14/4/2010
Abstract
In the present study, the copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were synthesized by gamma radiation induced radical polymerization, in order to examine the potential use of these hydrogels in immobilization
of Citrullus vulgarisurease. Gelation and Swelling properties of PHEMA and copolymeric P (HEMA/IA) hydrogels with different IA contents (96.5/3.5, 94.4/5.6 and 92.5/7.5 mol) were studied in a wide pH range. Initial studies of so-prepared hydrogels show interesting pH sensitivity in swelling and immobilization. C. vulgarisurease was immobilized on HEMA/IA (92.5/7.5) at 6 kGy with 41.3% retention of activity. The properties of free and immobilized urease were compared. Immobilized urease maintained a higher relative activity than free urease at both lower and higher pH levels, indicating that the immobilized urease was less sensitive to pH changes than the free urease. The Km value of the immobilized urease was approximately 2 times higher than that of the free urease. Temperature stability was improved for immobilized enzyme. The free formexhibited a loss about 80% of activity upon incubation for 15 min at 80?C. The influence of various heavy metal ions at the concentration of l mM was improved after enzyme immobilization. The immobilization of C. vulgarisurease on HEMA/IA (92.5/7.5) at 6 kGy showed a residual activity of 47 % after 4 reuses.
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