Lengths, Energies and Time Scales in Photosynthesis. Implications for Artificial Systems.

1. Lengths, Energies and Time Scales in Photosynthesis.Implications for Artificial Systems. • Dror Noy • Plant Sciences Dept. • Weizmann Institute of Science • Rehovot, Israel

2. How does Nature exploits fundamental physical principles in the construction of biological energy conversion systems?

3. How can we implement the Natural strategies in man-made energy conversion systems?

4. Carbon fixation Oxygenic Photosynthesis The best characterized Natural energy conversion scheme Photosystem II We focus on the primary photosynthetic reactions because these are by-far the best characterized and probably the best understood biological energy conversion processes

5. Oxygenic Photosynthesis The best characterized Natural energy conversion scheme Temporal Resolution < 0.1 ps Spatial Resolution: 2-3 Å

6. NADP+ 2H+ 2 x 2H+ 2H+ NADPH H+ The fundamental processes Chemical transformation Light driven Proton pumping Electron transfer (Tunneling, Diffusion) We focus on the primary photosynthetic reactions because these are by-far the best characterized and probably the best understood biological energy conversion processes

7. A simpler view • Energy and electron transfer rates between functional elements should be fast enough to: • Support the catalytic turnover rates • Exceed the rates of inherent relaxation processes and back-reactions PSII B6F PSI • Each transfer rate has a distinctive dependence ondistance, and energy. Cartoon by Richard Walker, from “Energy Plants & Man” by David Walker

8. Time (Rates), Length, and Energy Scales Membrane Potential 0.1 - 0.01 s-1

9. Length and Energy Scales of Light Absorption • Given an incoming photon flux, the absorption cross-sections defines a length scale • The driving force of the redox reactions define an energy scale by limiting the number of useful photons

10. A typical organic chromophore can support up to 5 catalytic cycles/second

11. Pigment Composition of Photosynthtetic Enzymes

12. Electron Transfer ∝ 10^(-0.6r-3.1⋅(ΔG+λ)2/λ) Energy Transfer ∝ (ro/r)6 Different distance and energy dependence for electron and energy transfer Electron tunneling Energy transfer Membrane Potential 0.1 - 0.01 s-1

13. Heliobacteria Green Sulfur Bacteria Purple Bacteria PSII PSI Side view Implications for the “natural leaf”

14. In photosystems, natural selection favors robust design with the predominant parameter being control over cofactor distances The basic physics of the transfer processes allow for a large degree of tolerance Conclusions

15. However...

16. 360 ps 180 ns 10.6 Å 160 μs Energy transfer 10 ps 15.5 Å 6.1 Å Implications for the “artificial leaf” ΔG = -0.35 eV λ = 0.7 eV 31 Å Distances must be controlled with sub nanometric accuracy

17. Concentration Quenching LHI-RC PSII LHCI- PSI PSI

18. Chlorophyll Proteins LH1 LH2 PSI PSI FMO LHC2 PSII

19. Rudimentary structures Iterative design High resolution structural information, only a bonus Non-natural Systems

20. De Novo Designed Protein Building Blocksfor Energy and Electron Transfer Relays

21. Hybrid Modular Design

22. De Novo Design of a Non-Natural Fold for an Iron-Sulfur Protein

23. Iron-Sulfur Clusters Proteins Complex I Bacterial Ferredoxin PSI Complex II Fe2 Hydrogenase NiFe Hydrogenase

24. Incorporating an Iron-Sulfur Cluster Center into the Hydrophobic Core of a Coiled Coil Protein Grzyb et al. BBA-Bioenergetics 1797 (2010) pp. 406-413

25. CCIS1:Coiled Coil Iron Sulfur Protein I CCIS1 All C->S Grzyb et al. BBA-Bioenergetics 1797 (2010) pp. 406-413

26. CCIS-Fdx Ferredoxin Loop Interface to CCIS CCIS1

27. De Novo Design of a Water Soluble Analog of Transmembranal Chlorophyll Proteins

28. Chlorophyll Proteins LH1 LH2 PSI PSI FMO LHC2 PSII

29. PSI PSI PSII Multi-Chl Protein by Redesign of a Common Natural Motif

30. Converting a Transmembranal Motif into a Water-Soluble Protein Step 1: Identify External Residues Step 2: Build Connecting Loop Step 3: Replace Hydrophobic Residues with Hydrophylic Ones

31. H H Water-Soluble BChls Bacteriochlorophyll a 132-OH- Bacteriochlorophyll a Mg Zn 132-OH- Bacteriopheophorbide a HO H 132-OH-Zn-Bacteriochlorophyllide a Phytyl HO ZnBChlide

32. PS3H2:PhotoSystem 3Helix Protein 2 Dimers Monomers PS3H2

33. PS3H2:PhotoSystem 3Helix Protein 2 PS3H2 PS3H2 H62A

34. Conclusions • Two examples of designing de novo protein cofactor complexes were presented: • An iron-sulfur cluster with a non-natural fold • A multi-Chl binding protein that is a water-soluble analog of a highly conserved transmembranal Chl-binding motif • These examples demonstrate: • The viability of protein de novo design for making novel functional proteins • The effectivity of the iterative design approach in identifying and correcting design flaws

35. Conclusions By focusing on simple and robust energy and electron transfer relays we can achieve functional variability by “mixing and matching” a few unique catalytic centers Protein de novo design is a useful way of constructing the relays that will provide building blocks for energy conversion systems

36. Collaboration • Avigdor Scherz • Alex Brandis • Oksana Shlyk-Kerner • Noy Group • Ilit Cohen-Ofri • Joanna Grzyb • Jebasingh Tennyson • Iris Margalit Zx Zx • Les Dutton • Chris Moser • Wolfgang Lubitz • Maurice van Gastel Ron Koder Vik Nanda ab ab Acknowledgments • Funding • Human Frontiers Science Program Organization • Weizmann InstituteNew Scientists Center Noam Adir, Technion Lev Weiner, Daniella Goldfarb • Israel Proteomics Center • Shira Albeck,Yoav Peleg,Tamar Unger