Statistical and Biological Physics

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Escalation of polymerization in a thermal gradient

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

In cells, long DNA and RNA polymers are formed with the help of sophisticated enzymes.
However, it is unclear how these information-carrying polymers could have spontaneously formed in the "premordial soup" without enzymes. Here, we demonstrate a mutual positive feedback between the chemical polymerization reaction and a physical non-equilibrium process. This feedback circle leads to a dramatic enhancement of the probability to generate long molecules from dilute solutions of monomers.

The physical nonequilibrium is provided by a thermal gradient, which creates a molecule trap that preferentially accumulates longer RNA molecules. We present experimental and theoretical evidence that thermal trapping enhances polymerization, which in turn enhances trapping, leading to an escalation of polymerization. Our results show that a simple thermal gradient can significantly enlarge the available sequence space for the emergence of catalytically active polymers.