Department of Chemical Physics, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, PR China 230026.
Langmuir. 2012 Oct 16;28(41):14642-53. doi: 10.1021/la303001j. Epub 2012 Oct 5.
We have systematically investigated the effect of surface wettability on ion-specific adsorption of bovine serum albumin (BSA) by using quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR). The changes in frequency (Δf) and resonance unit (ΔRU) show a nonmonotonous change of the adsorbed amount of BSA as a function of molar fraction of 1-dodecanethiol (x(DDT)) of the self-assembled monolayer at pH 3.8, while the amount of adsorbed protein gradually increases with the x(DDT) at pH 7.4. The small changes of dissipation (ΔD) indicate that BSA molecules form a quite rigid protein layer on the surfaces, which results in only a slight difference in the adsorbed mass between the mass-uptake estimations from the Sauerbrey equation and the Voigt model. The difference in the adsorbed mass between QCM-D and SPR measurements is attributed to the coupled water in the protein layer. On the other hand, specific anion effect is observed in the BSA adsorption at pH 3.8 with the exception of the surface at x(DDT) of 0%, but no obvious cation specificity can be observed at pH 7.4. The ΔD-Δf plots show that the BSA adsorption at pH 3.8 has two distinct kinetic processes. The first one dominated by the protein-surface interactions is an anion-nonspecific process, whereas the second one dominated by the protein structural rearrangements is an anion-specific process. At pH 7.4, the second kinetic process can only be observed at the relatively hydrophobic surfaces, and no cation specificity is observed in the first and second kinetic processes.
我们系统地研究了表面润湿性对牛血清白蛋白（BSA）离子特异性吸附的影响，使用石英晶体微天平（QCM-D）和表面等离子体共振（SPR）。在 pH 3.8 时，随着自组装单分子层中 1-十二硫醇（x(DDT)）摩尔分数的变化，BSA 的吸附量的频率（Δf）和共振单元（ΔRU）呈非单调变化，而在 pH 7.4 时，吸附蛋白的量则逐渐随 x(DDT)增加。耗散（ΔD）的微小变化表明 BSA 分子在表面上形成了相当刚性的蛋白质层，这导致从 Sauerbrey 方程和 Voigt 模型估算的吸附质量之间只有很小的差异。QCM-D 和 SPR 测量之间的吸附质量差异归因于蛋白质层中的耦合水。另一方面，在 pH 3.8 下观察到 BSA 吸附存在特异性阴离子效应，除了 x(DDT)为 0%的表面外，但在 pH 7.4 下则没有明显的阳离子特异性。ΔD-Δf 图表明，BSA 在 pH 3.8 下的吸附有两个明显的动力学过程。第一个由蛋白质-表面相互作用主导的是一个非特异性阴离子过程，而第二个由蛋白质结构重排主导的是一个特异性阴离子过程。在 pH 7.4 时，第二个动力学过程只能在相对疏水的表面上观察到，而在第一个和第二个动力学过程中均没有观察到阳离子特异性。
