Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States.
Langmuir. 2012 May 1;28(17):6928-34. doi: 10.1021/la3009128. Epub 2012 Apr 19.
The pH effect on adsorbed antibody-binding protein (protein G) orientation on gold (Au) and its adsorption thermodynamic characteristics were investigated using quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS). The adsorbed protein G orientation was measured by binding response of two antibody-antigen systems: the model bovine serum albumin (BSA) and the foodborne pathogen E. coli O157:H7. Surface coverage was not significantly affected by pH, but its orientation was. The most properly oriented protein G for antibody binding was achieved at near-neutral pH. Adsorption was verified by XPS measurements using nitrogen (N) 1s, oxygen (O) 1s, and Au 4p peak heights. Adsorption energetics were determined by van't Hoff and Langmuir kinetic analyses of adsorption data obtained at 296, 303, and 308 K. Large characteristic entropy change of protein adsorption was observed (ΔS° = 0.52 ± 0.01 kcal/mol·K). The adsorption process was not classical physisorption but exhibited chemisorption characteristics based on significant enthalpy change (ΔH° = -25 ± 6 kcal/mol).
采用石英晶体微天平（QCM）和 X 射线光电子能谱（XPS）研究了 pH 值对金（Au）表面吸附抗体结合蛋白（蛋白 G）取向及其吸附热力学特性的影响。通过两种抗体-抗原体系的结合响应来测量吸附蛋白 G 的取向：模型牛血清白蛋白（BSA）和食源性致病菌 E. coli O157:H7。表面覆盖率不受 pH 值影响，但取向受 pH 值影响。在接近中性 pH 值时，蛋白 G 最适合与抗体结合。使用氮（N）1s、氧（O）1s 和 Au 4p 峰高的 XPS 测量验证了吸附作用。通过 van't Hoff 和 Langmuir 动力学分析在 296、303 和 308 K 下获得的吸附数据，确定了吸附能。观察到蛋白吸附的大特征熵变化（ΔS°=0.52±0.01 kcal/mol·K）。吸附过程不是经典的物理吸附，而是基于显著的焓变（ΔH°=-25±6 kcal/mol）表现出化学吸附特征。
