Adsorption, desorption, and conformational changes of lysozyme from thermosensitive nanomagnetic particles

Adsorption of globular protein, lysozyme, on thermosensitive poly (N-isopropyl acrylamide) coated nanomagnetic particles was studied at different temperatures and pHs. It was observed that a maximum amount of lysozyme was adsorbed at a temperature above the lower critical solution temperature (LCST) (32 degrees C) of the polymer and at the isoelectric point (p(I) = 11) of lysozyme. Desorption was carried out using either NaH2PO4 (pH 4) or NaSCN (pH 6) as the desorbing agents. Conformational changes in lysozyme on desorption from nanomagnetic particles was studied by circular dichroism and intrinsic fluorescence spectroscopy. Lysozyme desorbed by NaH2PO4 showed very little conformational changes while lysozyme desorbed by NaSCN showed significant conformational changes, and 87% enzymatic activity was retained in the desorbed enzyme for desorption by NaH2PO4. (C) 2007 Elsevier Inc. All rights reserved.