Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan.
Langmuir. 2011 Jun 21;27(12):7595-602. doi: 10.1021/la201496j. Epub 2011 May 24.
Stearic acid (SA) and octadecylamine (ODA) monolayers at the air/liquid interface were used as template layers to adsorb glucose oxidase (GOx) from aqueous solution. The effect of the template monolayers on the adsorption behavior of GOx was studied in terms of the variation of surface pressure, the evolution of surface morphology observed by BAM and AFM, and the conformation of adsorbed GOx. The results show that the presence of a template monolayer can enhance the adsorption rate of GOx; furthermore, ODA has a higher ability, compared to SA, to adsorb GOx, which is attributed to the electrostatic attractive interaction between ODA and GOx. For adsorption performed on a bare surface or on an SA monolayer, the surface pressure approaches an equilibrium value (ca. 8 mN/m) after 2 to 3 h of adsorption and remains nearly constant in the following adsorption process. For the adsorption on an ODA monolayer, the surface pressure will increase further 1 to 2 h after approaching the first equilibrium pressure, which is termed the second adsorption stage. The measurement of circular dichroism (CD) spectroscopy indicates that the Langmuir-Blodgett films of adsorbed GOx transferred at the first equilibrium state (π = 8 mN/m) have mainly a β-sheet conformation, which is independent of the type of template monolayers. However, the ODA/GOx LB film transferred at the second adsorption stage has mainly an α-helix conformation. It is concluded that the specific interaction between ODA and GOx not only leads to a higher adsorption rate and adsorbed amount of GOx but also induces a conformation change in adsorbed GOx from β-sheet to α-helix. The present results indicate that is possible to control the conformation of adsorbed protein by selecting the appropriate template monolayer.
硬脂酸（SA）和十八烷基胺（ODA）单层在气/液界面用作模板层，从水溶液中吸附葡萄糖氧化酶（GOx）。从表面压力的变化、BAM 和 AFM 观察到的表面形貌的演变以及吸附 GOx 的构象等方面研究了模板单层对 GOx 吸附行为的影响。结果表明，模板单层的存在可以提高 GOx 的吸附速率；此外，与 SA 相比，ODA 具有更高的吸附 GOx 的能力，这归因于 ODA 和 GOx 之间的静电吸引相互作用。对于在裸表面或 SA 单层上进行的吸附，在吸附 2 至 3 小时后，表面压力达到平衡值（约 8 mN/m），并在随后的吸附过程中基本保持不变。对于在 ODA 单层上的吸附，在接近第一平衡压力后 1 至 2 小时，表面压力将进一步增加，这称为第二吸附阶段。圆二色性（CD）光谱测量表明，在第一平衡状态（π = 8 mN/m）下转移的吸附 GOx 的 Langmuir-Blodgett 膜主要具有β-折叠构象，这与模板单层的类型无关。然而，在第二吸附阶段转移的 ODA/GOx LB 膜主要具有α-螺旋构象。结论是，ODA 和 GOx 之间的特异性相互作用不仅导致 GOx 的吸附速率和吸附量更高，而且还导致吸附 GOx 的构象从β-折叠变为α-螺旋。这些结果表明，可以通过选择适当的模板单层来控制吸附蛋白质的构象。
