title: Effects of metal oxide nanoparticles on the structure and activity of lysozyme.
abstract: We investigated the effects of nanoparticles (NPs) on the structure and activity of hen egg-white lysozyme (HEWL) using CeO2and ZnO NPs. Our results showed that CeO2NPs triggered the transition of lysozyme secondary structure from α-helix to β-sheet. CeO2NPs also induced the hydrophobic region of lysozyme to become exposed to the solvent. In contrast, the secondary structure content and hydrophobic region of lysozyme were only slightly changed in the case of ZnO NPs. In addition, the activity of the lysozyme was observed to decrease upon adsorption on CeO2NPs, whereas the effect of ZnO NPs on activity was negligible. The glutaraldehyde crosslinking results indicated that the percentage of the dimeric form of lysozyme was greatly enhanced by the addition of both NPs. Furthermore, the adsorption capacity, degree of favorability of adsorption, and surface heterogeneity for CeO2NPs were found to be greater than those on ZnO NPs. Given that CeO2NPs exhibit a higher surface area/mass than ZnO NPs, the surface concentration of lysozyme on CeO2NPs was lower than that on ZnO NPs. This result suggested that more direct interactions were involved between CeO2NPs and lysozyme, thereby leading to a more significant effect. Moreover, higher surface curvatures may also cause destruction of lysozyme's structure and thus affect its activity. In addition, taking into account the surface properties and protein properties, the Toth adsorption model along with the generated site energy distribution was further used to exaplain the difference between the results (e.g., structure, stability, and activity) of lysozyme adsorption on CeO2and ZnO NPs. The results reported here may aid in better understanding the beneficial or harmful impacts of nanoparticles on the biological systems.
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Cheng
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Chia-Min
authors.initials: CM
authors.lastname: Lai
authors.affiliation: Department of Chemical Engineering and Materials Science/Environmental Technology Research Centre, Yuan Ze University, No.135, Yuandong Rd., Zhongli Dist., Taoyuan City 320, Taiwan. Electronic address: kslin@saturn.yzu.edu.tw.
authors.forename: Kuen-Song
authors.initials: KS
authors.lastname: Lin
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan. Electronic address: sswang@ntu.edu.tw.
authors.forename: Steven S-S
authors.initials: SS
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D000818:Animals; D001665:Binding Sites; D002563:Cerium / Q000737:chemistry*; D002645:Chickens; D002942:Circular Dichroism; D003432:Cross-Linking Reagents / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005976:Glutaral / Q000737:chemistry; D007526:Isoelectric Point; D053768:Metal Nanoparticles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009113:Muramidase / Q000737:chemistry*; D020033:Protein Isoforms / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D020033:Protein Isoforms; D012997:Solvents; D002563:Cerium; C030583:ceric oxide; C421864:hen egg lysozyme; D009113:Muramidase; D015034:Zinc Oxide; D005976:Glutaral
keywords: Activity; Adsorption isotherm; Cerium oxide; Lysozyme; Nanoparticle; Structure; Zinc oxide