Dispersion enzyme-catalyzed

Uyama and Kobayashi et al. [115,116] were first to prepare nearly mono-disperse sub-micron polyphenol particles by the enzyme-catalyzed dispersion polymerization of phenol andp-phenylphenol in a mixture of 1,4-dioxane and phosphate buffer using a water-soluble polymer as stabilizer (such as PVME, PVA, and PEG). 

Figure 6.11 shows the activity of an artificial enzyme can be controlled based on the phase behavior of a lipid bilayer. The catalytic site for hydrolysis was supplied by a monoalkyl azobenzene compound with a histidine residue which was buried in the hydrophobic environment of a hpid bilayer matrix formed using a dialkyl ammonium salt. Azobenzene compound association depended on the state of the matrix bilayer. The azobenzene catalyst aggregated into clusters when the bilayer matrix was in a gel state. In contrast, the azobenzene derivative can be dispersed into the liquid crystalhne phase of the bilayer matrix above its phase transition temperature. This bilayer-type artificial enzyme catalyzed the hydrolysis of a Z-phenylalanine p-nitrophenyl ester. The activation energy for this reaction in the gel state is twice as large as that observed in the hquid crystalline state. The clustering of the catalysts upon phase separation suppress their catalytic activity, probably due to the disadvantageous electrostatic environment around the catalysts and the suppressed substrate diffusion. This activity control is unique to such molecular assembhes. 

Chaudhary, A. K., Beckman, E. J., and Russell, A. J., Rational control of polymer molecular weight and dispersity during enzyme-catalyzed polyester synthesis in supercritical fluids, J. Am. Chem. Soc., 117, 3728-3733, 1995. 

Polypyrroles (PPy s) are formed by the oxidation of pyrrole or substituted pyrrole monomers. In the vast majority of cases, these oxidations have been carried out by either (1) electropolymerization at a conductive substrate (electrode) through the application of an external potential or (2) chemical polymerization in solution by the use of a chemical oxidant. Photochemically initiated and enzyme-catalyzed polymerization routes have also been described but are less developed. These various approaches produce polypyrrole (PPy) materials with different forms—chemical oxidations generally produce powders, whereas electrochemical synthesis leads to films deposited on the working electrode, and enzymatic polymerization gives aqueous dispersions. The conducting polymer products also possess different chemical/electrical properties. These alternative routes to PPy s are therefore discussed separately in this chapter. 

Polypyrrole and many of its derivatives can be synthesized via simple chemical or electrochemical methods [120]. Photochemically initiated and enzyme-catalyzed polymerization routes have also been described but less developed. Different synthesis routes produce polypyrrole with different forms chemical oxidations generally produce powders, while electrochemical synthesis leads to films deposited on the working electrode and enzymatic polymerization gives aqueous dispersions [Liu. Y. C, 2002, Tadros. T. H, 2005 and Wallace. G. G, 2003]. As mentioned above the electrochemical polymerization method is utilized extensively for production of electro active/conductive films. The film properties can be easily controlled by simply varying the electrolysis conditions such as electrode potential, current density, solvent, and electrolyte. It also enables control of thickness of the polymers. Electrochemical synthesis of polymers is a complex process and various factors such as the nature and concentration of monomer/electrolyte, cell conditions, the solvent, electrode, applied potential and temperature, pH affects the yield and the quality of the film... 

The conditions required to favor esterification can be obtained in different manners. It is possible to add a water-miscible solvent that will lower the water concentration and increase the solubility of organic substrates and products. It is also possible to work in a two-phase system with a non-water-miscible solvent, which will serve as a reservoir for the substrates and products. This can be achieved either with macroscopic phases or with highly dispersed systems such as reversed micelles. In the above-mentioned cases, the enzyme-catalyzed reaction takes place in the aqueous phase or at the phase interface. The enzyme can be dissolved in this phase or immobilized by covalent attachment to a solid carrier... 

Enzymes are chiral catalysts. Some are completely specific for the catalysis of the reaction of only one particular compound, whereas others are less specific and catalyze similar reactions of a family of compounds. An enzyme catalyzes a biological reaction of molecules by first positioning them at a binding site on its surface. These molecules may be held at the binding site by a combination of hydrogen bonds, electrostatic attractions, dispersion forces, or even temporary covalent bonds. 

Deposition on fibers or fabrics Vapor phase deposition Deposition in nanoscale matrices Photochemically initiated polymerization Enzyme-catalyzed polymerization Polymerization using electron acceptors Miscellaneous polymerization methods Routes to more processible polyanilines Emulsion polymerization Colloidal polyaniline dispersions Substituted polyanilines... 

The rapid development of biotechnology during the 1980s provided new opportunities for the application of reaction engineering principles. In biochemical systems, reactions are catalyzed by enzymes. These biocatalysts may be dispersed in an aqueous phase or in a reverse micelle, supported on a polymeric carrier, or contained within whole cells. The reactors used are most often stirred tanks, bubble columns, or hollow fibers. If the kinetics for the enzymatic process is known, then the effects of reaction conditions and mass transfer phenomena can be analyzed quite successfully using classical reactor models. Where living cells are present, the growth of the cell mass as well as the kinetics of the desired reaction must be modeled [16, 17]. 

Not all ILs are good solvents for proteins, however. There is the interesting example of lipase. Lipase is soluble in both aqueous and organic solvents, so it can be easily solubilized in ILs. Certain lipases even become dispersed or dissolved in some ILs. Since lipase is a very stable enzyme, it catalyzes the hydrolysis of lipids. Enzymatic activity is reported to be maintained in ILs [1]. There is not much published on the solubilization of biomaterials in ILs. In the present chapter we introduce a procedure to use in solubilizing biomaterials in ILs. First we consider the preparation of the IL, and then the chemical modification of biomaterials suitable for dissolution. We have found this procedure helpful when we tried to use electrochemicaUy active biomaterials in ILs. 

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