universal sequence replication, reversible polymerization and early functional biopolymers a model for the initiation of prebiotic sequence evolution通用序列复制,可逆聚合和早期功能生物聚合物的模型进化生命起源以前的序列的起始.pdf

Universal Sequence Replication, Reversible Polymerization and Early Functional Biopolymers: A Model for the Initiation of Prebiotic Sequence Evolution Sara Imari Walker1,2,3¤, Martha A. Grover1,2, Nicholas V. Hud1,3* 1 NSF/NASA Center for Chemical Evolution, Georgia Institute of Technology, Atlanta, Georgia, United States of America, 2 School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States of America, 3 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States of America Abstract Many models for the origin of life have focused on understanding how evolution can drive the refinement of a preexisting enzyme, such as the evolution of efficient replicase activity. Here we present a model for what was, arguably, an even earlier stage of chemical evolution, when polymer sequence diversity was generated and sustained before, and during, the onset of functional selection. The model includes regular environmental cycles (e.g. hydration-dehydration cycles) that drive polymers between times of replication and functional activity, which coincide with times of different monomer and polymer diffusivity. Template-directed replication of informational polymers, which takes place during the dehydration stage of each cycle, is considered to be sequence-independent. New sequences are generated by spontaneous polymer formation, and all sequences compete for a finite monomer resource that is recycled via reversible polymerization. Kinetic Monte Carlo simulations demonstrate that this proposed prebiotic scenario provides a robust mechanism for the exploration of sequence space. Introduction of a polymer sequence with monomer synthetase activity illustrates that functional sequences can become established in a