The aggregation interaction between non-reducing-denatured egg white lysozyme during the refolding procedure in urea solution was studied by means of normal SDS-PAGE, cathode PAGE and size-exclusion chromatography. It was found that contrary to the refolding procedure of reduced-denatured egg white lysozyme in urea solution, no aggregate precipitate was formed in the refolding procedure of non-reducing-denatured egg white lysozyme in urea solution. When the final egg white lysozyme concentration in renaturation solution was lower than 4.0 mg/mL, no egg white lysozyme aggregate was formed during the refolding procedure of non-reducing-denatured egg white lysozyme in urea solution; when the final egg white lysozyme concentration was in the range of 4.0～8.0 mg/mL, the bi-molecular and tri-molecular egg white lysozyme aggregates could be formed through the non-covalent interaction among the egg white lysozyme intermediates formed in the refolding procedure of non-reducing-denatured egg white lysozyme; and when the final egg white lysozyme concentration was higher than 8.0 mg/mL, the tetra-molecular egg white lysozyme aggregate could also be formed besides the bi-molecular and tri-molecular egg white lysozyme aggregates. And finally, a suggested refolding procedure of non-reducing-denatured egg white lysozyme in urea solution was presented.

Key words: non-reducing-denatured egg white lysozyme, aggregation interaction, dilution renaturation, urea solution