OK, so you’ve made the Ru complexes. - PowerPoint PPT Presentation

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OK, so you’ve made the Ru complexes.

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  1. OK, so you’ve made the Ru complexes. Now, how are you going to determine what it does with DNA? Will your complex bind DNA, like this? Will the other complexes also bind DNA? Will your complex cleave (damage) DNA? Will the other complexes cleave DNA?

  2. How might their different structures affect their behavior with DNA? • Electronic Spectroscopy (UV/vis) • Cyclic Voltammetry (Ered)

  3. Electronic Spectroscopy The Ru complexes are all orange: Won’t their UV/vis spectra be the same?

  4. Cyclic Voltammetry A Method to Measure Electrochemical Behavior and Ered • Will the complexes have different Ru redox potentials?

  5. The Same Question will be asked of your hemes: Can changing Heme substituents vary Fe(3+/2+) reduction potentials?

  6. The Cyclic Voltammetry Experiment

  7. +current, cathodic ic + potential, V -potential, V -current, anodic ia

  8. +current, cathodic ic Reduction + potential, V -potential, V Oxidation -current, anodic ia

  9. +current, cathodic ic When no electroactive species is present, no current flows, no ic nor ia This is what background electrolyte should look like. + V -V +1.0 V -1.0 V -current, anodic ia

  10. +current, cathodic ic Starting at a + V, Initially no current flows + V -V +1.0 V -1.0 V -current, anodic ia

  11. +current, cathodic ic If a reducible species is present ic will increase + V -V +1.0 V -1.0 V -current, anodic ia

  12. +current, cathodic ic And continue to increase + V -V +1.0 V -1.0 V -current, anodic ia

  13. Until all of the species is reduced. ic has reached a maximum. +current, cathodic ic + V -V +1.0 V -1.0 V -current, anodic ia

  14. +current, cathodic ic Then ic decreases until… + V -V +1.0 V -1.0 V -current, anodic ia

  15. +current, cathodic ic It again reaches the background current level. + V -V +1.0 V -1.0 V -current, anodic ia

  16. +current, cathodic ic Now the potential is reversed + V -V +1.0 V -1.0 V -current, anodic ia

  17. +current, cathodic ic And as V is more positive, the reduced species can be re-oxidized + V -V +1.0 V -1.0 V -current, anodic ia

  18. +current, cathodic ic So ia decreases to a maximum + V -V +1.0 V -1.0 V -current, anodic ia

  19. +current, cathodic ic Where all has been oxidized, + V -V +1.0 V -1.0 V -current, anodic ia

  20. +current, cathodic ic Then ia decreases, back to the background level. + V -V +1.0 V -1.0 V -current, anodic ia

  21. +current, cathodic ic Important features: Ec + V -V +1.0 V -1.0 V -current, anodic ia Ea

  22. +current, cathodic ic Ec E1/2is ~ EoRed E1/2 + V -V +1.0 V -1.0 V -current, anodic ia Ea

  23. +current, cathodic ic Using an Fe(3+) heme, Fe is electroactive, (and also the heme!) … All Fe(3+) + V -V +1.0 V -1.0 V -current, anodic ia

  24. +current, cathodic ic A little Fe(2+) formed + V -V +1.0 V -1.0 V -current, anodic ia

  25. +current, cathodic ic more Fe(2+) formed + V -V +1.0 V -1.0 V -current, anodic ia

  26. +current, cathodic ic Largest cathodic current, Max rate of Fe(2+) formed + V -V +1.0 V -1.0 V -current, anodic ia

  27. +current, cathodic ic Little Fe(3+) left; Less Fe(2+) forms; Decrease in ic + V -V +1.0 V -1.0 V -current, anodic ia

  28. +current, cathodic ic all Fe(2+) now + V -V +1.0 V -1.0 V -current, anodic ia

  29. +current, cathodic ic + V -V +1.0 V -1.0 V -current, anodic ia

  30. +current, cathodic ic + V -V A little Fe(2+) is re-oxidized to Fe(3+) +1.0 V -1.0 V -current, anodic ia

  31. +current, cathodic ic + V -V +1.0 V -1.0 V -current, anodic ia

  32. +current, cathodic ic + V -V +1.0 V -1.0 V Nearly all Fe(2+) has been oxized -current, anodic ia

  33. +current, cathodic ic + V -V +1.0 V -1.0 V All back to Fe(3+). Cycle could be run again, many times. -current, anodic ia

  34. +current, cathodic ic Important features: Ec + V -V +1.0 V -1.0 V -current, anodic ia Ea

  35. +current, cathodic ic Ec E1/2 for Fe(3+/2+) reduction E1/2 + V -V +1.0 V -1.0 V -current, anodic ia Ea

  36. the black box Working Electrode: Where the redox reaction action occurs

  37. the black box Working Electrode: Where the redox reaction action occurs Reference Electrode: Defines “0” potential for the cell. We use Ag/AgCl

  38. the black box Working Electrode: Where the redox reaction action occurs Auxilliary Electrode: Needed to complete circuit. We use a Pt wire Reference Electrode:

  39. the black box Working Electrode: Where the redox reaction action occurs Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) At start of CV experiment…

  40. the black box Working Electrode: Where the redox reaction action occurs Fe(2+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Moving up the cathodic current peak…

  41. the black box Working Electrode: Where the redox reaction action occurs Fe(2+) Fe(3+) Fe(3+) Fe(3+) Fe(2+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Still moving up the cathodic current peak…

  42. the black box Working Electrode: Where the redox reaction action occurs Fe(2+) Fe(2+) Fe(3+) Fe(3+) Fe(2+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) After the maximum cathodic current peak…

  43. the black box Working Electrode: Where the redox reaction action occurs Fe(2+) Fe(3+) Fe(3+) Fe(3+) Fe(2+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Moving down the anodic current peak…

  44. the black box Working Electrode: Where the redox reaction action occurs Fe(2+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Sill moving down the anodic current peak…

  45. the black box Working Electrode: Where the redox reaction action occurs Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) Fe(3+) At end of CV experiment…

  46. In your CV scans of Fe(porphyrin)Cl, you will see: +ic -V + V Interpretation???? -ia

  47. One more thing: Use of internal reference, ferrocene +ic -V + V E(1/2) values of sample are reported vs. ferrocene (example….) -ia

  48. Schedule for Thursday Nov. 1 Calculate E(1/2) for your data immediately, both vs. reference and corrected, vs. ferrocene After that: 3:30 Everyone meet in 264 to discuss results 4:15 – Attend Seminar by Dr. Nathanial Nucci

  49. How is the range of Heme Potentials in Respiration adjusted?