化工园为直通式反应器模拟自然热液系统
Summary
We describe chemical garden formation via injection experiments that allow for laboratory simulations of natural chemical garden systems that form at submarine hydrothermal vents.
Abstract
Here we report experimental simulations of hydrothermal chimney growth using injection chemical garden methods. The versatility of this type of experiment allows for testing of various proposed ocean / hydrothermal fluid chemistries that could have driven reactions toward the origin of life in environments on the early Earth, early Mars, or even other worlds such as the icy moons of the outer planets. We show experiments that include growth of chemical garden structures under anoxic conditions simulating the early Earth, inclusion of trace components of phosphates / organics in the injection solution to incorporate them into the structure, a switch of the injection solution to introduce a secondary precipitating anion, and the measurement of membrane potentials generated by chemical gardens. Using this method, self-assembling chemical garden structures were formed that mimic the natural chimneys precipitated at submarine hydrothermal springs, and these precipitates can be used successfully as flow-through reactors by feeding through multiple successive “hydrothermal” injections.
Introduction
“化学花园”是自组装开发无机沉淀物，其中对比化学物质的两种流体交互1,2。这些自组装的无机结构已经超过一个世纪的部分原因是由于他们的仿生外观的科学兴趣的主题，许多实验和理论研究已经进行，以了解化学园林系统3的各种复杂问题和可能的功能。化学园林自然的例子包括矿物“烟囱”的沉淀，围绕热水泉和冷泉增长，有人认为，这些可以提供合理的环境中生活出现4。为了发展一个化工园区模拟自然的热液喷口烟囱，水库的解决方案应该代表一个模拟的海洋成分和注射液应代表热液流体送入大海。这种O型的多功能性˚F实验不同的反应系统可以模拟几乎任何提议的海洋/热液流体化学，包括对早期地球或其它星球上的环境。在早期地球，海洋本来缺氧，酸性（pH值5-6），并且将含有溶解大气 CO 2和Fe 2+，以及铁III，镍离子， 锰离子，编号3-和NO 2 – 。此海水和超基洋壳之间的化学反应会产生含有氢和甲烷的碱性热液，在某些情况下硫化物（HS – ）4-8。形成在早期地球碱性通气环境烟囱可由此包含亚铁/铁羟基氧化物和铁/镍硫化物，并且已经提出，这些矿物质可能起到特定的催化和原酶功能朝向利用地球化学氧化还原/ pH梯度来驱动Metaboli游戏的出现SM 5。同样，在其他世界如可承办（或已托管）水/岩界面 – 例如早期的火星，木星的卫星木卫二，或土星的卫星土卫二 – 有可能是水/岩的化学能产生碱性发泄的环境能够驾驶生命起源前化学甚至提供可居住龛现存生命5,9-11。
经典的化学园实验涉及晶种的金属盐，例如，四水合氯化亚铁的FeCl 2•4H 2 O，浸没在含有反应性的阴离子， 如硅酸钠或“水玻璃”的溶液。金属盐溶解，创建包含的 Fe 2+的酸性溶液，随着更多的碱性溶液接口（含硅酸盐阴离子和OH – ）和被形成的无机膜的沉淀。在渗透压的膜膨胀，破裂，然后重新沉淀的t是新的流体界面。这个过程一直重复，直到晶体溶解，从而产生一个垂直取向的，自组织的沉淀结构具有复杂的形态在宏观和微观尺度。此沉淀过程导致横跨无机化学花园膜化学反衬解决方案的持续分离，带电物质穿过膜的差产生了膜电位12-14中 。化学花园结构是复杂的，表现出组分梯度从内部到外部13,15-19，和该结构的壁保持对比解决方案之间的分离很长时间，同时保持稍微渗透到离子。除了是一个理想的实验中用于教育目的（因为它们是简单，使课堂演示，并能教育学生的化学反应和自组织），化工园有科学意义的自我assemb交涉LY在动态，远离平衡系统，涉及可导致生产性的和有用的材料20,21的方法。
化学园林在实验室也可以通过注射方法进行培养，其中含有一种离子沉淀的溶液缓慢注入到包含所述共沉淀离子（或离子）的第二溶液。这导致类似于晶体生长实验化学花园结构的形成，不同之处在于该系统的性能和沉淀可更好地控制。注射方法有几个显著优点。它允许一个使用沉淀或结合物种的任何组合，以形成化学花园; 即多个沉淀离子可以结合到一个解决方案，和/或其它非沉淀组分可以被包括在任溶液，以吸附与沉淀物/反应。在化学产生的膜电位花园系统可以在注射实验来测定，如果一个电极结合到结构的内部，因此能够使系统的电化学研究。注射实验提供通过改变喷射率或总注射体积喂注射溶液成的化学园的内部受控的时间框架中的能力;因此，可以通过不同的解决方案依次饲料和使用沉淀的结构为陷阱或反应器中。结合，这些技术允许实验室模拟，可以在一个海底热液通风口都发生在一个天然化学花园系统的复杂过程，包括来自海洋之间许多同时沉淀反应形成的烟囱和泄流体（例如，制备金属硫化物，氢氧化物和/或碳酸盐和硅酸盐）5,22。这些技术也可以应用到任何化学花园反应体系，以允许形成新类型的的材料， 例如，分层管或管与吸附的反应性物质20,23。
我们这里详细的示例实验，其中包括两种化学花园，铁2+含结构在缺氧环境中的同步增长。在这个实验中，我们引入多磷酸盐和/或氨基酸的痕量到初始注射溶液，观察它们对结构的影响。的化工园区初步形成后，我们再切换注射液引入硫化物作为二次沉淀阴离子。膜电位的测定是在整个实验自动进行。本协议描述如何运行两个实验，在使用双注射泵一次;示所需的数据此过程的多次运行。相对较高的流量，在我们的实验中使用的水库和反应物浓度低pH值的目的是形成大烟囱沉淀在时间SC麦芽啤酒适合一天的实验室实验。然而，流体的流速在天然热水泉可以更加分散和（在早期地球系统 ，例如，Fe和S）沉淀物的浓度可能是震级低 4的命令;因此，结构化的沉淀物会形成较长的时间尺度和通风口可以活跃多年24,25几万。
Protocol
Representative Results
Discussion
通过注射方法的化学花园结构的形成可以通过连接包含产生沉淀反应离子任何两个解决方案来实现。有许多可能的反应系统，将产生的沉淀物的结构并发现反应离子和浓度的权利配方以生长所需结构是试验和错误的问题。注射溶液的流速由一个可编程注射器泵控制，这也可以实验之间变化，以模拟在自然系统中的流体流动的速率不同。化学园林结构取决于很多因素，包括组合物和流量，并且它是?…
Declarações
The authors have nothing to disclose.
Acknowledgements
This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We acknowledge the support by the NASA Astrobiology Institute (Icy Worlds). L.M.B. is supported by the NAI through the NASA Postdoctoral Program, administered by Oak Ridge Associated Universities through a contract with NASA. J.E.N. was supported through a US Department of Education PR/Award #: P031C110019 administered through Citrus College. We acknowledge useful discussions with members of the NAI Thermodynamics, Disequilibrium, and Evolution Focus Group and the Blue Marble Space Institute of Science.
Materials
| Syringe Pump | Fisher | 14-831-3 | Dual or multiple channel, depending on desired number of simultaneous experiments |
| Ferrous chloride tetrahydrate | Fisher | I90500 | Ferrous Chloride Tetrahydrate (Crystalline/Certified) |
| Ferric chloride hexahydrate | Fisher | I88-100 | Ferric Chloride Hexahydrate (Lumps/Certified ACS) |
| Sodium hydroxide | Sigma-Aldrich | S5881 | reagent grade, ≥98%, pellets (anhydrous) |
| Sodium sulfide nonahydrate | Fisher | S425212 | Sodium Sulfide Nonahydrate (Crystalline/Certified ACS). Store at -20C. Only open in a glove box or fume hood. Releases toxic H2S gas; all sulfide-containing solutions must be kept in a glove box or fume hood. |
| Potassium pyrophosphate | Sigma-Aldrich | 322431 | 97%, http://www.sigmaaldrich.com/catalog/product/aldrich/322431?lang=en®ion=US |
| L-Alanine | Sigma-Aldrich | A7627 | http://www.sigmaaldrich.com/catalog/product/sigma/a7627?lang=en®ion=US |
| Syringes (10cc) | Fisher | 14-823-16E | BD™ Syringe with Luer-Lok Tips (Without Needle) |
| Syringe needles (16 gauge) | Fisher | 14-826-18B | BD™ General Use and PrecisionGlide Hypodermic Needles, 16 G x 1.5 in. (38mm) |
| Tubing | Cole Parmer | EW-06407-71 | Tygon Lab Tubing, Non-DEHP, 1/16"ID X 1/8"OD |
| Aluminum seals | Fisher | 0337523C | Thermo Scientific™ National™ Headspace 20mm Crimp Seals |
| Gray butyl stoppers | Fisher | 0337522AA | Thermo Scientific™ National™ 20mm Septa for Headspace Vials |
| Serum bottles | Sigma-Aldrich | 33110-U | Vials, crimp top, serum bottle, size 100 mL, clear glass, O.D. × H 51.7 mm × 94.5 mm. For these experiments, the bottom of the serum bottle should be cut off. |
| Pipette tips | VWR | 53511-682 | pipette tips 0.5-10 microliters |
| Wire | McMaster-Carr | 8073K661 | Solid Single-Conductor Wire, UL 1007/1569, 20 AWG, 300 VAC |
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