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Idrogenasi

Idrogenasi. ______________________________________________________. Reverse Engineering of Hydrogenases Function. ______________________________________________________. Hydrogenases were discovered 80 years ago Three evolutionary distinct families

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Idrogenasi

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  1. Idrogenasi ______________________________________________________

  2. Reverse Engineering of HydrogenasesFunction ______________________________________________________ • Hydrogenases were discovered 80 years ago • Three evolutionary distinct families • TechnologicalRelevance (Energy carrier) • H2 oxidation vs H+ reduction (H2 2H+ + 2e-) • Magnuson A, Anderlund M, Johansson O, Lindblad P, Lomoth R, Polivka T, • Ott S, Stensjo K, Styring S, Sundstrom V, Hammarstrom L, Acc. Chem. Res. 2009, 42, 1899 • Lukey MJ, Parkin A, RoesslerMM, Murphy BJ, Harmer J, Palmer T, Sargent F, Armstrong FA,J. Biol. Chem. 2010, 285, 3928

  3. H2asenergycarrier (near -?- future)

  4. Renewableenergies • Renewableenergies are thoseenergyformsobtainedfrom: • - regenerablesources • - sourcesthat are notdepletable on human-timescales. • "renewableenergies“: sun, wind, hydro, wave, geothermal • “non-renewableenergies“: fossilfuels, coal, natural gas, uranium. Solarenergy (clean, cheap, abundant) Difficultto catch and “store” in suitableenergycarriers

  5. H2asenergycarrier (distant -?- future) • water electrolysisusingsolarenergy

  6. Biological production of H2

  7. Reverse Engineering of HydrogenasesStructure ______________________________________________________ Three evolutionary distinct families: • [NiFe]-hydrogenases Volbeda A, Charon M H, Piras C, Hatchikian E C, Frey M, Fontecilla_Camps J C, Nature, 1995, 373, 580

  8. Reverse Engineering of HydrogenasesStructure ______________________________________________________ Three evolutionary distinct families: • [FeFe]-hydrogenases • Peters J W, Lanzilotta W N, Lemon B J, Seefeldt L C, Science, 1998, 282, 1853 • Nicolet Y, Piras C, Legrand P, Hatchikian C E, Fontecilla-Camps J C, Structure, 1999, 7, 13

  9. Reverse Engineering of HydrogenasesStructure ______________________________________________________ Three evolutionary distinct families: • [Fe]-hydrogenases Shima, S., Pilak, O., Vogt, S., Schick, M., Stagni, M.S., Meyer-Klaucke, W., Warkentin, E., Thauer, R.K., Ermler, U. Science 2008, 321, 572

  10. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism • Hox and Hred are catalyticallyactivestates • the coordination site trans toµ-CO isvacant H+, H2 , CO • NicoletY, de Lacey A, Fernandez V, Hatchikian E, Fontecilla-Camps J, J. Am. Chem. Soc., 2001, 123, 1596 • Fan H, Hall M, J. Biol. Inorg. Chem., 2001, 6, 467 • Liu Z, Hu P,J. Am. Chem. Soc, 2002, 124, 5175 • Fan H,Hall M,J. Am. Chem. Soc, 2002, 124, 4006 • ZampellaG, Greco C, Fantucci P, De Gioia L, Inorg. Chem., 2006, 45, 4109

  11. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism Fe(I)Fe(I), Fe2(III)Fe2(II), in agreement with experimental data

  12. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism Strongly exoergonic

  13. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism Fe(II)Fe(II), Fe2(III)Fe2(II) m-hydride thermodynamically more stable also in the protein

  14. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism No H2formation on Fe(II)Fe(II)

  15. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism • Reduction would take place on Fe4S4, then protonation of dtma would trigger electron transfer from Fe4S4 to Fe2S2. 2 1

  16. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism m- and terminal- hydrides are almostisoenergetic

  17. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism H2 formation is spontaneous on an Fe(II)Fe(I) species

  18. Team and collaborations _______________________________________________________ • Luca Bertini • Maurizio Bruschi • PiercarloFantucci • Claudio Greco • Giuseppe Zampella • Tom Rauchfuss, Universityof Illinois at Urbana-Champaign, USA • UlfRyde, UniversityofLund, Sweden • Chris Pickett, Universityof East Anglia, UK • Jean Talarmin, Philippe Schollhammer, Université de Bretagne Occidentale, France • Markus Reiher, ETH Zurich, Switzerland

  19. [NiFe]-hydrogenases ______________________________________________________ • Redox state of metal ions • Structure of intermediate species • Electronic configuration of the Ni ion Lubitzet al.; Chem. Phys. Chem. 2010, 11, 1127 QC studies

  20. [FeFe]-hydrogenases ______________________________________________________ DeLaceyet al. Chem. Rev., 2007, 107, 4304 • Redox state of metal ions • Structure of intermediate species • Chemical nature of the chelating ligand QC studies

  21. Structure-functionrelationships ______________________________________________________ [NiFe] hydrogenases: catalytic mechanism H2bindingto Fe(II) H2cleavage on a Ni(III)Fe(II) form Fan, H.-J.; Hall, M. B. J. Biol. Inorg. Chem.2001, 6, 467   

  22. Structure-functionrelationships ______________________________________________________ [NiFe] hydrogenases: catalytic mechanism Fan, H.-J.; Hall, M. B. J. Biol. Inorg. Chem.2001, 6, 467   

  23. Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism BP-86/TZVP results ΔG path= 2.6 kcal/mol Δ G≠path= 1.0 - 3.0 kcal/mol • Liu Z, Hu P,J. Am. Chem. Soc, 2002, 124, 5175 • Fan H,Hall M,J. Am. Chem. Soc, 2002, 124, 4006; • ZampellaG, Greco C, Fantucci P, De Gioia L,Inorg. Chem., 2006, 45, 4109

  24. a Structure-functionrelationships ______________________________________________________ [FeFe] hydrogenases: catalytic mechanism BP-86/TZVP results ΔG path a = 18.3 kcal/mol Δ G≠path a = 22.6 kcal/mol Δ G path b = -3.3 kcal/mol Δ G≠path b = 8.9 kcal/mol Zampella G, Greco C, Fantucci P, De Gioia L, Inorg. Chem., 2006, 45, 4109

  25. Role of ligands on geometric features ______________________________________________________ • rotated vsunrotated structures Bruschi M., Fantucci P., De Gioia L. Inorg. Chem. 43, 3733 (2004)

  26. Isocyanides in [FeFe] hydrogenases? _____________________________________________________ • HOMO is localized on the [2Fe]Hsubcluster • LUMO is localized on the Fe4S4subcluster • HOMO–LUMO gap is small • Similar results are obtained for proximal CN protonation Hred

  27. Isocyanides in [FeFe] hydrogenases? _____________________________________________________ • LUMO is localized on the [2Fe]Hsubcluster • Relevance for H2 uptake • Similar results are obtained for proximal CN protonation Hox

  28. Isocyanides in [FeFe] hydrogenases? _____________________________________________________ Hox • LUMO is localized on the Fe4S4subcluster • unoccupied MOs on [2Fe]H are shifted to more positive energies.

  29. Protonationregiochemistry ______________________________________________________ Zampella G, Fantucci P, De Gioia L, J. Am. Chem. Soc. 2009, 131, 10909

  30. Protonation regiochemistry ______________________________________________________ a. The reaction product does not correspond to an energy minimum structure and evolves back to reactant (the FeFe complex + triflic acid).

  31. Protonation regiochemistry ______________________________________________________ a. The reaction product does not correspond to an energy minimum structure and evolves back to reactant (the FeFe complex + triflic acid).

  32. Rfree factor: it is an R factor calculated for a set of reflections(typically 5–10%) that is not used in the refinement ofthe structure. It is an objective quality criterion that isused to avoid overfitting of the model

  33. Structure-functionrelationships ______________________________________________________ Relative stabilityofmu- and terminal-hydrides The energy difference between m-H and t-H species is a function of the subclusterredox and protonation state. In particular, the energy gap decreases upon protonation of dtma and concomitant reduction of the binuclear cluster

  34. What’s next? ______________________________________________________

  35. Discutere H2 formation vs H2 cleavage???

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