Kinetic studies of the aminolysis of benzylpenicillin in poly(ethylenimine) showed a complicated rate behaviour owing to the strong substrate-polyelectrolyte interaction. The results have been interpreted by the formation of an unreactive and reactive complex which is converted into the poly(ethylenimmine)penicilloyl amide. In the presence of KCl the PEI behaves as a simple amine and the second order rate constants of the nucleophilic attack on beta-lactam were calculated at various pHs. The Bronsted beta value is consistent with a stepwise mechanism in which the rate determining step is the T± intermediate decomposition in absence of general acid-base catalysis. The poly(ethylenimine) reveals its catalytic ability not only by binding the substrate to the polymer, but also by increasing the reactivity of the reactive complex. A negligible effect on the alkaline hydrolysis of benzylpenicillin was found in the presence of poly (diallyldimethylammonium) chloride. A parallel between poly(ethylenimine) and Human Serum Albumin in the benzylpenicillin aminolysis is proposed.

Cleavage of benzylpenicilline with polyelectrolytes

ARCELLI, ANTONIO;PORZI, GIANNI;SANDRI, MONICA
2005

Abstract

Kinetic studies of the aminolysis of benzylpenicillin in poly(ethylenimine) showed a complicated rate behaviour owing to the strong substrate-polyelectrolyte interaction. The results have been interpreted by the formation of an unreactive and reactive complex which is converted into the poly(ethylenimmine)penicilloyl amide. In the presence of KCl the PEI behaves as a simple amine and the second order rate constants of the nucleophilic attack on beta-lactam were calculated at various pHs. The Bronsted beta value is consistent with a stepwise mechanism in which the rate determining step is the T± intermediate decomposition in absence of general acid-base catalysis. The poly(ethylenimine) reveals its catalytic ability not only by binding the substrate to the polymer, but also by increasing the reactivity of the reactive complex. A negligible effect on the alkaline hydrolysis of benzylpenicillin was found in the presence of poly (diallyldimethylammonium) chloride. A parallel between poly(ethylenimine) and Human Serum Albumin in the benzylpenicillin aminolysis is proposed.
A. Arcelli; R. Cecchi; G. Porzi; M. Sandri
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/10718
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