LECTURE-3 - Lecture Outline Free Radical and Antioxidants...

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Free Radical and Antioxidants Lecture 3 Lecture Outline • Free Radical Chemistry • Antioxidant’s action • Repair mechanisms • Little bit of aging ….here and there Question? • Where are radicals produced ?
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MITOCHONDRIA RESPIRATION 4H + + O 2 2H 2 O (~95% of the time) O 2 *O 2 •- H 2 O 2 *Only 1-5% generate free radicals Reactive Oxygen Species • Approximately 1-5% of oxygen consumed by cells is reduced to the superoxide anion (O 2 - ) and hydrogen peroxide (H 2 O 2 ) •H 2 O 2 permeates cellular membranes, entering nearly all cellular compartments What is the oxidants production in a day? In theory by B. Halliwell • Using 3.5ml O 2 /kg/min gives at Rest •O 2 consumption of 352.8L/day (70kg; male) • 14.7 moles oxygen a day • If 1% of oxygen becomes a superoxide radical • 0.147 moles of superoxide is produced.
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White blood cells use myeloperoxidase to kill invading microbes O 2 Oxygen O 2 Superoxide H 2 O 2 Hydrogen peroxide HOX Hypohalous Acid NADPH Oxidase Peroxidase Cl - , Br - , I - , or SCN - Phagocyte-generated Oxidants Implicated in Host Defense and Inflammatory Disease Molecular Markers Reactive Aldehydes Myeloperoxidase Tyrosyl Chlorotyrosine Protein Dityrosine Lipid Peroxidation Nitrotyrosine HOCl ONOOH NO H 2 O 2 O 2 • – O 2 Cl 2 NO 2 NO 2 Lipid Peroxidation O 2 • – O 2 iNOS Endothelium eNOS NOX Podrez et al (2002) J. Biol. Chem . 277:38503-16 Podrez et al (2002) J. Biol. Chem . 277:38517-23 Monocytes Use MPO–generated NO- derived Oxidants to Convert LDL into an Atherogenic Form
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Peroxynitrite •O 2 - reacts extremely rapidly with NO to form Peroxynitrite ( ONOO - ) O 2 - + NO ONOO - • This is a non-radical species that is a potent oxidizing and nitrating intermediate. NO reacts very rapidly with the free O 2 •- to form ONOO - . N=O + O-O: - O=N-O-O: - .. .. .. .. .. .. .. .. .. . . . . . . .. .. .. .. . . . . .. .. .. .. “Radical” Reactions O 2 + e <=> O 2 - Equation 1 O 2 + 2e + 2H + H 2 O 2 Equation 2 O 2 - + O 2 - + 2H + SOD H 2 O 2 + O 2 Equation 3 H 2 O 2 + 2GSH GPX H 2 O + GSSG + ROH Equation 4 2H 2 O 2 + Catalase 2H 2 O + O 2 Equation 5 O 2 - + NO ONOO - Equation 6 O 2 - +M n+ O 2 + M (n-1)+ Equation 7 Fe 2+ + H 2 O 2 HO + HO - + Fe 3+ Equation 8 Hydroxyl Radical First YOU need REDOX active Iron First YOU need REDOX active Iron Fe Fe 3 + O 2 - Fe 2+ (Free or low molecular weight chelates of transition metals such as Fe 3+ are reduced by O 2 - to Fe 2+ ) Hydroxyl radical Continue • The Haber-Weiss reaction (also known as superoxide-driven Fenton chemistry).
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LECTURE-3 - Lecture Outline Free Radical and Antioxidants...

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