title: Denaturation and aggregation of hen egg lysozyme in aqueous ethanol solution studied by dynamic light scattering.
abstract: We applied dynamic light scattering technique on the model system of hen egg lysozyme in salt-free aqueous ethanol solution to study the mechanism of denaturation and aggregation of protein. At low ethanol concentration [0-63% (v/v)], the fast relaxation mode was observed, which was caused by lysozyme molecules in the solution interacting with each other with strong repulsive electrostatic force. At 45 and 63% (v/v) ethanol, the slow relaxation mode was also observed, which showed translational diffusive nature, similar to that observed in salt-free polyelectrolyte solution. At 72 or 81% (v/v) ethanol, the slow mode disappeared, leaving only the fast mode. However, the mutual diffusion coefficients obtained from the fast mode at 72 and 81% (v/v) ethanol decreased by about one order of magnitude compared with those from the fast mode at 0-63% (v/v). The reported alcohol-induced conformational transformation of lysozyme molecules at >60% (v/v) ethanol from their native structure to an alpha-helix-rich structure might cause such drastic decrease in the mutual diffusion coefficients. At the highest ethanol concentration of 90% (v/v), the slow mode reappeared, and its relaxation rate was decreasing with elapsed time, which is possibly due to the growth of aggregates of lysozyme molecules. X-ray diffraction results suggested that the intermolecular beta-sheet formation caused the aggregation. Thus, our results indicated that the change in molecular structure of lysozyme closely relates to the diffusion of molecules and their aggregation.
authors.affiliation: Special Division for Human Life Technology, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda 563-8577, Japan. shinpei.tanaka@aist.go.jp
authors.forename: S
authors.initials: S
authors.lastname: Tanaka
authors.forename: Y
authors.initials: Y
authors.lastname: Oda
authors.forename: M
authors.initials: M
authors.lastname: Ataka
authors.forename: K
authors.initials: K
authors.lastname: Onuma
authors.forename: S
authors.initials: S
authors.lastname: Fujiwara
authors.forename: Y
authors.initials: Y
authors.lastname: Yonezawa
mesh_terms: D000818:Animals; D002645:Chickens; D004531:Eggs; D000431:Ethanol; D007700:Kinetics; D008027:Light; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry*; D011489:Protein Denaturation; D012542:Scattering, Radiation; D012996:Solutions; D013997:Time Factors
chemical_list: D012996:Solutions; D000431:Ethanol; D009113:Muramidase