Effect of graphene oxide on conformation and activity of catalase

To explore the biocompatibility of graphene oxide (GO) with proteins, we investigated its effects on conformation and activity of catalase, by using molecular spectroscopic techniques such as UV-visible absorption, fluorescence, circular dichorism (CD) and fourier transform infrared (FT-IR) spectroscopy, and conducting in vitro enzymatic activity assay. CD combined with FT-IR and UV-visible spectra measurements indicated that GO induced the decrease of a-helical content and the increase of beta-sheet structure in catalase, resulting in the loosening and unfolding of the protein skeleton. The internal hydrophobic amino acids (mainly tryptophan) in the protein were exposed, and their characteristic fluorescence was distinctly quenched, according to synchronous fluorescence and fluorescence emission together with UV-visible spectra analyses. The results showed that the tertiary and secondary structure of catalase is changed by GO. The conformational changes of the protein were also found to show a dependence on concentration and time of GO treatment. Moreover, the activity assay indicated that catalase activity is inhibited by GO. The study demonstrated that GO could cause negative effects on proteins, and the biosafety of its application may worth further investigation. (C) 2013 Elsevier Ltd. All rights reserved.