title: Probing the interactions between carboxylated multi-walled carbon nanotubes and copper-zinc superoxide dismutase at a molecular level.
abstract: In order to evaluate the toxicity of multi-walled carbon nanotubes (MWCNTs-COOH) at a molecular level, the effect of MWCNTs-COOH on antioxidant enzyme copper-zinc superoxide dismutase (Cu/ZnSOD) was investigated using fluorescence spectroscopy, UV/vis absorption spectroscopy, circular dichroism (CD) spectroscopy and isothermal titration calorimetry (ITC). By deducting the inner filter effect (IFE), the fluorescence emission spectra and synchronous fluorescence spectra indicated that there were interactions between MWCNTs-COOH and Cu/ZnSOD. Moreover, the microenvironment of the amino acid residues in the enzyme was changed slightly. The UV/vis absorption and CD spectroscopic results showed appreciable conformational changes in Cu/ZnSOD. However, the results of a Cu/ZnSOD activity determination did not show any significant difference. In other words, MWCNTs-COOH has no significant effect on enzyme activity. The ITC results showed that the binding of MWCNTs-COOH to Cu/ZnSOD was a weak endothermic process, indicating that the predominant force of the binding was hydrophobic interaction. Moreover, it was essential to consider the IFE in fluorescence assays, which might affect the accuracy and precision of the results. The above results are helpful in evaluating the oxidative stress induced by MWCNTs-COOH in vivo.
authors.affiliation: Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan, 250100, People's Republic of China.
authors.forename: Jin
authors.initials: J
authors.lastname: Guan
authors.affiliation: Shandong Institute for Food and Drug Control, Jinan, 250101, People's Republic of China.
authors.forename: Guiliang
authors.initials: G
authors.lastname: Liu
authors.affiliation: Shandong Environmental Monitoring Centre, Shandong, 250101, People's Republic of China.
authors.forename: Kai
authors.initials: K
authors.lastname: Cai
authors.affiliation: Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan, 250100, People's Republic of China.
authors.forename: Canzhu
authors.initials: C
authors.lastname: Gao
authors.affiliation: Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan, 250100, People's Republic of China.
authors.forename: Rutao
authors.initials: R
authors.lastname: Liu
mesh_terms: D002151:Calorimetry / Q000379:methods; D002942:Circular Dichroism; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000633:toxicity*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D037742:Nanotubes, Carbon; D013482:Superoxide Dismutase
keywords: Cu/ZnSOD; ITC; MWCNTs-COOH; activity inhibition; spectroscopy