Omanovic S, Roscoe SG
Department of Chemistry, Acadia University, Wolfville, Nova Scotia, B0P 1X0, Canada
J Colloid Interface Sci. 2000 Jul 15;227(2):452-460. doi: 10.1006/jcis.2000.6913.
The electrochemical impedance spectroscopy technique was used to investigate the interfacial behavior of beta-lactoglobulin at an austenitic stainless steel surface over the temperature range 299 to 343 K at an open circuit potential. The electrode/electrolyte interface and corresponding surface processes were successfully modeled by applying an equivalent-electrical-circuit approach. A charge-transfer resistance value was found to be very sensitive to the amount of 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. This was also apparent from the large decrease in the corrosion activation energy (16 kJ mol(-1)) caused by the adsorption of the protein. Adsorption of beta-lactoglobulin onto the stainless steel surface at an open circuit potential 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 beta-lactoglobulin 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. Copyright 2000 Academic Press.
采用电化学阻抗谱技术，在开路电位下，研究了299至343K温度范围内β-乳球蛋白在奥氏体不锈钢表面的界面行为。通过应用等效电路方法，成功模拟了电极/电解质界面及相应的表面过程。发现电荷转移电阻值对吸附蛋白质的量（表面浓度）非常敏感，这表明蛋白质的吸附：（i）通过化学吸附伴随着电荷转移；（ii）影响了腐蚀反应的机理和动力学。蛋白质吸附导致腐蚀活化能大幅降低（16 kJ mol(-1)），这也表明了上述情况。在开路电位下，β-乳球蛋白在不锈钢表面的吸附在所有研究温度下均呈现单峰等温线，且吸附过程可用朗缪尔吸附等温线描述。根据计算出的吸附吉布斯自由能，证实β-乳球蛋白分子强烈吸附在不锈钢表面。焓和熵值表明，分子在吸附时在表面部分展开。发现吸附过程完全由熵变控制。版权所有2000年，学术出版社。
