Characterization of the interaction between carbon black and three important antioxidant proteins using multi spectroscopy and modeling simulations.

A major user of carbon black is the pigment and dyes industry, where carbon black is incorporated into paints, inks, printers, and plastics. However, little is known about the mechanism underlying the toxicity of carbon black to antioxidant proteins. Carbon black can cause oxidative stress to organisms after they invade into the body. Antioxidant proteins play a key role in keeping the organism from nanoparticle-induced oxidative damage and tend to bind with nanoparticles immediately after their invading into the biological environment, so it is meaningful to elucidate the toxicity of nanoparticles on the antioxidant proteins. In this study, the toxicity of carbon black (SB100) on three different antioxidant proteins (TF (transferrin), SOD (superoxide dismutase), and LYZ (lysozyme)) were investigated. The multi-spectra studies indicated that SB100 interacted with these three proteins and changed their structure in different ways. SB100 changed the microenvironment of fluorophores in SOD and LYZ by quenching the fluorescence spectra of the two enzymes, while changed that of TF by increasing the fluorescence intensity of TF. SB100 changed the secondary structure of these three proteins by decreasing the α-helix content of TF and increasing that of SOD and LYZ. Moreover, SB100 changed the hydrophobicity of the three proteins in different ways as well. And SOD exhibits a more severe activity inhibition than LYZ after exposed to SB100. In summary, SB100 caused different structural and functional changes to these three antioxidant enzymes.