Adsorption of Soft and Hard Proteins onto OTCEs underthe Influence of an External Electric Field.

The adsorption behavior of hard andsoft proteins under the effectof an external electric field was investigated by a combination ofspectroscopic ellipsometry and molecular dynamics (MD) simulations.Optically transparent carbon electrodes (OTCE) were used as conductive,sorbent substrates. Lysozyme (LSZ) and ribonuclease A (RNase A) wereselected as representative hard proteins, whereas myoglobin (Mb),α-lactalbumin (α-LAC), bovine serum albumin (BSA), glucoseoxidase (GOx), and immunoglobulin G (IgG) were selected to representsoft proteins. In line with recent publications from our group, theexperimental results revealed that while the adsorption of all investigatedproteins can be enhanced by the potential applied to the electrode,the effect is more pronounced for hard proteins. In contrast withthe incomplete monolayers formed at open-circuit potential, the applicationof +800 mV to the sorbent surface induced the formation of multiplelayers of protein. These results suggest that this effect can be relatedto the intrinsic polarizability of the protein (induction of dipoles),the resulting surface accessible solvent area (SASA), and structuralrearrangements induced upon the incorporation on the protein layer.The described experiments are critical to understand the relationshipbetween the structure of proteins and their tendency to form (underelectric stimulation) layers with thicknesses that greatly surpassthose obtained at open-circuit conditions. [ABSTRACT FROM AUTHOR]