Regensburg 2013 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 32: Statistical Physics in Biological Systems III (joint with BP)

DY 32.9: Talk

Thursday, March 14, 2013, 17:00–17:15, H46

Symmetry Breaking of Sequence Information in Catalytic Polymer Soups — •Shoichi Toyabe and Dieter Braun — Systems Biophysics,Ludwig-Maximilians-University Munich, Munich

One of the most distinguished properties of living systems is that they sustain genetic information and reproduce it. However, its origin remains elusive; how can information emerge in the chaotic molecular soup in the prebiotic earth? We discuss models and preliminary experiments to show the emergence of order in a catalytic polymer solution. We argue that template-directed copolymerization of diverse polymers is a promising route. Autocatalytic copolymerization extends polymers stochastically. Interestingly, a numerical simulation shows that the polymers self-organize into an ordered state where a stochastically chosen small set of sequence motifs become dominant. This spontaneous symmetry breaking occurs because autocatalytic chain reactions in the reaction network interact competitively and amplify strands beyond exponential growth. This amplifies spontaneous fluctuations and sustains it by Darwinian selection against other sequences. The transition to the ordered state is accompanied by a population inversion, i.e. the length distribution of polymers was biased to the longer side at the ordered state. In order to demonstrate the symmetry breaking by experiments, we performed ligase chain reactions of DNA strands with semi-random sequences. Under nonequilibrium driving of material flux and temperature cycles, we observed a population inversion, which implies the breaking of the symmetry. Furthermore, we analyzed the sequences to confirm the symmetry breaking by on the basis of PCR.