Abstract
Enzymatic polymerization has been noted as a powerful method to precisely synthesize polymers with complicated structures, such as polysaccharides, which are not commonly prepared by conventional polymerization. Phosphorylase is one of the enzymes which have been used to practically synthesize well-defined polysaccharides. The phosphorylase-catalyzed enzymatic polymerization is conducted using α-d-glucose 1-phosphate as a monomer, and maltooligosaccharide as a primer, respectively, to obtain amylose. Amylose is known to form supramolecules owing to its helical conformation, that is, inclusion complex and double helix, in which the formation is depended on whether a guest molecule is present or not. In this paper, we would like to report the preparation of amylose-carboxymethyl cellulose (CMC) conjugated supramolecular networks, by the phosphorylase-catalyzed enzymatic polymerization, using maltoheptaose primer-grafted CMC. When the enzymatic polymerization was carried out using the graft copolymer, either in the presence or in the absence of a guest polymer poly (ε-caprolactone) (PCL), the enzymatically elongated amylose chains from the primers on the CMC main-chain formed double helixes or inclusion complexes, depending on the amounts of PCL, which acted as cross-linking points for the construction of network structures. Accordingly, the reaction mixtures totally turned into hydrogels, regardless of the structures of supramolecular cross-linking points.
Highlights
Enzyme-catalyzed reactions have been employed to precisely synthesize biological and bio-related polymeric molecules with regular structures, which are identified as a term of enzymatic polymerization because they strictly progress with controlled regio, stereo, and conformational arrangements [1,2,3,4]
We have found that when the phosphorylase-catalyzed enzymatic polymerization is conducted in the presence of guest polymers with suitable hydrophobicity such as poly(ε-caprolactone) (PCL, a hydrophobic polyester), and dispersed in aqueous polymerization solvents which have larger sizes than those of the common guest molecules, the enzymatically propagating amylose chain helically interacts with the polymers to produce amylose-polymer inclusion complexes [14,15]
In the previous publications related to the present study, we have briefly reported phosphorylase-catalyzed enzymatic polymerization using G7 -grafted carboxymethyl cellulose (CMC), which forms a hydrogel with cross-linking points from amylosic double helixes in the polymerization mixture [32,33]
Summary
Enzyme-catalyzed reactions have been employed to precisely synthesize biological and bio-related polymeric molecules with regular structures, which are identified as a term of enzymatic polymerization because they strictly progress with controlled regio-, stereo-, and conformational arrangements [1,2,3,4]. Polysaccharides are the representative molecules, which have been beneficially constructed according to such advantages of enzymatic catalysis [5,6,7]. They are comprising very complicated structures which are comprised of a variety of monosaccharide units, linked through specific types of glycosidic linkages, with highly controlled regio- and stereoarrangements. Repeating units, and synthesized by the phosphorylase-catalyzed enzymatic polymerization of the α-D-glucose 1-phospahte (G-1-P) monomer [6,7,8,9,10].
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