氨基吡啶修饰碳纳米管的制备及其与辣根过氧化酶的相互作用

用重铬酸钾氧化法获得了表面羧基化的碳纳米管(MWCNT-COOH), 进一步通过酰胺化反应合成了2-氨基吡啶修饰的碳纳米管(MWCNT-AP). 利用傅里叶变换红外(FT-IR)光谱、核磁共振氢谱(¹H NMR)、X射线光电子能谱(XPS)等对合成的碳纳米管进行了表征. 透射电镜(TEM)结果表明MWCNT-COOH在乙醇等极性溶剂中易于簇集, 而MWCNT-AP 溶液具有良好的分散性和稳定性. 辣根过氧化酶(HRP)可通过物理作用吸附于MWCNT-AP 和MWCNT-COOH表面, 负载量分别为187.5 和153.0 μg·mg^-1. HRP被吸附后, 其Soret 带明显红移, 说明HRP 与MWCNT-AP 或MWCNT-COOH 的结合位点位于血红素辅基的附近. 圆二色谱结果表明MWCNT-AP 对HRP的二级结构也有一定影响. 酶动力学实验结果表明MWCNT-AP 能有效地吸附HRP及其底物3,3',5,5'-四甲基联苯胺(TMB), 并使HRP的酶催化反应最大速率(V_max)显著提高.

Preparation of Aminopyridine Grafted Carbon Nanotube and Its Interaction with Horseradish Peroxidase

Carboxylic-functionalized multiwalled carbon nanotube (MWCNT-COOH) is obtained by oxidation with potassium bichromate and further modification by amide condensation afforded aminopyridine-grafted MWCNT (MWCNT-AP). The MWCNT-AP was characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (¹H-NMR) and X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) results suggest that MWCNTCOOH aggregates in ethanol and that MWCNT-AP is stable and well dispersed in solution. Horseradish peroxidase (HRP) physically adsorbed onto the surfaces of MWCNT-AP and MWCNT-COOH and the adsorption amounts were 187.5 and 153.0 μg·mg^-1, respectively. UV-Vis spectra showed that the Soret band of HRP red-shifted markedly after adsorption onto MWCNT-AP or MWCNT-COOH indicating that the binding site of MWCNT-AP or MWCNT-COOH is near the heme pocket of HRP. Circular dichroism spectral results demonstrate that the secondary structure of HRP is influenced by MWCNT-AP. Enzyme-kinetic studies show that MWCNT-AP may adsorb HRP and its substrate 3,3',5,5'-tetramethylbenzidine (TMB) effectively, and the maximum reaction rate (V_max) of HRP increases significantly after interaction with MWCNT-AP.