Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 112, Issue 8, Pages 2343-2348Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1417047112
Keywords
superoxide; antioxidant; carbon nanoparticles; hydrophilic carbon clusters; superoxide dismutase mimetic
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Funding
- Mission Connect Mild Traumatic Brain Injury Consortium [W81XWH-08-2-0141, W81XWH-08-2-0143]
- Alliance for NanoHealth Grant [W81XWH-090-2-0139]
- University of Texas Health Science Center through National Institutes of Health [HL095820, NS084290]
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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(center dot-)) dismutase-like properties yet were inert to nitric oxide (NO center dot-) 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(center dot-) to O-2 by PEG-HCCs at > 20,000 s(-1). The major products of this catalytic turnover are O-2 and H2O2, making the PEG-HCCs a biomimetic superoxide dismutase.
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