title: Probing the toxic mechanism of Ag⁺ with lysozyme.
abstract: Silver (Ag) is widely used in human activities, which provides possibilities to distribute in organisms and tissues, resulting in harmful effects on human health. In this work, lysozyme was chosen as the target molecule to study the mechanism of toxic interactions between Ag(+) and protein using fluorescence emission spectra, synchronous fluorescence spectra, UV-vis absorption spectra, circular dichroism (CD) spectra, isothermal titration calorimetry (ITC), and enzyme activity assay. The results of fluorescence emission and synchronous fluorescence showed that there were interactions between Ag(+) and lysozyme by eliminating the inner filter effect (IFE). Data from UV-vis spectra indicated that the frame structure of lysozyme became looser with Ag(+) existent, while the micro-environment of aromatic amino acid residues did not show any significant alteration. CD results suggested that the secondary structure of lysozyme presented a decrease in α-helix contents with the increasing amount of Ag(+). ITC results showed Ag(+) can spontaneously bind with lysozyme through hydrogen bonding and van der Waals forces with one binding site (Ka=1.93×10(6)). The lysozyme activity was inhibited by Ag(+) according to the enzyme activity assay, revealing that Ag(+) bound to lysozyme at the active site which resulted in inhibition of lysozyme activity. This work showed that Ag(+) can cause damages to the structure and function of lysozyme.
authors.affiliation: School of Environmental Science and Engineering, China-America CRC for Environment & Health, Shandong Province, Shandong University, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Wu
authors.affiliation: School of Environmental Science and Engineering, China-America CRC for Environment & Health, Shandong Province, Shandong University, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: School of Environmental Science and Engineering, China-America CRC for Environment & Health, Shandong Province, Shandong University, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Sun
authors.affiliation: School of Environmental Science and Engineering, China-America CRC for Environment & Health, Shandong Province, Shandong University, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: School of Environmental Science and Engineering, China-America CRC for Environment & Health, Shandong Province, Shandong University, 27# Shanda South Road, Jinan 250100, PR China. Electronic address: rutaoliu@sdu.edu.cn.
authors.forename: Rutao
authors.initials: R
authors.lastname: Liu
mesh_terms: D000818:Animals; D001665:Binding Sites; D002645:Chickens; D002942:Circular Dichroism; D006801:Humans; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012834:Silver / Q000633:toxicity*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D012834:Silver; D009113:Muramidase
keywords: Ag(+); Circular dichroism spectra; Fluorescence spectra; Isothermal titration calorimetry; Lysozyme; UV–vis absorption spectra