Phenolics functional, peroxidase-catalyzed

The peroxidase-catalyzed polymerization of m-alkyl substituted phenols in aqueous methanol produced soluble phenolic polymers. The mixed ratio of buffer and methanol greatly affected the yields and the molecular weight of the polymer. The enzyme source greatly affected the polymerization pattern of m-substituted monomers. Using SBP catalyst, the polymer yield increased as a function of the bulkiness of the substituent, whereas the opposite tendency was observed when HRP was the catalyst. 

Peroxidase-catalyzed polymerization of phenols has provided a new methodology for functional polymeric materials. 

Peroxidase-Catalyzed Synthesis of Functional Phenolic Polymers... 

Peroxidase-catalyzed polymerization of phenols provided a new methodology for functional polymeric materials. Poly(oxy-2,6-dimethyl-l,4-phenylene) (poly(phenylene oxide), PPO) is widely used as a high-performance engineering... 

This section describes the horseradish peroxidase-catalyzed synthesis of both homo- and copolymers of aromatic polymers based on phenols, naphthols, aniline, and their derivatives. Syntheses of novel optically active polymers are studied by changing the environment in which the enzyme functions, along with the organization of the monomers in the reaction mixture. To this objective, enzyme-catalyzed polymer syntheses are carried out in bulk monophasic conditions in which the solvent is miscible with water, biphasic solvent systems in which the solvents used for the syntheses are not miscible with water, and oil-in-water system in the presence of a detergent called reverse micelles. These experimental approaches are shown schematically in Fig. 4. 

The peroxidase-catalyzed polymerization of phenol and aniline derivatives has shown a lot of potential for the synthesis of new functional polymers under mild conditions, and for the environmentally friendly synthesis of phenol polymers without using toxic formaldehyde, as was shown in the previous paragraphs. The main drawback of this type of synthesis are therefore the cost and the handUng of the enzyme, although peroxidases are widely distributed in nature and HRP is extensively used commercially. 

During the last ten years, many research results have shown that oxidative polymerization catalyzed by peroxidases is a convenient, resource-saving, and environmentally friendly method for synthesizing phenol polymers. In contrast to the conventional synthesis of phenol-formaldehyde resins, the peroxidase-catalyzed polymerization of phenol proceeds under mild reaction conditions (room temperature, neutral pH). The polymerization of toxic phenols has promising potential for the cleaning of wastewaters. Moreover, the polymerization of phenols from renewable resources is expected to attract much attention in times of worldwide demand for the replacement of petroleum-derived raw materials. Besides the environment-protecting aspects of this innovative type of polymerization, the enzyme-catalyzed polymerization represents a convenient method to reahze new types of functional polyaromatic polymers. Phenol polymers made by peroxidase catalysis should have much potential for electronic and optical apphcations. The synthesis of functional phenol polymers is facihtated by the fact that poly-... 

Enzymatic transformations of alkaloids by peroxidases most probably occur by single-step oxidations catalyzed by the HRP-I and HRP-II forms of the enzyme. The catalysis of one-electron oxidations of compounds containing aromatic hydrocarbon, hydrazine, phenol, hydroxamic acid, and amine functional groups has been recently reviewed (45, 58, 82). A brief summary of those HRP reactions that involve functional groups most commonly occurring in alkaloids is presented below. 

Cytochrome c peroxidase (CCP) catalyzes the oxidation of ferrocytochrome c (cyt c). Many site-directed mutagenesis studies have been performed on this enzyme in efforts to better understand and rationally engineer heme peroxidase function [149 -156], Various studies indicate that the large protein substrate cyt c binds to CCP in a different region than smaller substrates [155, 157]. Whereas small substrates such as phenol and aniline are believed to approach the heme from its distal side and bind at the heme edge, cyt c lies much further from the heme, and electron transfer seems to occur from the proximal side [158], The low activity and selectivity exhibited by CCP compared to HRP and CPO is attributed to the limited access by small substrates to the heme [159]. 

Many publications have shown the outstanding potential of the HRP-catalyzed phenol polymerization for the synthesis of functional phenol polymers. An exceptional feature of the peroxidase catalysis is the possibility of polymerizing chemoselectively phenols having double or triple bonds in the side chain. One of the first examples of this feature was the polymerization of 2-(4-hydroxyphenyl)ethyl methacrylate (Scheme 11, 50). The HRP-... 

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