Titel: Distinguished Speaker Seminar Series
Startdatum: Februar 04
Startzeit: 03:00 pm
Endzeit: 04:00 pm

Prof. Dr. Dieter Braun
Systems Biophysics
LMU Munich
Title: "Recreating first steps of Life using non-equilibrium and 2’,3’-Nucleotides"
Abstract: How could life emerge on the early Earth? Our experiments probe the first steps of molecular evolution by non-equilibrium experiments. We have revisited the polymerization and templated ligation from nucleotides with 2’,3’ cyclic phosphates as prebiotic plausible and mild activation group. In contrast to the unreactive cAMP studied in the 70s, we found low salt, low temperature conditions where cGMP is phosphorylating, polymerizing and ligating in the wet-dry cycles of heated gas bubbles. The chemistry is slower than others, but lacks side products and is open to direct recycling without additional catalysts. By combining it with physical non-equilibria, we think that there is a good chance to follow a line from nucleosides to the emergence of replication and selection for the first steps of Darwinian evolution. 

Above is backed up by experiments and finite element theory studying temperature gradients at heated air-water interfaces. These environments accumulate molecules, select them for length, enable the strand separation of RNA and allow continuous feeding of fresh molecules. Using sequencing, we see diverse networks emerging from the templated ligation of random oligonucleotides. In many cases, these studies are still performed with the help of proteins to gain speed, but using 2’,3’ cyclic nucleotides we converge towards conditions that allow RNA only experiments and to not require long Ribozymes or hydrolyzing magnesium. By balancing prebiotic chemistry with the physics of surface tension, evaporation, CO2, thermophoresis and gravity in heated chambers we progress to understand the autocatalytic networks that could lead to Darwinian evolution from only two molecules.

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