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Heat flux across an open pore enables the continuous replication and selection of oligonucleotides towards increasing length


The replication of nucleic acids is central to the origin of life. On the early Earth, suitable non-equilibrium boundary conditions would have been required to surmount the effects of thermodynamic equilibrium such as the dilution and degradation of oligonucleotides. One particularly intractable experimental finding is that short genetic polymers replicate faster and outcompete longer ones, which leads to ever shorter sequences and the loss of genetic information. Here we show that a heat flux across an open pore in submerged rock concentrates replicating oligonucleotides from a constant feeding flow and selects for longer strands. Our experiments utilize the interplay of molecular thermophoresis and laminar convection, the latter driving strand separation and exponential replication. Strands of 75 nucleotides survive whereas strands half as long die out, which inverts the above dilemma of the survival of the shortest. The combined feeding, thermal cycling and positive length selection opens the door for a stable molecular evolution in the long-term microhabitat of heated porous rock.

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Figure 1: Reduction of local entropy is key for living systems and can be caused by the flux of thermal energy.
Figure 2: Accumulation of oligonucleotides.
Figure 3: Heat-driven filter selecting for strand length.
Figure 4: Selection of a replicating DNA population that occupies the thermal habitat.

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We thank N. Osterman and C. Mast for the preliminary trapping experiments and discussions, M. Herzog and M. Reichl for thermophoresis measurements and S. Krampf for help with the gel electrophoresis. Financial support from the NanoSystems Initiative Munich, the Simons Collaboration on the Origin of Life, the Ludwig-Maximilians-Universität Munich Initiative Functional Nanosystems, the SFB 1032 Project A4 and the European Research Council (ERC) Starting Grant is acknowledged.

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M.K., L.K. and S.L. contributed equally to this work and performed the experiments. M.K., L.K., S.L and D.B. conceived and designed the experiments, analysed the data and wrote the paper.

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Correspondence to Dieter Braun.

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The authors declare no competing financial interests.

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Kreysing, M., Keil, L., Lanzmich, S. et al. Heat flux across an open pore enables the continuous replication and selection of oligonucleotides towards increasing length. Nature Chem 7, 203–208 (2015).

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