PEROXIDASE,HEMATIN, AND PEGYLATED-HEMATIN CATALYZED VINYL POLYMERIZATIONS IN WATER

Horseradish peroxidase-, hematin- and pegylated-hematin mediated polymerization of sodium styrene sulfonate and sodium acrylate in water is reported. Molecular weight and yields were influenced by the concentrations of hydrogen peroxide and initiator, 2,4-pentanedione. Hematin and pegylated-hematin were studied in lieu of peroxidase at pH 11.0 and 7.0 in aqueous solution, respectively. Polymer with a high molecular weight (Mn = 223,520) was formed when the pegylated-hematin was used as the catalyst. The results demonstrate vinyl polymerizations in an all aqueous process in high yield and molecular weight catalyzed by peroxidase as well as biomimetic catalysts.     

Micellar histidinate hematin complex as an artificial peroxidase enzyme model: Voltammetric and spectroscopic investigations

The UV–vis spectrophotometry and cyclic voltammetry were employed to investigate the incorporation of hematin into histidine (His) in a micellar environment of sodium dodecyl sulfate (SDS). Histidine undergoes a reduction process on silver electrode, while, hematin and sodium dodecyl sulfate are not electroreactive species on this electrode. Electrochemistry of twine-by-twine mixture of His, hematin and SDS on silver electrode shows that the peak potential of His in the presence of SDS or hematin shifts negatively which indicates the interaction of SDS and hematin with His. The interaction of SDS and hematin with His was also confirmed using spectrophotometric measurements. However, the peak potential of His on silver electrode shifts positively in the presence of both SDS and hematin which indicates that in a triple-component solution of His–hematin–SDS a unique species is formed and is electroreactive on silver electrode. In this context, this triple-component solution represents unique absorption band in UV–vis spectra, which is related to the formation of a unique structure of a hemoprotein-like biomimetic catalyst. The catalytic activity of this artificial enzyme formed in triple-component solution was examined with respect to hydrogen peroxide and the apparent Michaelis–Menten (K_m) and catalytic rate (k_cat) constants were evaluated to be 3.31 μM and 0.043 s⁻¹, respectively.     

血红素-琼脂糖修饰电极的电化学和电催化性质研究

用循环伏安法研究了血红素-琼脂糖凝胶修饰电极在水和有机溶剂/水混合溶液中的电化学和催化还原过氧化物的性质。包埋在琼脂糖水凝胶膜中的血红素能与电极之间直接传递电子,且具有过氧化物模拟酶的特性,能快速地催化还原过氧化物,可用于这些物质的定量检测。     

Biomimetic Synthesis of Water Soluble Conductive Polypyrrole and Poly(3,4‐Ethylenedioxythiophene)

Abstract

A novel biomimetic method for the synthesis of conducting molecular complexes of polypyrrole (PPYR) and poly(3,4‐ethylenedioxythiophene) (PEDOT) in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS) is presented. A poly(ethylene glycol) modified hematin (PEG‐Hematin) was used to catalyze the polymerization of pyrrole (PYR) and 3,4‐ethylenedioxythiophene (EDOT) in the presence of SPS to form PPYR/SPS and PEDOT/SPS complexes. UV‐VIS, FT‐IR, and electrical conductivity studies for all complexes indicated the presence of a stable and electrically conductive form of these polymers. Furthermore, the presence of SPS in this complex provides a unique combination of properties such as processability and water‐solubility.     

A New Approach to Catalyze Template Polymerization of Aniline Using Electrostatically Multilayered Hematin Assemblies

Abstract

In this work, we describe a new approach to catalyze the template polymerization of conducting polyaniline (Pani). Electrostatic layer‐by‐layer (ELBL) self‐assembly of a polyelectrolyte and a biomimetic catalyst, hematin has been utilized to construct a nanocomposite film catalyst. Poly(dimethyl diallylammonium chloride) (PDAC) and hematin have been used as polycation and counter anions, respectively. The absorption spectra by UV‐VIS‐NIR spectroscopy showed that a conductive form Pani was formed, not only as a coating on the surface of the ELBL composites, but was also formed in solution. Furthermore, it was found that the reaction rate was affected by pH and concentration of hematin in the multilayers. The feasibility of controlled desorption of hematin molecules from the LBL assembly was explored and demonstrated by changing pH and hematin concentration. It is believed that hematin sandwiched between positively charged polyelectrolytes in the composite films was slowly released into the solutions and then used to catalyze the template polymerization of aniline with SPS, resulting in a water soluble form of Pani. The polymerization rate of aniline in solution was enhanced with decreasing pH of the solutions due to increased desorption of hematin nanoparticles from the multilayers. These ELBL hematin assemblies demonstrated both a way to functionalize surfaces with conductive Pani and a potential method of reusability of the catalyst for improved cost effectiveness.     

基于聚3,4-乙撑二氧噻吩和1-芘丁酸构建的新型铁卟啉仿生传感器及其对邻苯二酚的催化研究

利用π-π共轭效应,将1-芘丁酸(PBA)与导电高聚物聚3,4-乙撑二氧噻吩(PEDOT)相连,并通过Zr4+与羧基形成的配位键将羟基铁卟啉(Hematin)与PBA相连接,将Hematin固定于电极上,构建出一种制备过程简单的新型传感器(GCE/PEDOT/PBA/Hematin)。为了检验这种仿生传感器的稳定性和灵敏度,通过循环伏安法(CV)、交流阻抗法(EIS)和时间电流曲线法(i-t)等各种技术,将其应用于电化学检测中。CV扫描证实在充分除氧的PBS缓冲液中,GCE/PEDOT/PBA/Hematin出现一对准可逆的氧化还原峰,其电子转移速率常数约为4.8 s!1,说明聚合于电极上的PEDOT膜增加了Hematin的电子转移速率。另外,通过i-t曲线检测邻苯二酚,在邻苯二酚浓度5×10!7~2×10!4mol/L范围内,其与催化电流强度呈线性相关,i=0.018C+0.006(R=0.9998),检测灵敏度为0.258μA(μmol·cm2),检出限为0.33 nmol/L(S/N=3),证明此仿生传感器稳定,简单且灵敏度高。     

Kinetic Studies of Acylation of Polyethylene Glycol Hydroxyl Groups

The reactivity of polyethylene glycol (PEG) hydroxyl groups was studied by acylation with benzoyl bromide in the presence of a catalyst (tributylamine). The reaction rate constants were calculated for all forms of H-complexes in PEG solutions in CCl₄ and dioxane.