Abstract Immobilizing enzymes on biomimicking monolayer ultrathin films of phospholipids exhibit enhanced enzymatic activities (EAs) useful for biosensing applications. Preparation of such substrates with enzyme Trypsin (TRYP) immobilized in dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) matrix with enhanced and sustained enzymatic activity is a real challenge, as the isoelectric point of TRYP is reported to exist at pH ~ 10.5. This paper reports for the first time a facile procedure to fabricate smart substrates of TRYP entrapped in the DPPC monolayer using Langmuir–Blodgett (LB) technique. The incorporation of TRYP into DPPC monolayer at the air–water interface has been demonstrated from adsorption kinetics (π – t), room temperature surface pressure–area (π – A) isotherm plot and compressibility (β – π) studies. Circular dichroism (CD) and Grazing angle IR (GAIR) spectra signify changes in the secondary structure of incubated TRYP when immobilized in DPPC monolayer. Improved and sustained EA of TRYP upon its incubation on the organized monolayer LB films of DPPC has been observed. The reason behind such improvement in the EA of immobilized TRYP has also been suggested. The as fabricated substrates of immobilized TRYP can be used to sense soy milk, soy yoghurt, mayonnaise, meringue etc. using Azocasein as the protease substrate.

中文翻译：

---

固定在 DPPC 的 Langmuir Blodgett 膜中的胰蛋白酶的持续和改进的酶活性：一种用于检测偶氮酪蛋白的快速酶传感器

摘要 在仿生单层磷脂超薄膜上固定酶表现出增强的酶活性 (EA)，可用于生物传感应用。用固定在二棕榈酰-sn-甘油-3-磷酸胆碱 (DPPC) 基质中且具有增强和持续酶活性的胰蛋白酶 (TRYP) 来制备此类底物是一项真正的挑战，因为据报道 TRYP 的等电点存在于 pH ~ 10.5 . 本文首次报道了一种使用 Langmuir-Blodgett (LB) 技术制造包裹在 DPPC 单层中的 TRYP 智能基板的简便程序。吸附动力学 (π - t)、室温表面压力 - 面积 (π - A) 等温线图和可压缩性 (β - π) 研究证明了 TRYP 在空气 - 水界面处与 DPPC 单层的结合。圆二色性 (CD) 和掠角红外 (GAIR) 光谱表示固定在 DPPC 单层中时孵化的 TRYP 二级结构的变化。已经观察到在 DPPC 的有组织的单层 LB 膜上孵育后，TRYP 的 EA 得到改善和持续。还提出了固定化 TRYP EA 的这种改进背后的原因。制备的固定化 TRYP 底物可用于以偶氮酪蛋白为蛋白酶底物的豆奶、大豆酸奶、蛋黄酱、蛋白酥皮等。