title: Highly efficient conversion of superoxide to oxygen using hydrophilic carbon clusters.
abstract: Many diseases are associated with oxidative stress, which occurs when the production of reactive oxygen species (ROS) overwhelms the scavenging ability of an organism. Here, we evaluated the carbon nanoparticle antioxidant properties of poly(ethylene glycolated) hydrophilic carbon clusters (PEG-HCCs) by electron paramagnetic resonance (EPR) spectroscopy, oxygen electrode, and spectrophotometric assays. These carbon nanoparticles have 1 equivalent of stable radical and showed superoxide (O2 (•-)) dismutase-like properties yet were inert to nitric oxide (NO(•)) as well as peroxynitrite (ONOO(-)). Thus, PEG-HCCs can act as selective antioxidants that do not require regeneration by enzymes. Our steady-state kinetic assay using KO2 and direct freeze-trap EPR to follow its decay removed the rate-limiting substrate provision, thus enabling determination of the remarkable intrinsic turnover numbers of O2 (•-) to O2 by PEG-HCCs at >20,000 s(-1). The major products of this catalytic turnover are O2 and H2O2, making the PEG-HCCs a biomimetic superoxide dismutase.
authors: Department of Chemistry and.
authors: Errol L G
authors: EL
authors: Samuel
authors: Department of Chemistry and Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, TX 77005;
authors: Daniela C
authors: DC
authors: Marcano
authors: Hematology, Internal Medicine, University of Texas Houston Medical School, Houston, TX 77030;
authors: Vladimir
authors: V
authors: Berka
authors: Interdepartmental Program in Translational Biology and Molecular Medicine and Departments of Molecular Physiology and Biophysics and.
authors: Brittany R
authors: BR
authors: Bitner
authors: Hematology, Internal Medicine, University of Texas Houston Medical School, Houston, TX 77030;
authors: Gang
authors: G
authors: Wu
authors: Department of Chemistry and.
authors: Austin
authors: A
authors: Potter
authors: Neurology, Baylor College of Medicine, Houston, TX 77030; and Center for Translational Research in Inflammatory Diseases, Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030.
authors: Roderic H
authors: RH
authors: Fabian
authors: Interdepartmental Program in Translational Biology and Molecular Medicine and Departments of Molecular Physiology and Biophysics and.
authors: Robia G
authors: RG
authors: Pautler
authors: Interdepartmental Program in Translational Biology and Molecular Medicine and Neurology, Baylor College of Medicine, Houston, TX 77030; and Center for Translational Research in Inflammatory Diseases, Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030 tkent@bcm.edu Ah-Lim.Tsai@uth.tmc.edu tour@rice.edu.
authors: Thomas A
authors: TA
authors: Kent
authors: Hematology, Internal Medicine, University of Texas Houston Medical School, Houston, TX 77030; tkent@bcm.edu Ah-Lim.Tsai@uth.tmc.edu tour@rice.edu.
authors: Ah-Lim
authors: AL
authors: Tsai
authors: Department of Chemistry and Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, TX 77005; tkent@bcm.edu Ah-Lim.Tsai@uth.tmc.edu tour@rice.edu.
authors: James M
authors: JM
authors: Tour
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D017665:Hydroxyl Radical / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000737:chemistry*
chemical_list: D013481:Superoxides; D017665:Hydroxyl Radical; D011092:Polyethylene Glycols; D012972:Sodium Hydroxide; D002244:Carbon; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D010100:Oxygen
keywords: antioxidant; carbon nanoparticles; hydrophilic carbon clusters; superoxide; superoxide dismutase mimetic