Development of Artificial Enzymes by Surface Molecular Imprinting

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A molecular imprinting technique is one of the promising approaches to design "tailor-made" catalytic sites. However, it still has two fundamental drawbacks : difficulties to introduce water-soluble substrates as an imprinting molecule in the catalytic sites, and slow catalytic kinetics arising from the inner diffusion of substrates toward the catalytic sites formed deeply in the polymer matrix. To conquer these problems, we proposed a novel molecular imprinting technique for constructing recognition sites on the polymer surface called "surface molecular imprinting technique". An imprinted polymer was prepared by polymerizing water-in-oil (W/0) emulsions containing a functional host molecule, an imprint molecule and a cross-linking agent.In this study, we designed a novel functional host molecule possessing a high inter facial activity, considering that the host molecule should be located at water-oil interface to yield a high specific recognition. Furthermore we introduced an imidazole molecule as a functional group to catalyze the hydrolysis reaction of substrates. Using the newly synthesized functional host molecule, an enzyme-mimic polymer was prepared by imprinting a substrate analogue through the complex formation between a cobalt ion and the imidazole moiety. The catalytic properties of artificial biocatalysts were investigated on the hydrolysis reaction of an amino acid ester by comparing to control experiments. The enzyme-mimic biocatalyst showed a high activity and maintained high stability for a long time.