title: Polymer GARD: computer simulation of covalent bond formation in reproducing molecular assemblies.
abstract: The basic Graded Autocatalysis Replication Domain (GARD) model consists of a repertoire of small molecules, typically amphiphiles, which join and leave a non-covalent micelle-like assembly. Its replication behavior is due to occasional fission, followed by a homeostatic growth process governed by the assembly's composition. Limitations of the basic GARD model are its small finite molecular repertoire and the lack of a clear path from a 'monomer world' towards polymer-based living entities. We have now devised an extension of the model (polymer GARD or P-GARD), where a monomer-based GARD serves as a 'scaffold' for oligomer formation, as a result of internal chemical rules. We tested this concept with computer simulations of a simple case of monovalent monomers, whereby more complex molecules (dimers) are formed internally, in a manner resembling biosynthetic metabolism. We have observed events of dimer 'take-over' - the formation of compositionally stable, replication-prone quasi stationary states (composomes) that have appreciable dimer content. The appearance of novel metabolism-like networks obeys a time-dependent power law, reminiscent of evolution under punctuated equilibrium. A simulation under constant population conditions shows the dynamics of takeover and extinction of different composomes, leading to the generation of different population distributions. The P-GARD model offers a scenario whereby biopolymer formation may be a result of rather than a prerequisite for early life-like processes.
authors: Department of Molecular Genetics and the Crown Human Genome Center, the Weizmann Institute of Science, Rehovot, Israel.
authors: Barak
authors: B
authors: Shenhav
authors: Arren
authors: A
authors: Bar-Even
authors: Ran
authors: R
authors: Kafri
authors: Doron
authors: D
authors: Lancet
mesh_terms: D003198:Computer Simulation; D019418:Evolution, Chemical; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D012984:Software; D013816:Thermodynamics
chemical_list: D011108:Polymers