1. Homochirality: models and results Axel Brandenburg, Anja Andersen, Susanne Höfner, Martin Nilsson To appear in Orig. Life Evol. Biosph., q-bio.BM/0401036

2. 2 Photosynthesis Requires chlorophyll as catalyst What about chiralitry?

3. 3 Aminoacids in protein: left-handed Sugars in DNA and RNA: right-handed Louis Pasteur (1822-1895) animogroup carboxylgroup

4. 4 Racemic mixture (from lecture of Antoine Weiss) Racemization  dating method

5. 5 Miller/Urey experiment 15 organic compounds 2% amino acids (11 different ones) racemic mixture Wait 1 week

6. 6 Chirality and origin of life Dead stuff not chiral, so is chirality –with racemic mixture: structure fragile Importance: –Prerequisite of life (provides curvature and twist) –Consequence of life (enzymatic reactions) Miller-Urey amino acids: both chiralities –in Murchison meteorite: mostly left-handed! –but contamination is debated… Reasons discussed: circularly polarized light, beta- decay (weak force), homochiral template

7. 7 Relevant experiments: nucleotides template-directed oligomerization poly (C D )  oligo (G D )  Mononucleotides with wrong Chirality terminate chain growth cytosine guanine ok poisoned Joyce, et al. (incl. Orgel) (1984) (using HPLC)

8. 8 Contergan: was sold as racemic mixture causes misformations Cures morning sickness during pregnancy (abundaned in December 1961)

9. 9 Relevant experiments: crystals Crystal growth with stirring: primary nucleation suppressed Crystal growth, many different nucleation sites: racemic mixture Autocatalytic self-amplification? Frank (1953), Goldanskii & Kuzmin (1989), …

10. 10 Auto-catalytic effect in dead matter Alkanol with 2% e.e. Treated with carboxylaldehyde

11. 11 Model by Saito & Hyuga (Jan 2004) Bimodal behavior

12. 12 Model by Sandars (Dec 2003, OLEB) Reaction for left-handed monomers Loss term for each constituent

13. 13 Combined equations Loss term for each constituent

14. 14 Including enantiomeric cross-inhibition Loss term for each constituent Racemic solution ~2 1-n

15. 15 Coupling to substrate S Q L comes from substrate acts as a sink of S S sustained by source Q Catalytic properties of substrate (depending on how much L and R one has)  Q L = Q R (L n,R n ) Source of L 1 monomers Q L

16. 16 Self-catalytic effect Form of Q L = Q R (L n,R n ) Possible proposals for C L (similarly for C R )

17. 17 Birfurcation properties  Mononucleotides with wrong Chirality terminate chain growth

18. 18 Stability Relative perturbation of racemic solution, 10 -4

19. 19 Conservation law Dependence on fidelity where

20. 20 Differences to Sandars Coupling to substrate: here proportional to E L –in Sandars: [L N ] Outer boundary condition: here open –in Sandars: prescribed damping term Future extensions: –Chain braking –add spatial 3D dynamics

21. 21 Reduced equations Quantitatively close to full model

22. 22 Initial bias Effect in reality very weak

23. 23 Spatially extended model Propagating front solutions Reaction-diffusion equation Proto type: Fisher’s equation wave speed with Tuomas Multamäki

24. 24 1D model (reaction-diffusion equation) Propagation into racemic environment

25. 25 2D model (reaction-diffusion equation) Short run

26. 26 2D model (reaction-diffusion equation) Time scale longer than for simple fronts

27. 27 P polymerization olymerization in 1D chain growth, Rn and Ln in different places

28. 28 The RNA world Central dogma of chemistry of life –DNA  RNA  protein enzyme all enzymes are themselves proteins? Walter Gilbert (1986)

29. 29 RNA itself as enzyme

30. 30 pre-RNA worlds Many problems: stability of sugars 2-amino ethyl glycin (AEG)

31. 31 pre-RNA worlds PE Nielsen (1993) better alternative: Nelson, Levi, Miller (2000)