The complexes of lysozyme with poly(isobutylene-alt-maleic acid) (PIMA) and poly(1-tetradecene-alt-maleic acid) (PTMA) at pH 7.4 were characterized using static and dynamic light scattering. The electrostatic interaction of PIMA with lysozyme results in a loose complex structure, while the electrostatic and hydrophobic interactions between PTMA and lysozyme produce a compact complex structure. Lysozyme in PIMA complex particles remains a part of activity and structure analyzed by circular dichroism and substrate hydrolysis. However, lysozyme loses its tertiary structure and activity completely in PTMA complex. NaCl is more effective to dissociate PIMA-lysozyme complex by screening the electrostatic interaction, whereas GdHCl is more effective to dissociate PTMA-lysozyme complex by forming GdHCl-PTMA precipitates through extra hydrophobic interactions. In the release process, the denatured lysozyme molecules are able to avoid hydrophobic aggregation and fully regenerate their native structure and activity. (C) 2008 Wiley Periodicals, Inc.