Voltammetric behaviour of biological macromolecules at arrays of aqueous|organogel micro-interfaces

Abstract

The behaviour of two biological macromolecules, bovine pancreatic insulin and hen-egg-white lysozyme (HEWL), at aqueous-organogel interfaces confined within an array of solid-state membrane micropores was investigated via cyclic voltammetry (CV). The behaviour observed is discussed in terms of possible charge transferring species and mass transport in the interfacial reaction. Comparison of CV results for HEWL, insulin, and the well-characterised model ion tetraethylammonium cation (TEA(+)) revealed that the biomacromolecules undergo an interfacial reaction comprising biomacromolecular adsorption and facilitated transfer of electrolyte anions from the organic phase to a protein layer on the aqueous side of the interface, whereas TEA(+) undergoes a simple ion transfer process. Evidence for biomacromolecular adsorption on the aqueous side of the micro-interfaces is provided by comparison of the CVs for TEA(+) ion transfer in the presence and absence of the biomacromolecules. Similar experiments in the presence of the low generation polypropylenimine tetraamine dendrimer, (DAB-AM-4), a smaller synthetic molecule, revealed it to be non-adsorbing. The behaviour of biological macromolecules at miniaturised aqueous-organogel interfaces involves adsorption on the aqueous side of the interface and transfer of organic phase electrolyte anions across the interface to associate with the adsorbed biomacromolecule. The data presented support the previously suggested mechanism for biomacromolecular voltammetry at liquid-liquid interfaces, involving adsorption and facilitated ion-transfer of organic electrolyte anions.

Electrochemical behaviour of myoglobin at an array of microscopic liquid–liquid interfaces

“…A range of proteins have been studied at the ITIES in the absence of surfactants and it was found that the proteins did not transfer across the ITIES but adsorbed there and facilitated the transfer of the organic anion to the aqueous phase [24,[26][27][28]. The effect of varying the organic phase anion on the electrochemistry of protamine at the ITIES was extensively studied by Trojanek et al using conductometry, voltammetry and quasi-elastic light scattering [22].…”

“…In recent years there have been many reports on the behaviour and detection of biomolecules at the ITIES. The detection of a range of biomolecules including amino acids [19], heparin [20,21], protamine [22,23], haemoglobin [24,25], lysozyme [26,27], insulin [28], dopamine [29][30][31], noradrenaline [31] and DNA [32] have been reported at the ITIES.…”

Haemoglobin unfolding studies at the liquid–liquid interface

“…The electrochemical behaviour of proteins [9][10][11][12][13][14][15] at the interface between two immiscible electrolyte solutions (ITIES) has been reported recently. Proteins adsorb at the interface and assist the transfer of anions from the organic phase electrolyte to the aqueous phase.…”

Studying the ion transfer across liquid interface of thin organic-film-modified electrodes in the presence of glucose oxidase

“…1. The adsorption of the enzyme is mainly driven by the lipophylic interactions of the enzyme with the organic solvent [26][27][28][29][30][31][32][33][35][36][37]. It is plausible to assume that the enzyme molecules are oriented at the liquid interface, with the negatively charged surface leaning toward the aqueous phase.…”

“…In recent years, there has been an increased attention in the study of proteins at L|L interfaces, mainly by means of the four-electrode configuration setup [26][27][28][29][30][31][32][33]. Of particular interest are electron-transfer reactions across the L|L interfaces involving redox-active enzymes.…”