'14 セミナー日程表

seminar top

市川研究室主催

Time 7/4(Fri.) 10:30-12:00
Place 理学部5号館401号室 (Kyoto Univ. Science Bldg. V, Rm. 401)
Speaker Dr. Christof Mast
Affiliation Systems Biophysics, Functional Nanosystems Ludwig Maximilians University Munich
Title Towards Molecular Evolution Driven by Thermal Traps
Abstract Biopolymers like RNA, DNA and proteins are the fundamental actors in all life on earth. It is however unclear, how the first RNA polymers with enzymatic activity could arise in a prebiotic scenario: Even in millimolar concentrations, ribonucleic acids only build short polymers with a length of 20 bases. We demonstrate how a reversible polymerization process can be enhanced with the help of a simple thermal gradient [1]. Situated in an elongated compartment comparable to a hydrothermal pore it will create a convective fluid flow and also push biomolecules along the thermal gradient due to thermophoresis. The physical non-equilibrium setting of this so-called thermal trap is able to selectively accumulate longer polymers exponentially better than shorter polymers. Since the formation of longer polymers is coupled to higher local monomer concentrations, polymerization and thermal trapping are mutually self-enhancing. This process is described by a theory of trapped polymerization which we experimentally validated with the reversible polymerization of sticky-ended dsDNA blocks (monomers) in a laser-driven thermal trap. The extrapolation of the theory toward the RNA-world scenario shows that a pore height of 5 cm and a temperature difference of 10 K are sufficient to form RNA polymers longer than the shortest RNA based replicator. In the experimental setting, the superposition of two perpendicular convection flows and thermophoresis also supported the formation of large (~100?m) and specific DNA aggregates made of polymerizing DNA monomers: The melting temperature of the aggregates and the sticky ends of the DNA monomers match. No aggregates were found using non-polymerizing monomers with randomized sticky-ends. Such specific aggregation of genetic material could have lead to the selection of sequences by their structural stabilization. The replication of genetic molecules is central to Darwinian evolution. We demonstrate how a laser-driven thermal trap is able to drive an exponential replication reaction via thermal cycling and at the same time protects the replication products against outward diffusion into the diluted reservoir [2]. In a proxy replication reaction, DNA replicating polymerase is able to double the amount of a 143mer product each 50 s, while the time constant for accumulation is 92 s. Thermal traps could therefore represent a possible non-equilibrium environment for the formation and replication of the first biopolymers - essential ingredients for the start of molecular evolution.

過去のセミナー

セミナー主催研究室について

京都大学大学院 理学研究科  物理学第一教室 
市川研究室



Please contact this E-mail address, whenever you have some questions about seminars.
(semimaster@chem.scphys.kyoto-u.ac.jp)