Journal
CHEMOSPHERE
Volume 323, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2023.138199
Keywords
Microplastics; Catalase; Light irradiation; Spectroscopy; Binding interaction
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Microplastics (MPs) undergo aging in the environment, affecting their physicochemical properties and interactions with biomacromolecules. This study investigated the structural and functional changes of catalase (CAT) induced by virgin and aged PVC-MPs. Results showed that light irradiation aged the PVC-MPs, leading to surface roughness and the presence of holes and pits. Aged MPs had more binding sites than virgin MPs, and they quenched the fluorescence of CAT and interacted with tryptophane and tyrosine residues. The interaction of CAT with aged MPs caused structural changes and dispersion of CAT. However, MPs had no effects on the heme groups and activity of CAT. This study highlights the potential negative effects of MPs on antioxidant enzymes and provides insights into the interaction mechanisms between MPs and biomacromolecules.
Microplastics (MPs) undergo physical, chemical, and biological aging in the environment, leading to changes in their physicochemical properties, affecting migration characteristics and toxicity. Oxidative stress effects induced by MPs in vivo have been extensively studied, but the toxicity difference between virgin and aged MPs and the interactions between antioxidant enzymes and MPs in vitro have not been reported yet. This study investigated the structural and functional changes of catalase (CAT) induced by virgin and aged PVC-MPs. It was shown that light irradiation aged the PVC-MPs, and the aging mechanism was photooxidation, resulting in a rough surface and appearing holes and pits. Because of the changes in physicochemical properties, aged MPs had more binding sites than virgin MPs. Fluorescence and synchronous fluorescence spectra results suggested that MPs quenched the endogenous fluorescence of CAT and interacted with tryptophane and tyrosine residues. The virgin MPs had no significant effect on the skeleton of CAT, while the skeleton and the polypeptide chains of CAT became loosened and unfolded after binding with the aged MPs. Moreover, the interactions of CAT with virgin/aged MPs increased the alpha-helix and decreased the beta-sheet contents, destroyed the solvent shell, and resulted in a dispersion of CAT. Due to the large size, MPs cannot enter the interior of CAT and have no effects on the heme groups and activity of CAT. The interaction mechanism between MPs and CAT may be that MPs adsorb CAT to form the protein corona, and aged MPs had more binding sites. This study is the first comprehensive investigation of the effect of aging on the interaction between MPs and biomacromolecules and highlights the potential negative effects of MPs on antioxidant enzymes.
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