Adsorption and desorption of lysozyme on nano-sized magnetic particles and its conformational changes

Adsorption and desorption of lysozyme on nano-sized magnetic particles and its conformational change were studied in this work. Adsorption of lysozyme on nano-sized magnetic particles (Fe3O4) was carried out at different pH. Maximum adsorption of lysozyme(4.65 mg/m(2)) occurred at its isoelectric point (pI = 11.1). Differential scanning calorimetry (DSC) results show that the lysozyme adsorbed on magnetic particles did not show any thermal transition over the range 20-100degreesC. High desorption of lysozyme from magnetic particles was achieved using NaH2PO4 (pH4.0) (90%) and NaSCN (pH6.0) (97%) as desorbents. The conformational change of the lysozyme desorbed by NaH2PO4 was small, while the lysozyme desorbed by NaSCN underwent a significant conformational change as measured by the intrinsic fluorescence. Eighty-eight and 82% activity was retained in the desorbed enzyme for desorption by NaH2PO4 and NaSCN, respectively. (C) 2004 Elsevier B.V. All rights reserved.