Bio-mimic Enzyme: Synthesis and Characterization of Cu(II)-Cu(II) and Cu(II)-Zn(II) Catalyst System Mimicking the Superoxide Dismutase
Date Issued
2011
Date
2011
Author(s)
Fang, Ya-Cheng
Abstract
Copper zinc superoxide dismutase (CuZnSOD) is an antioxidant metalloenzyme to catalyze the dismutation of superoxide anion radical (O2－․) into hydrogen peroxide and oxygen to reduce the steady-state concentration of O2－․. A series of imidazolate-bridged homo- and hetero- dinuclear Cu(II)-Cu(II) and Cu(II)-Zn(II) model compounds were synthesized and encapsulated into various mesoporous silica/aluminosilicates (MPS/Al-MPS) to mimic the structure and functionalities of CuZnSOD enzyme. Inspired by the local environments of guanidinium group in the native CuZnSOD enzyme in facilitating the superoxide dismutation, we carefully modified the silanol surface of MPS with N-trimethoxysilylpropyl-N,N,N-trimethyl-ammonium chloride (TMAC) to prepare MPS-N+ to yield the needed local environment for the active site of model compounds and to facilitate the disproportionation of O2－․. We employed the following spectroscopic techniques: UV-Vis, EPR and EXAFS to characterize the active site-Cu(II) ion of the immobilized mimic complexes, and to obtain the structural information of Cu(II) and Zn(II) centers confined in MPSs. The O2－․ disproportionation activity of mimic complexes was measured by nitro blue tetrazolium (NBT) assay. The encapsulated complexes yielded good stability against hydrothermal treatment and enhanced the O2－․ disproportionation activity in various MPS solids. The spectroscopic studies further allow us to establish the structure-reactivity relationship between the nanostructure of MPS and the efficacy of the superoxide dismutation in MPS, and to elucidate the mechanism of the SOD-like activity of immobilized model compounds in MPS. Furthermore, we utilized the oxidative damage model of HeLa cells to study the protective effect of mimic materials in the presence of paraquat (PQ) oxidant.
Subjects
nanotechnology
mesoporous materials
mimic enzyme
CuZnSOD
cell protection
Type
thesis
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