Huang Rong, Hu Naifei
Department of Chemistry, Beijing Normal University, Beijing 100875, PR China.
Biophys Chem. 2003 May 1;104(1):199-208. doi: 10.1016/s0301-4622(02)00367-8.
This paper reports the direct voltammetry of horseradish peroxidase (HRP) incorporated in amphiphilic polyacrylamide (PAM) films modified on pyrolytic graphite (PG) electrodes. Cyclic voltammetry of HRP-PAM films showed a pair of well-defined, nearly reversible peaks at approximately -0.33 V vs. SCE in pH 7.0 buffers, characteristic of HRP heme Fe(III)/Fe(II) redox couple. The PAM films in solution contained large amounts of water and formed a hydrogel, and provided a favorable microenvironment for HRP and facilitated its direct electron transfer with underlying PG electrodes. The apparent heterogeneous electron transfer rate constant (k(s)) and formal potential (E*') were estimated by fitting the data of square wave voltammetry (SWV) with the non-linear regression analysis. UV-vis absorption spectra demonstrated that HRP in PAM films retained its secondary structure similar to its native state. The embedded HRP in PAM films showed the electrocatalytic activity to various substrates such as nitrite, oxygen and hydrogen peroxide. The possible mechanism of catalytic reaction of H(2)O(2) with HRP-PAM films was proposed.
本文报道了辣根过氧化物酶（HRP）在热解石墨（PG）电极上修饰的两亲性聚丙烯酰胺（PAM）膜中的直接伏安法。HRP-PAM膜的循环伏安法在pH 7.0缓冲液中相对于饱和甘汞电极（SCE）在约-0.33 V处显示出一对定义明确、近乎可逆的峰，这是HRP血红素铁（III）/铁（II）氧化还原对的特征。溶液中的PAM膜含有大量水分并形成水凝胶，为HRP提供了有利的微环境，并促进了其与底层PG电极的直接电子转移。通过非线性回归分析拟合方波伏安法（SWV）数据，估算了表观异相电子转移速率常数（k(s)）和形式电位（E*'）。紫外可见吸收光谱表明，PAM膜中的HRP保留了与其天然状态相似的二级结构。PAM膜中嵌入的HRP对亚硝酸盐、氧气和过氧化氢等各种底物表现出电催化活性。提出了H(2)O(2)与HRP-PAM膜催化反应的可能机制。
