波浪形膜和平面化学花园的生长速率：增强的扩散和生物能量学
Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics
摘要：
为了模拟Hadean热液喷口中原始细胞膜的离子传输，我们从理论和实验两方面考虑在二维微流控反应器中两个平行流体流之间的界面处形成的沉淀膜的平面生长。沉淀物的生长速率与时间的平方根成正比，这是扩散输运的特征。然而，氢氧化物和金属离子的浓度的生长速率的依赖性是近似线性和二次，分别。我们表明，这种差异的离子传输动力学产生的增强运输的金属离子在整个薄的凝胶层存在于沉淀物的表面。在这个波浪状多孔凝胶层中的横向速度的波动允许阳离子的增强的运输，使得有效扩散率比仅从分子扩散预期的高大约一个数量级。我们的理论预测与我们对微流体通道中氢氧化锰膜生长的实验室测量非常一致，并且这种增强的运输被认为是第一个单细胞生物体的生物能量学所必需的。
英文摘要：
In order to model ion transport across protocell membranes in Hadean hydrothermal vents, we consider both theoretically and experimentally the planar growth of a precipitate membrane formed at the interface between two parallel fluid streams in a two-dimensional microfluidic reactor. The growth rate of the precipitate is found to be proportional to the square root of time, which is characteristic of diffusive transport. However, the dependence of the growth rate on the concentrations of hydroxide and metal ions is approximately linear and quadratic, respectively. We show that such a difference in ionic transport dynamics arises from the enhanced transport of metal ions across a thin gel layer present at the surface of the precipitate. The fluctuations in transverse velocity in this wavy porous gel layer allow an enhanced transport of the cation, so that the effective diffusivity is about an order of magnitude higher than that expected from molecular diffusion alone. Our theoretical predictions are in excellent agreement with our laboratory measurements of the growth of a manganese hydroxide membrane in a microfluidic channel, and this enhanced transport is thought to have been needed to account for the bioenergetics of the first single-celled organisms.
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