene‐aqueous interface has been investigated using cyclic voltammetric and impedance techniques. Upon addition of 4 μg/ml ovalbumin cyclic voltammetric normalΔEP values for Cs+ transfer shifted from nearly temperature independent reversible values to more temperature‐dependent irreversible values. These effects were especially pronounced at lower temperatures and suggested formation of a surface film. The cyclic voltammetry of a wide range of concentrations of bovine serum albumin (BSA) in base L/L electrolytes was also studied. Interfacial ac impedance measurements indicated an increase in diffuse layer capacitance accompanied initial BSA adsorption. At high protein concentrations, an adsorbed phase was formed which facilitates faradaic transfer of ions across an otherwise blocked interface.

Voltammetry of proteins at liquid–liquid interfaces

“…Early studies of the behaviour of proteins at the ITIES were reported by Vanysek and colleagues, [34][35][36] in which proteins were examined within a programme to assess the behaviour of biological molecules in general. In these studies, the main findings were that proteins such as ovalbumin, colicine E 3 , and bovine serum albumin (BSA) form adsorbed layers at the ITIES.…”

“…These layers were studied by cyclic voltammetry and impedance methods and revealed that simple ion transfer reactions were inhibited (e.g. transfer of Cs + across the ITIES between water and NB), 35 as shown in Fig 2. Here, the experimental arrangement was that of a large interface (i.e. millimetre or centimetre in scale) set up in a glass cell containing two counter electrode and two reference electrodes.…”

“…These studies by CV of ion transfer inhibition were followed up with impedimetric studies, which showed changes in interfacial capacitance as a function of protein concentration, BSA in this case, 35,36 and providing an indicator of the works to emerge two decades later.…”

Electrochemical behaviour of denatured haemoglobin at the liquid|liquid interface

“…Amongst these, electrochemistry at polarised liquid|liquid interfaces has been used for the investigation of non-redox electrochemistry [2,3] and electroanalytical determination [4] of a range of ions. Recently, a variety of large polycationic molecules have been studied at the liquid|liquid interface, EC09-2006, revised 16Dec2009 2 including dendrimers [5], peptides [6] and proteins [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. We have recently investigated the electrochemical behaviour of haemoglobin [15][16][17], insulin [18] and lysozyme [19] at the liquid | liquid interface.…”

Electroanalytical Opportunities Derived from Ion Transfer at Interfaces between Immiscible Electrolyte Solutions

“…[25c, 100] The first investigations of proteins at the ITIES dates from the 1980s, when Vanysek and colleagues [101] reported the interfacial adsorption of ovalbumin, which was shown to alter a simple IT process. Subsequently, there were few studies of proteins undertaken, in comparison to studies of small molecules.…”