The tree of life: Darwinian chemistry as the evolutionary force from cyanic acid to living molecules and cells

Transcription

1 The tree of life: Darwinian chemistry as the evolutionary force from cyanic acid to living molecules and cells Nils G. Walter Chemistry

2 So far we are here Chemistry Chemical Evolution Self-organization Biological Evolution How do we get here? Voet & Voet, Biochemistry

3 Cyanic acid and friends: The molecules at the root 1953, U. Chicago: Stanley L. Miller & Harold C. Urey

4 How complex organic molecules formed L.E. Orgel, Scientific American 10/ : U. Houston Juan Oro

5 The basic building blocks Amino acids Nucleo bases Lipids Sugars Voet & Voet, Biochemistry

6 Building larger, biological molecules: Condensation and (hydrolytic) decay Nucleotide Clay pocket helps exclude water!

7 But wait if there is decay, doesn t the second Law of Thermodynamics ( entropy tends to increase ) drive everything back to square one? No, not if the system is far from equilibrium and an external energy source drives it to increasing complexity!!! Günter Wächtershäuser Pyrite

8 Pumping fuel into the system: Thioester formation High temperature acidic conditions (e.g., thermal vents) Christian de Duve Energy: ATP, PP i Pyrite, H 2 S Catalysts: RNA Reduction: Organic acids, aldehydes Pyrite

9 The resultant increase in entropy of the Universe leads to assembly of (bio)polymers: Example RNA Leslie Orgel RiboNucleic Acid Other (bio)polymers may have preceded RNA

10 The RNA World: Living molecules L.E. Orgel, Scientific American 10/1994

11 Driving force of evolution: Darwinian chemistry Replication, Mutation, Selection Genotype: Sequence Replication Energy Mutation: Quasispecies Phenotype: Structure, Function Selection

12 Rebuilding the RNA World, one function at a time RNA Replicase: 2001, Bartel et al. RNA Nucleotide Synthase: 1998, Unrau & Bartel Peptide bond formation by the ribosome is catalyzed by the RNA component: 2000, Moore & Steitz Johnston et al., Science 292 (2001) 1319; Chapple, Bartel, Unrau, RNA 9 (2003) 1208 Nissen, Hansen, Ban, Moore, Steitz, Science 289 (2000) 905

13 Towards ever higher complexity why, and what are fractals? Fractals are complex, selfsimilar geometric structures from simple mathematical rules feedback loops generate fractal geometries in nature

14 Hypercycles and Metabolism Manfred Eigen M. Eigen, W. Gardner, P. Schuster, R. Winkler-Oswatitsch, Scientific American 4/1981

15 Primitive cells in the primordial world: Distinction between self and non-self dies out

16 Transitions to an RNA-protein, then the modern DNA-RNA-protein world DNA RNA RNA RNA protein protein Pictures from: Ramakrishnan, Cell 108 (2002) 557; Nissen, Hansen, Ban, Moore, Steitz, Science 289 (2000) 905; Sawaya, Guo, Tabor, Richardson, Ellenberger, Cell 99 (1999) 167; Torres_Larios, Swinger, Krasilnikov, Pan, Mondragon, Nature 437 (2005) 584

17 Chemical Evolution took billions of years, but left few traces Chemical Evolution J.P. Gogarten, J.P. Townsend, Nat. Reviews Microbiol. 3 (2005) 679

18 Junk DNA and HIV: Modern evidence for the RNA World 98% of the human genome are junk DNA Such junk DNA plays important, still ill-understood roles in the regulation and maintenance of our genome While RNA viruses like HIV are modern, they may be analogs of ancient, minimal RNA organisms F.F. Costa, Gene 357 (2005) 83

19 Summary: From Astrophysics to Biology The force is with Chemistry /////// Chemistry