1. Lipidia : An Artificial Chemistry of Self-Replicating Assemblies of Lipid-like Molecules ”Lipid World” Modeling a ”Lipid World” scenario Origin of Life of Origin of Life Barak Naveh, Moshe Sipper, Doron Lancet and Barak Shenhav

2. RNA World Scenario catalysts templates §RNA molecules can act as catalysts in addition to acting as templates. §In theory §In theory, some molecules might be able to store genetic information and to catalyse their own creation. self-replicators §Such molecules will become self-replicators. §In practice §In practice, could be very difficult, especially in the putative pre-biotic conditions.

3. on its own §Observation: No bio-molecule is known to self- replicate on its own. molecular ensemble §Hypothesis: Self-replication may not have been achieved by a single molecule, but rather by a molecular ensemble. “Lipid World” §The “Lipid World” scenario: non-covalent assemblieslipid-like mutually catalytic sets assumes self-replication was first achieved by non-covalent assemblies of lipid-like molecules that contained mutually catalytic sets. A Lipid World Scenario

4. Why Lipids? §Likely to have been present in early earth. self-organize into higher level structures §Naturally self-organize into higher level structures.

5. Primitive Growth and Division §assemblies amphiphiles §assemblies of lipid-like molecules (amphiphiles). §a primitive form of growth and division. capable of self-replication §a process that, though noisy, is capable of self-replication. §reasonable fidelity.

6. Could Be Useful As §Stable self-replicating micro-environments. §Polymerizers / Reactors. §Surface templating (Rasmussen, 2002) G A G A

7. The GARD Model join §Molecules from the environment may join the assembly. leave §Molecules may leave the assembly. rates §Join and Leave rates are enhanced by catalysis, depending on the compositions of the assembly and the environment. Graded Autocatalysis Replication Domain

8. Lipidia Assemblies are colored according to species. Environment Environment with free molecules. Assemblies Assemblies of molecules recruited from the environment. GARD Assembly dynamics modeled using GARD model.

9. Grid Dynamics diffusion environment diffusion drift assembly drift

10. GARD and Lipidia §infinite §infinite environment: §assembly's effect on the environment is not modeled. §food molecules are in infinite supply. §one assembly at a time. § finite environment grid location § finite environment for every grid location. grid § based on a 2D grid. assemblies § locations may contain zero or more assemblies of molecules. § many assemblies in parallel. § birth, death, diffusion, and more… Basic GARD Lipidia ??

11. Results Infinite Environment Finite Environment

12. Results (summary) Infinite Infinite env. Finite Finite env. No. species after 15M reactions 51135 Time to first 50 species 628

13. Results (cont.) validated §GARD is validated for finite environment. finite environmentmore species faster §A finite environment produces more species, and faster, than an infinite environment. finite environmentmore assemblies more species §A finite environment allows more assemblies to occur in more species and in greater numbers. population diversity increases §Assembly population diversity increases.

14. Conclusions might help to “do more” §One might think: An infinite supply of resources, in the form of “food” molecules, might help to “do more”. helps to “do more of the same” §Our findings show it only helps to “do more of the same”. §Diversityresourcesare limited §Diversity seems to spring when resources are limited.

15. Barak Naveh, Moshe Sipper Dept. of Computer Science, Ben-Gurion University, Israel Doron Lancet, Barak Shenhav Dept. Molecular Genetics and the Crown Human Genome Center, Weizmann Institute of Science, Israel http://ool.weizmann.ac.il/lipidia