Magnetic bead cellulose particles and magnetic poly(HEMA–co–EDMA) microspheres with immobilized DNase I were
used for degradation of chromosomal and plasmid DNAs. Magnetic bead particles were prepared from viscose and magnetite
powder. Magnetic poly(HEMA–co–EDMA) microspheres were prepared by dispersion copolymerization of 2-hydroxyethyl
21 21 21 21 methacrylate and ethylene dimethacrylate in the presence of magnetite. Divalent cations (Mg , Ca , Mn and Co )
were used for the activation of DNase I. A comparison of free and immobilized enzyme (magnetic bead particles) activities
was carried out in dependence on pH and activating cation. The maximum of the activity of immobilized DNase I was
shifted to lower pH compared with free DNase I. DNase I immobilized on magnetic bead cellulose was used 20 times in the
degradation of chromosomal DNA. Its residual activity was influenced by the nature of activating divalent cation. The
21 immobilized enzyme with decreased activity was reactivated by Co ions. Ó 2002 Elsevier Science B.V. All rights
reserved.