Prebiotic Chemstry

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), PO4-3, 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), PO4-3, 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), PO4-3, ribose. • 3. Proper conditions

8. Today’s Atmosphere • Oxidizing: N2, O2, CO2, H2O • Organic Molecules are oxidized. • CH4 + 2 O2 -> CO2 + 2 H2O • Unique to Earth. • Fe3+; Fe(OH)3, Ksp ~ 10-39.

9. A. I. Oparin, 1938 • The Origin of Life. (Dover, 2nd edition) • Original atmosphere- reducing. • H2, CO, CH4, NH3, H2O, (H2S). • Oxygen is the result of Life on Earth. • Fe2+ primary form of iron.

10. Miller-Urey Experiment • 1950. • Reacted Mixture of CH4, NH3, H2, H2O.

11. Miller-Urey Experiment • 1950. • Reacted Mixture of CH4, NH3, H2, H2O. • 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. • + H2S -> 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. 15N/14N 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. 1st prokaryotes, photosynthesis produces O2. • 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!