Copyright © 2015 American Scientific Publishers All rights reserved Printed in the United States of America Article Journal of Nanoscience and Nanotechnology Vol. 15, 1473–1479, 2015 www.aspbs.com/jnn Evaluation on the Toxic Effects of NanoAg to Catalase Bin Zhang 1 , Wenxin Zhai 2 , Rutao Liu 1 ∗ , Zehua Yu 1 , Hengmei Shen 1 , and Xinxin Hu 1 1 School of Environmental Science and Engineering, Shandong University, China–America CRC for Environment and Health, Shandong Province, Jinan 250100, P. R. China 2 School of Business, Tianjin University of Finance and Economics, Hexi District, Tianjin 300200, P. R. China Protein is the functional actor of life. Research on protein damage induced by nanomaterials may give insight into the toxicity mechanisms of nanoparticles. Studying nano silver over the impact of the structure and function of catalase (CAT) at the molecular level, is of great significance for a comprehensive evaluation of their toxic effects. The toxic effects of nanoAg on catalase were thor- oughly investigated using steady state and time resolved fluorescence quenching measurements, ultraviolet-visible absorption spectroscopy, resonance light scattering spectroscopy (RLS), circular dichroism spectroscopy (CD) and transmission electron microscopy (TEM). NanoAg could decrease the amount of alpha-helix and increase the beta sheet structure, leading to loose the skeleton struc- ture of catalase. The characteristic fluorescence of catalase was obviously quenched, which showed the exposal of internal hydrophobic amino acids enhanced, and its quenching type is dynamic quenching. The result of RLS and TEM showed that the distribution and size of nanoAg become more uniform and smaller after their interaction, resulting in a decrease of RLS intensity. NanoAg could make the activity of catalase rise. By changing the structure of catalase, nanoAg increases its enzymatic activity to a certain extent, breaking down its balance in vivo, thereby affecting the normal physiological activities. NanoAg has obvious toxic effects on catalase. This paper provided a new perspective and method for the toxic effects of nanoAg to biological macromolecules; provided basic data and reference gist for the hygienics and toxicology studies of nanoAg. It is conducive to the toxicity prevention and control work of nanoAg, promoting nano-technology applied to human production and living better. Keywords: NanoAg, Catalase, Spectroscopy Technology, Transmission Electron Microscopy, Enzyme Activity. 1. INTRODUCTION Nano-technology has tremendous potential applications in biology and medicine, including disease diagnosis, drug targeting transmission, and biological sensors. 1–3 Nano- silver (nanoAg) is developed into a new nano-material based on nano technology. 4 5 Because of its unique charac- teristics, nanoAg has a wide range of applications in detec- tion, printed electronics, disinfection and food storage. 6–8 Furthermore, NanoAg materials have a close relation- ship with modern pharmacology and medicine. 910 NanoAg has more qualitative bactericidal capacity and could over- come drug resistance. 11 12 All mentioned above results in the relevant staff and local environmental larger dose exposure. Humans have attached great attention to its environmental hazards caused by the gradually increasing ∗ Author to whom correspondence should be addressed. use of nanoAg. 1 13 NanoAg has its own unique physical and chemical properties, so its interaction with organisms is different from ordinary silver materials. 14 So far at home and abroad, the previous methods investigating the toxicity of nano-silver mainly focused on morphology, determina- tion of mitochondrial function, cell proliferation, enzyme activity and cytotoxic testing. The overall level of toxicity testing has also been reported. 15–17 However, there is a lack of research on the mechanism at the molecular level. 3 18 19 In order to ensure the positive development of nano-silver materials, and reduce its injury to the natural ecological system, especially human beings, there is an urgent need to do a comprehensive and in-depth study on the toxic effects of nano-silver. Catalase (CAT) is a tetramer of four polypeptide chains, each over 500 amino acids long. 20 It contains four por- phyrin heme (iron) groups that allow the enzyme to react with the hydrogen peroxide. The optimum pH for human J. Nanosci. Nanotechnol. 2015, Vol. 15, No. 2 1533-4880/2015/15/1473/007 doi:10.1166/jnn.2015.9042 1473