Catalysis by polymer complexes. I. Enhanced esterolytic reactivity of hydroxamate–polymer complexes

Toyoki Kunitake, Seiji Shinkai, Sumio Hirotsu

Research output: Contribution to journalArticle

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Abstract

N‐methylmyristohydroxamic acid (1) bound to polymer micelles of laurylated poly(2‐ and 4‐vinylpyridines) (lauryl group contet: 2VP‐L, 30 mol%; 4VP‐L, 33 mol%) quantitatively reacted with p‐nitrophenyl acetate (NpAc) within a few seconds at 30°C, pH 8.95. Second order rate constants ka were 34,000 M−1 sec−1 for 1–2VP‐L and 11,400 M−1 sec−1 for 1–4VP‐L at μ = 0.5, and they were pronouncedly improved by a decrease in ionic strength (ka = 27,500–80,200 M−1 sec−1 at μ = 0.08). In contrast, poly(N‐ethyl‐4‐vinylpyridinium bromide) hardly affected the nucleophilicity of the hydroxamate ion. Therefore, the enhancement was considered to be associated with some micellar characteristics. Typical saturation phenomena of the reaction rate were observed for p‐nitrophenyl hexanoate (NpOCOPe) and 3‐nitro‐4‐acetoxybenzoic acid (NpAcCOOH). It was suggested that binding of NpOCOPe is caused by the hydrophobic interaction, while that of NpAcCOOH is probably induced by the electrostatic interaction. It is demonstrated that the cationic polymer micelle enormously activates the bound hydroxamate anion, and these complexes would be of much interest as a biomimetic system for enzyme catalysis.

Original languageEnglish
Pages (from-to)1143-1153
Number of pages11
JournalBiopolymers
Volume15
Issue number6
DOIs
Publication statusPublished - Jun 1976

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Micelles
Catalysis
Polymers
Biomimetics
Acids
Coulomb interactions
Ionic strength
Static Electricity
Bromides
Hydrophobic and Hydrophilic Interactions
Osmolar Concentration
Reaction rates
Anions
Rate constants
Acetates
Negative ions
Enzymes
Ions
hexanoic acid

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Biomaterials
  • Organic Chemistry

Cite this

Catalysis by polymer complexes. I. Enhanced esterolytic reactivity of hydroxamate–polymer complexes. / Kunitake, Toyoki; Shinkai, Seiji; Hirotsu, Sumio.

In: Biopolymers, Vol. 15, No. 6, 06.1976, p. 1143-1153.

Research output: Contribution to journalArticle

Kunitake, Toyoki ; Shinkai, Seiji ; Hirotsu, Sumio. / Catalysis by polymer complexes. I. Enhanced esterolytic reactivity of hydroxamate–polymer complexes. In: Biopolymers. 1976 ; Vol. 15, No. 6. pp. 1143-1153.
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AB - N‐methylmyristohydroxamic acid (1) bound to polymer micelles of laurylated poly(2‐ and 4‐vinylpyridines) (lauryl group contet: 2VP‐L, 30 mol%; 4VP‐L, 33 mol%) quantitatively reacted with p‐nitrophenyl acetate (NpAc) within a few seconds at 30°C, pH 8.95. Second order rate constants ka were 34,000 M−1 sec−1 for 1–2VP‐L and 11,400 M−1 sec−1 for 1–4VP‐L at μ = 0.5, and they were pronouncedly improved by a decrease in ionic strength (ka = 27,500–80,200 M−1 sec−1 at μ = 0.08). In contrast, poly(N‐ethyl‐4‐vinylpyridinium bromide) hardly affected the nucleophilicity of the hydroxamate ion. Therefore, the enhancement was considered to be associated with some micellar characteristics. Typical saturation phenomena of the reaction rate were observed for p‐nitrophenyl hexanoate (NpOCOPe) and 3‐nitro‐4‐acetoxybenzoic acid (NpAcCOOH). It was suggested that binding of NpOCOPe is caused by the hydrophobic interaction, while that of NpAcCOOH is probably induced by the electrostatic interaction. It is demonstrated that the cationic polymer micelle enormously activates the bound hydroxamate anion, and these complexes would be of much interest as a biomimetic system for enzyme catalysis.

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