Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 1 Iron Chelation in Biology Alvin L. Crumbliss Department of Chemistry Duke University Box Durham, NC Telephone: (919) Fax: (919) Website: Virtual Free Radical School

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 2 Iron Chelation in Biology Tutorial Guide Introduction: Biological Iron Coordination Chemistry Panels 3, 4 & 5 Common Iron Ligands in Biology Panel 8 Chelate Stability Definitions Panel 9 Iron Chelation and Transport Panels 14, 15 &16 Chelation and Redox Control Panels 10, 11 & 12 Influence of pH on Chelate Stability Panel 17 Influence of Chelate Stability on E 0 Panel 18 Influence of Chelation on Kinetics Panel 19 Chelation and Solubility Panel 6 Chelation and Redox Potential Panel 7 Oxidation State Influence on Chelate Stability Panel 13

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 3Introduction: Biological Iron Coordination Chemistry 1 st coordination shell; immediate chemical environment Common oxidation states: +2, +3 Common coordination numbers: 4, 5, 6 3 References [1,2]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 4 Introduction: Biological Iron Coordination Chemistry 4 References [1,2]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 5 The first coordination shell Prevents hydrolysis/precipitation Influences molecular recognition Controls redox potential Controls mobility Introduction: Biological Iron Coordination Chemistry 5

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 6 Fe insoluble due to hydrolysis Iron Chelation and Solubility Strong chelators prevent hydrolysis and precipitation 6

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 7 Iron Chelation and Redox Potential Fe(III/II) redox potential varies significantly with ligands in 1 st coordination shell 7 e.g. Desferal

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 8 Common Iron Ligands in Biology (I) (II) (III) (IV) (V) (VI) (VII)(VIII) (IX) 8

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 9 Iron Chelate Stability Definitions 9 References [3,4,5,6]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 10 Iron Chelation and Redox Control Why is it important? 10 Reference [6]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 11 Iron Chelation and Redox Control Why is it important? 11 Reference [6]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 12 Iron Chelation and Redox Control Why control E 0 ? 12 Reference [6]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 13 Thermodynamics Oxidation State Influence on Chelate Stability Kinetics Fe(OH 2 ) *OH 2 Fe(OH 2 ) 5 (*OH 2 ) 3+ + OH 2 Fe(OH 2 ) *OH 2 Fe(OH 2 ) 5 (*OH 2 ) 2+ + OH 2 -e - +e - t 1/2 = 4 ms t 1/2 = 0.2 s 13 References [7,8,9,10,11]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 14 Iron Chelation and Transport Reference [7] 14

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 15 Iron Chelation and Transport 15 References [4,5,6]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 16 Iron Chelation and Transport enterobactin Fe(III)-enterobactin complex 110 = ; pFe = 35.5 desferrioxamine B ferrioxamine B complex 110 = ; pFe = References [4,5,6]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 17 Influence of pH on Fe(III)-Chelate Stability (I) (II) 17 Reference [9,12]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 18 Influence of Fe(III)-Chelate Stability on E 0 18 References [6,10,13,14]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 19 Influence of Fe(III)-Chelation on Kinetics k 1 = 1.8 M -1 s -1 k 2 = 8.1 x 10 2 M -1 s Reference [5,15]

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 20 References 20

Iron in Biology Society For Free Radical Biology and Medicine Crumbliss 21 References 21 Acknowledgements