Effective Heterogeneous Hydrolysis of
Phosphodiester by Pyridine-Containing Metallopolymers
Ahmed I. Hanafy, Vasiliki Lykourinou-Tibbs,
Kirpal S. Bisht,* and Li-June Ming*
Inorg. Chim. Acta. 2005, 358, 1247–1252
Abstract: The copper(II) complex
of a simple pyridine- and amide-containing copolymer serves as an effective
catalyst for heterogeneous hydrolysis of the prototypical phosphodiester
substrate bis(p-nitrophenyl)phosphate at pH 8.0 and 25 °C. The
catalysis has a first-order rate constant of kcat = 8.3 × 10–6
s–1, corresponding to a catalytic proficiency
of 75-thousand folds relative to the uncatalyzed hydrolysis with a rate
constant of ko = 1.1 × 10–10
s–1 at pH 8.0. This observation suggests
that polymers can be designed to include various functional groups feasible
for effective metal-centered catalysis of phosphodiester hydrolysis.
Concluding remarks
Cu2+ is unique among first-row transition metal ions in hydrolytic chemistry,
wherein it can activate a few hydrolases (including serralysin and astacin)
to a great extent while show negligible activation toward some other hydrolases
such as carboxypeptidase A and carbonic anhydrase. To gain further understanding
of metal-centered hydrolysis and design more effective hydrolytic catalysts,
it is essential to solve the puzzle about why and why not Cu2+ can activate
these enzyme systems for hydrolysis. We present in this communication the
investigation of the Cu2+ complex of a simple pyridine- and amide-containing
copolymer family that exhibits a significant activity toward phosphodiester
hydrolysis, which provides another model system for
further investigation of Cu2+ -centered hydrolytic chemistry. The simplicity
in the preparation of this 4VpAc copolymer and the high hydrolytic activity
of its Cu2+ complex suggest potential application of this family of metallopolymers
in hydrolytic chemistry. Moreover, since Cu2+ is a redox-active ion, Cu2+-polymer
systems may also serve as oxidative catalysts for further investigation of
Cu-centered oxidation and oxygenation chemistry.
Acknowledgments
This research on hydrolytic chemistry of phosphoesters is partially supported
by the Petroleum Research Funds administrated by the American Chemical Society
(ACS-PRF #35313AC3). A.I.H acknowledges the Egyptian Government for a scholarship
to perform research overseas. Aswini Komarla, Anupama Kotha, Kara Brown and
Jane Zhu from the USF Summer Program for High School Students are acknowledged
for their contribution to the preliminary studies.
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