Metal ion‐promoted hydrolyses of ligand esters in the presence of polycarboxylates

Takeishi, Makoto; Watanabe, Toshio; Niino, Shogo; Hayama, Shigeru

doi:10.1002/pol.1980.170181017

Cited by 4 publications

References 16 publications

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Catalytic Properties of Polymers in Solutions

Bekturov¹,

Kudaibergenov²

1997

Catalysis by Polymers

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Polymers are increasingly being used as active components in synthesis and catalysis [I -121. Three basic directions of polymer application are cited as follows:( 1 ) use of polymers as reagents; (2) application of functional groups of polymers as catalysts; and (3) use of polymers as supports. Catalysis by functional groups of macromolecules has attracted scientists' attention owing to the rapid development of enzyme catalysis. High catalytic activity of enzymes is attributed to the broad variety of their particular functional groups which enables their involvement in multiple interactions. The main limitation for using polymers in enzyme catalysis is their lack of a diverse functional group. Consequently, complex enzyme functions cannot yet be realized by synthetic analogues. Nevertheless, the molecular nature of proteins has prompted many scientists to focus on catalytic systems based on synthetic polymers as simple model proteins, metalloenzymes and ferments.This chapter presents various examples of enzyme catalysis by polymers including ester hydrolysis, decomposition of hydrogen peroxide, oxidation of disubstituted phenols and hydroquinone, interfacial catalysis and other types of reaction. Because metal ions (Fe, Zn, Cu. Mn, Co, erc.) are often involved as coferments during enzyme catalysis, some examples illustrating their catalytic action are also given. The catalytic activity of polymeric coordination compounds is shown to depend on the strength of the ligand-metal bond.

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Catalytic Properties of Polymers in Solutions

Bekturov¹,

Kudaibergenov²

1997

Catalysis by Polymers

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Esterolytic action of poly(vinyl alcohol)‐copper(II) complex

Takeishi

Ueda

Hayama

1981

Makromol. Chem., Rapid Commun.

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Some hydrolytic enzymes require a metal ion as a cofactor for their action. In those enzymatic processes a protein-metal ion complex catalyzes the reactions. We have been investigating the esterolytic action of synthetic polymer-metal ion complexes as models for metalloenzymes I ~ 3). On the other hand, the complex formation of poly(viny1 alcohol) (PVA) with metal ions has been reported4-@.The present communication reports on the catalytic activity of the PVA-Cu(I1) complex in the hydrolysis of 2,4-dinitrophenyl acetate around neutrality. Experimental PartMaterials: The same sample of 2,4-dinitrophenyl acetate was applied as the one used in the previous study2). 4-Acetoxy-3-nitrobenoic acid was prepared according to the method of Over-berger7); m.p. 151 -152OC (Lit.7): m.p. 152T).Poly(viny1 alcohol) (PVA) (from Tokyo Kasei Kogyo Co., Ltd.) was purified by reprecipitation from water/acetone; DP: 1750; degree of saponification: 99,8%. Hydrolyses: Hydrolyses were carried out in ethanol/water (20 vol.-Vo), containing the PVA-Cu(I1) complex. [PVA] = 0,l mol .I-I (based on monomeric unit), [Cu"] = 1 to 7 . mol . I-', and [OH -1 5 1,9 [Cu"]. The complex-containing solutions (3 ml) were placed in quartz cells and kept in a bath at 20°C. A THF solution of 2,4-dinitrophenyl acetate (30 pl) wasadded to one of the cells which was placed in a Shimadzu UV-210 spectrophotometer, thermostated at 20°C. The reaction was followed by measuring the increase in the absorbance of the released 2,4-dinitrophenol at 410 nm. The absorbance of 2,4-dinitrophenolate ion shows a maximum at 360 nm, but the measurement could not be performed at this wave length because of the absorption of the PVA-Cu(1I) complex. The pseudo-first-order kinetic plots were straight lines at the initial stage; however, the plots slightly deviated downwards from the line at conversions > 10%. The observed pseudo-first-order rate constants, kobsd, were calculated from the initial slopes. Results and DiscussionWhen potassium hydroxide is added to an aqueous solution of cupric nitrate, the light blue cupric hydroxide precipitates. In the presence of a sufficient amount of PVA, however, a transparent green solution is obtained, indicating the formation of the PVA-Cu(I1) complex, as previously reported4,".The titration curves in Fig. 1 show that a PVA-Cu(N03),-KOH solution itself functions as a buffer solution in the range of [OH-]/2[Cu2+] = 0,05-0,95, at pH 5,4-6,3. When a cupric nitrate solution is added to a PVA-KOH solution cupric

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Enzyme-Mimetic Polymers

Imanishi

1985

Bioactive Polymeric Systems

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Metal ion‐promoted hydrolyses of ligand esters in the presence of polycarboxylates

Cited by 4 publications

References 16 publications

Catalytic Properties of Polymers in Solutions

Catalytic Properties of Polymers in Solutions

Esterolytic action of poly(vinyl alcohol)‐copper(II) complex

Enzyme-Mimetic Polymers

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