An automated apparatus for he simulation of prebiotic wet-dry cycles under strictly anaerobic conditions
An automated apparatus for he simulation of prebiotic wet-dry cycles under strictly anaerobic conditions
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DOI：
10.1017/s1473550418000010
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发表时间：
2019-02-01
影响因子：
1.7
通讯作者：
Strasdeit, Henry
中科院分区：
文献类型：
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作者：
Fox, Stefan;Pleyer, Hannes Lukas;Strasdeit, Henry
早期地球上的生命起源前的化学演化可能部分是由环境波动驱动的，例如火山岩池中的干湿循环和温度循环。在这里，我们描述了新开发的“干湿装置”（WDA）的设置、操作原理和测试应用，该装置旨在模拟这种波动的环境。 WDA 允许调整循环持续时间、干湿阶段的温度以及有机和矿物成分，这些都是干湿模拟中的关键参数。然而，WDA 最重要的特点是（i）它是自动化的，这意味着无需操作员即可进行长时间实验；（ii）可以模拟早期地球地面大气层中几乎不存在游离氧的情况。在进入 WDA 之前，将 99.999% 的氮气通过串联的两种碱性连苯三酚溶液，从而实现严格的无氧条件。我们使用了三种化学系统来测试 WDA：(i) 存在和不存在粘土矿物的情况下的氨基酸甘氨酸，(ii) 存在和不存在矿物橄榄石的亚油酸（氧敏感两亲物），以及 (iii) 碱性连苯三酚溶液。我们观察到粘土矿物在干湿条件下极大地加速了甘氨酸的分解。甘氨酸肽作为次要产物形成。在甘氨酸实验过程中，我们开发了一种可靠的气相色谱方法来定量环状二肽 2,5-二酮哌嗪。空气和橄榄石都促进了干湿循环中亚油酸的分解。最后，对氧极其敏感的连苯三酚溶液被用作 WDA 中残留氧的颜色指示剂。我们实验室的模拟设施目前由八个相同的 WDA 和周围的基础设施组成。它可以提供给希望进行循环湿干实验的其他人。
Prebiotic chemical evolution on the early Earth may have been driven in part by fluctuating environments, for example wet-dry and temperature cycling in volcanic rock pools. Here, we describe the setup, operating principle and test applications of a newly developed 'wet-dry apparatus' (WDA) designed to simulate such fluctuating environments. The WDA allows adjusting the duration of the cycles, the temperature during the wet and dry phases and the organic and mineral components, which are all key parameters in wet-dry simulations. The WDA's most important features, however, are (i) that it is automated, which means that long-time experiments are possible without the need for an operator and (ii) that the virtual absence of free oxygen in the early Earth's atmosphere at ground level can be simulated. Rigorously oxygen-free conditions were achieved by passing 99.999% nitrogen gas through two alkaline pyrogallol solutions in series, prior to entering the WDA. We used three chemical systems to test the WDA: (i) the amino acid glycine in the presence and absence of clay minerals, (ii) linoleic acid (an oxygen-sensitive amphiphile) with and without the mineral olivine, and (iii) alkaline pyrogallol solution. We observed that clay minerals greatly accelerated the decomposition of glycine under wet-dry conditions. Glycine peptides were formed as minor products. In the course of the glycine experiments, we developed a reliable gas chromatographic method to quantify the cyclic dipeptide 2,5-diketopiperazine. The decomposition of linoleic acid in wet-dry cycles was promoted by both air and olivine. And finally, the extremely oxygen-sensitive pyrogallol solution was used as a colour indicator for residual oxygen in the WDA. The simulation facility in our laboratory currently consists of eight identical WDAs and a surrounding infrastructure. It can be made available to others who wish to perform cyclic wet-dry experiments.