title: Physicochemical Changes of Few-Layer Graphene in Peroxidase-Catalyzed Reactions: Characterization and Potential Ecological Effects.
abstract: The environmental implications of graphene have received much attention, however, little is known about how graphene affects or may be affected by the enzymatic reactions that are critically involved in natural organic matter transformation processes. We conducted experiments to examine the role of few-layer graphene (FLG) in the reaction system of tetrabromobisphenol A (TBBPA) mediated by horseradish peroxidase (HRP). We found that TBBPA was transformed by HRP into two products that were likely formed from coupling of two TBBPA radicals via interaction of an oxygen atom on one radical and a propyl-substituted aromatic carbon atom on the other. Presence of FLG greatly increased the reaction rate by protecting HRP from inactivation. Direct reactions between TBBPA radicals and FLG were unequivocally evidenced using (14)C labeling and the characteristic photoelectron response of bromine contained in TBBPA. The thickness, size, and aggregation profile of FLG was modified by the reaction as shown by multiple characterization tools. Assessment using Daphnia magna revealed a substantial decrease in the bioaccumulation and toxicity of the FLG after being modified. The data provides the first evidence that FLG can be modified in HRP-mediated reactions and indicates that such modifications may have strong implications in its ecological effects.
authors.affiliation: †State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, P. R. China.
authors.forename: Kun
authors.initials: K
authors.lastname: Lu
authors.affiliation: ‡College of Agricultural and Environmental Sciences, Department of Crop and Soil Sciences, University of Georgia, Griffin, Georgia 30223, United States.
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Huang
authors.affiliation: §College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, P. R. China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: †State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, P. R. China.
authors.forename: Liang
authors.initials: L
authors.lastname: Mao
mesh_terms: D000818:Animals; D055162:Biocatalysis; D002250:Carbon Radioisotopes; D003621:Daphnia / Q000378:metabolism; D055669:Ecological and Environmental Phenomena; D006108:Graphite / Q000737:chemistry*; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D010084:Oxidation-Reduction; D056951:Photoelectron Spectroscopy; D011075:Polybrominated Biphenyls / Q000302:isolation & purification; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002250:Carbon Radioisotopes; D011075:Polybrominated Biphenyls; D006108:Graphite; D006735:Horseradish Peroxidase; C020806:tetrabromobisphenol A