Baaske Philipp, Weinert Franz M, Duhr Stefan, Lemke Kono H, Russell Michael J, Braun Dieter
Biophysics Department, Ludwig-Maximilians Universität München, Amalienstrasse 54, 80799 Munich, Germany.
Proc Natl Acad Sci U S A. 2007 May 29;104(22):9346-51. doi: 10.1073/pnas.0609592104. Epub 2007 May 9.
We simulate molecular transport in elongated hydrothermal pore systems influenced by a thermal gradient. We find extreme accumulation of molecules in a wide variety of plugged pores. The mechanism is able to provide highly concentrated single nucleotides, suitable for operations of an RNA world at the origin of life. It is driven solely by the thermal gradient across a pore. On the one hand, the fluid is shuttled by thermal convection along the pore, whereas on the other hand, the molecules drift across the pore, driven by thermodiffusion. As a result, millimeter-sized pores accumulate even single nucleotides more than 10(8)-fold into micrometer-sized regions. The enhanced concentration of molecules is found in the bulk water near the closed bottom end of the pore. Because the accumulation depends exponentially on the pore length and temperature difference, it is considerably robust with respect to changes in the cleft geometry and the molecular dimensions. Whereas thin pores can concentrate only long polynucleotides, thicker pores accumulate short and long polynucleotides equally well and allow various molecular compositions. This setting also provides a temperature oscillation, shown previously to exponentially replicate DNA in the protein-assisted PCR. Our results indicate that, for life to evolve, complicated active membrane transport is not required for the initial steps. We find that interlinked mineral pores in a thermal gradient provide a compelling high-concentration starting point for the molecular evolution of life.
我们模拟了受热梯度影响的细长热液孔隙系统中的分子输运。我们发现在各种各样的堵塞孔隙中分子会极度聚集。该机制能够提供高度浓缩的单核苷酸，适用于生命起源时RNA世界的运作。它仅由孔隙两端的热梯度驱动。一方面，流体通过热对流沿孔隙穿梭，而另一方面，分子在热扩散的驱动下穿过孔隙。结果，毫米级的孔隙能将单核苷酸在微米级区域内聚集超过10^8倍。在孔隙封闭底端附近的大量水中发现了分子浓度的增强。由于这种聚集与孔隙长度和温差呈指数关系，因此对于裂隙几何形状和分子尺寸的变化具有相当强的稳定性。细孔隙只能浓缩长链多核苷酸，而较粗的孔隙能同样良好地聚集短链和长链多核苷酸，并允许各种分子组成。这种环境还会产生温度振荡，此前已证明其能在蛋白质辅助的聚合酶链式反应中使DNA指数式复制。我们的结果表明，对于生命的演化而言，初始阶段并不需要复杂的主动膜运输。我们发现处于热梯度中的相互连接的矿物孔隙为生命的分子进化提供了一个极具吸引力的高浓度起始点。
