Dieter Braun

The hallmark of living matter is the replication of genetic molecules and their active storage against diffusion. We have argued in the past that thermal convection can host the million-fold accumulation even of single nucleotides and at the same time trigger exponential replication [1]. Accumulation is driven by thermophoresis and convection in elongated chambers, replication by the inherent temperature cycling in convection. Optothermal pumping [2,3] allows to implement the thermal trap efficiently in a toroidal [4] or linear [5] geometry.

Based on this method, we were in a position to combine accumulation and replication of DNA in the same chamber [5]. As we are missing a solid chemistry of prebiotic replication, we used as a proxy reaction for to replication the polymerase chain reaction. The experiments explore conditions in pores of hydrothermal rock which can serve as a model environment for the origin of life and has prospects towards the first autonomous evolution, hosting the Darwin process by molecular selection using the thermophoretic trap. On the other side, the implemented continuous evolution will be able to breed well specified DNA or RNA molecules in the future.

Life signals most of its information by the interaction of molecules. It is important to quantify both the interaction strength and the reaction speed to understand the detailed function of biological reaction networks. Methods are still lacking to measure both in complex biological liquids such as blood serum or cell lysate.

We found that the movement of proteins in a temperature gradient is a sensitive and versatile way to probe protein interactions, including the important class of membrane receptors binding to its target molecule [6]. The binding was detected all-optically in various biological fluids. We screened for drug-protein interactions without labeling the protein and were able to successfully commercialize the method [7]. The physical basis of the movement was studied with DNA and polystyrene beads and could be understood with a capacitor model of ionic shielding.

We managed to measure the reaction speed inside living cells using fast temperature oscillations and a molecular lock-in method. Maps of the reaction speed reveal both faster and slower reactions as compared to outside the cell [8]. This indicates a complex kinetic control of cellular reactions.

[1] Baaske, Weinert, Duhr, Lemke, Russell and Braun, PNAS 104, 9346 (2007)

[2] Weinert, Kraus, Franosch and Braun, PRL 100, 164501 (2008)

[3] Weinert and Braun, Journal of Applied Physics 104, 104701 (2008)

[4] Weinert and Braun, Nano Letters 9, 4264 (2009)

[5] Mast and Braun, PRL 104, 188102 (2010)

[6] Wienken, Duhr and Baaske et.al. Nature Communications 1, 100 (2010)

[7] Wang, Baaske et.al., PNAS, accepted

[8] Schoen, Krammer and Braun, PNAS 106, 21649 (2009)