Escalation of polymerization in a thermal gradient

Christof B. Mast, Severin Schink, Ulrich Gerland, Dieter Braun

Research output: Contribution to journalArticlepeer-review

126 Scopus citations

Abstract

For the emergence of early life, the formation of biopolymers such as RNA is essential. However, the addition of nucleotide monomers to existing oligonucleotides requires millimolar concentrations. Even in such optimistic settings, no polymerization of RNA longer than about 20 bases could be demonstrated. How then could self-replicating ribozymes appear, for which recent experiments suggest a minimal length of 200 nt? Here, we demonstrate a mechanism to bridge this gap: the escalated polymerization of nucleotides by a spatially confined thermal gradient. The gradient accumulates monomers by thermophoresis and convection while retaining longer polymers exponentially better. Polymerization and accumulation become mutually self-enhancing and result in a hyperexponential escalation of polymer length. We describe this escalation theoretically under the conservative assumption of reversible polymerization. Taking into account the separately measured thermophoretic properties of RNA, we extrapolate the results for primordial RNA polymerization inside a temperature gradient in pores or fissures of rocks. With a dilute, nanomolar concentration of monomers themodel predicts that a pore length of 5 cm and a temperature difference of 10 K suffice to polymerize 200-mers of RNA inmicromolar concentrations. The probability to generate these long RNAs is raised by a factor of >10600 compared with polymerization in a physical equilibrium. We experimentally validate the theory with the reversible polymerization of DNA blocks in a laser-driven thermal trap. The results confirm that a thermal gradient can significantly enlarge the available sequence space for the emergence of catalytically active polymers.

Original languageEnglish
Pages (from-to)8030-8035
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume110
Issue number20
DOIs
StatePublished - 14 May 2013
Externally publishedYes

Keywords

  • (Nonenzymatic) emergence of RNA
  • Hydrothermal vents
  • Molecular evolution
  • Nonequilibrium
  • RNA world

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