Preparation And Properties Of Novel Immobilized Metal-ions Affinity Adsorbents

Immobilized metal-ions affinity (IMA) adsorbent is composed of three parts, which are support, chealtor and immobilized metal-ions. The adsorption of these adsorbents is based on specific interactions between proteins in solution and metal ions fixed to the solid support. A suitable support is a key point for protein adsorption. Many soft gels of polysaccharides have served as supports, with the quality of high biocompatibility and protein capacity. However, they also have some shortcomings such as severe shrinkage after drying or under pressure, and hydrolyzed in acidic or high temperature conditions. Silica gel as a rigid support has also been used, with disadvantages of chemical instability at pH values greater than 8.0, low protein capacity and strong non-specific adsorption. The modification of silica gel surface by polysaccharides combines the advantages of polysaccharides, in particular their hydrophilic features, with the mechanical resistance properties of silica support.β-Cyclodextrin (CD) is a cyclic oligosaccharide consisting of 7 glucose units linking throughα-1,4-glycosidic linkages. Cyclodextrins can form weak and non-covalent complexes with hydrophobic sites present in partially refolded protein intermediates to prevent aggregation, which have also proven effective for helping protein refolding. It may be an alternative to use cyclodextrins as IMA supports.In this work, two types of IMA adsorbent withβ-cyclodextrin bonded silica gel andβ-cyclodextrin polymer coated silica gel as the support were prepared by a three-step procedures, consisting of attachingβ-cyclodextrin on silica gel, coupling the ligand of iminodiacetic acid (IDA) and metal ions immobilization. The adsorption capability of adsorbent towards bovine serum albumin (BSA) andα-amylase was studied and the purification performance of the technical gradeα-amylase was also determined. The recovery ofα-amylase was 78.8 % with 15-fold specific activity enhanced and the adsorbent could be used repeatedly. The matrix-assisted refolding of urea denatured amylase was also studied.