1. Prebiotic Chemstry Jeff G. Wardeska, PhD Jan. 24, 2008

2. Two Questions  1. How were the molecules necessary for the first living organisms synthesized?  2. Could life as we know it exist elsewhere in the universe?

3. 1. How were the necessary molecules for the first living organisms synthesized?  What molecules are needed to make the simplest cell, e.g., virus?

4. 1. How were the necessary for the first living organisms synthesized?  What molecules are needed to make the simplest cell, e.g., virus? –1. Protein; 20 amino acids.

5. 1. How were the necessary molecules for the first living organisms synthesized?  What molecules are needed to make the simplest cell, e.g., virus? –1. Protein; 20 amino acids. –2. DNA; 4 bases (A, G, C, T), PO 4 -3, ribose.

6. 1. How were the necessary molecules for the first living organisms synthesized?  What molecules are needed to make the simplest cell, e.g., virus? –1. Protein; 20 amino acids. –2. DNA; 4 bases (A, G, C, T), PO 4 -3, ribose.

7. 1. How were the necessary molecules for the first living organisms synthesized?  What molecules are needed to make the simplest cell, e.g., virus? –1. Protein; 20 amino acids. –2. DNA; 4 bases (A, G, C, T), PO 4 -3, ribose. –3. Proper conditions

8. Today ’ s Atmosphere  Oxidizing: N 2, O 2, CO 2, H 2 O  Organic Molecules are oxidized.  CH 4 + 2 O 2 -> CO 2 + 2 H 2 O  Unique to Earth.  Fe 3+ ; Fe(OH) 3, Ksp ~ 10 -39.

9. A. I. Oparin, 1938  The Origin of Life. (Dover, 2 nd edition)  Original atmosphere- reducing.  H 2, CO, CH 4, NH 3, H 2 O, (H 2 S).  Oxygen is the result of Life on Earth.  Fe 2+ primary form of iron.

10. Miller-Urey Experiment  1950.  Reacted Mixture of CH 4, NH 3, H 2, H 2 O.

11. Miller-Urey Experiment  1950.  Reacted Mixture of CH 4, NH 3, H 2, H 2 O. Produced about 20 amino acids (<2% yield, each),+ HCN. Reacted about 15% of C.

12. Miller-Urey, cont ’ d  Can form amino acids under a variety of conditions; –UV light energy. –Sound. –Heat. –+ H 2 S -> cysteine. –HCN -> A, G –+HCCCN -> C, U (Cyanoacetylene)

13. What ’ s the evidence that this chemistry might have actually happened?  Murchison Meteorite, Australia, 1969.  Geologic Record.

14. Murchison Meteorite  Sept. 1969, Australia

15. Murchison Meteorite  1. Large number of amino acids, > 50 not found on earth.  2. Slight enantiomeric excess of l- enantiomers in some.  3. Diff. 15 N/ 14 N ratio from terrestial samples. Same ratio in both d & l enantiomers.

16. Precambrian Era, Mya

17. Precambrian, cont ’ d.  3800. Oldest rocks, oceans form.  3500-2800. 1 st prokaryotes, photosynthesis produces O 2.  2800-1600. Banded Iron Formations.

18. Stromatolites

19. Banded Iron Formations

20. Issues  Origin of l-forms of amino acids.  Mechanism of synthesis of nucleosides and nucleotides.  Chicken vs. egg; which came first, DNA or proteins? –RNA world?

21. Are we alone?

22. Further reading  Stanley L. Miller and Leslie E. Orgel, “ The Origins of Life on the Earth ”, Prentice-Hall, 1974.  Antonio Lazcano* and Stanley L. Miller, “ The Origin and Early Evolution. Review of Life: Prebiotic Chemistry ”, the Pre-RNA World, and Time. Cell, Vol. 85, 793 – 798, June 14, 1996.  Leslie E. Orgel, “ Prebiotic Chemistry and the Origin of the RNA World ”, Critical Reviews in Biochemistry and Molecular Biology, 39:99 – 123, 2004

23. Thank You!