engleski

Effect of Protein Adsorption at a Stainless Steel Surface: Comparison of Protein Surface Denaturation

The adsorption behaviour of holo-a-lactalbumin (a-LA) on high purity austenitic 316L stainless steel and its effect on the state of the electrode surface have been studied over the temperature range 299 to 343 K. Cyclic voltammetry measurements were made to characterize the electrochemical behaviour of the electrode and to investigate the effects of surface roughness on the surface dissolution stability. the electrochemical impedance spectroscopy technique was used to investigate the interfacial behaviour of a-LA at the stainless steel surface at an open circuit potential. the electrode/electrolyte interface and corresponding surface processes were successfully modeled by applying an equivalent-electrical-circuit approach. The charge transfer resistance value was found to be very sensitive to the amount of the adsorbed protein (surface concentration), thus indicating that the adsorption of the protein (i) was accompanied by the transfer of the charge, via chemisorption, and (ii) influenced the mechanism and kinetics of the corrosion reaction. Adsorption of a-LA onto the stainless steel surface at an OCP resulted in a unimodal isotherm at all the temperatures studied, and the adsorption process was described with a Langmuir adsorption isotherm. From the calculated Gibbs free energies of adsorption it was confirmed that a-LA molecules adsorb strongly onto the stainless steel surface. The enthalpy and entropy values indicated that the molecule partially unfolds at the surface upon adsorption. The adsorption process was found to be entirely governed by the change in entropy. A comparison is made with results obtained under similar experimental conditions using other globular proteins ; bovine serum albumin (1) and b-lactoglobulin (2). The difference in behaviour is explained on the basis of protein intramolecular interactions.

Protein Adsorption; Holo-a-lactalbumin

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