Exploring the toxic effects and mechanism of lead-loaded ultrafine carbon black on lysozyme

As an important part of atmospheric ultrafine particles (UFPs), the safety evaluation of ultrafine carbon black (UFCB) has been a hot topic of discussion among researchers. In this work, we studied and compared the interaction of ultrafine carbon black (P35) with lysozyme before and after lead loading and their effects on protein structure. Scanning electron microscope, Zeta potential, Fourier transform infrared spectroscopy and particle size analysis were used to characterize the surface characteristics, dispersion, and particle size distribution of UFCB after ozone modification. Steady-state fluorescence spectroscopy, synchronous fluorescence spectroscopy, ultraviolet spectrophotometry and circular dichroism were used to evaluate the effect of UFCB on the structure of lysozyme before and after lead loading. The results showed that the hydrophobicity of protein amino acids before and after lead loading both showed a weakening trend, but after the adsorption of lead, the secondary structure stability of lysozyme is lower than that before lead loading. The results of the enzyme activity assay showed that the lead-loaded ultrafine carbon black (UFCB-Pb) caused a significant decrease in lysozyme activity compared to the change in the absence of lead. This study, therefore, provides fundamental information on the toxic effects of lead-loaded ultrafine carbon black on proteins, and offers beneficial idea for exploring the combined pollution of ultrafine particles. (C) 2020 Elsevier B.V. All rights reserved.