Transition metal nanoparticles: A missing link between early Earth and early life

我们提出这一建议的动机是观察到，在产生氢气的热液喷口中自然发生的化学反应与厌氧自养生物中碳和能量代谢的核心反应具有可检测的相似性，厌氧自养生物使用乙酰辅酶A途径固定CO2，将早期地球化学与原始细菌和古细菌的代谢反应联系起来。在上一个资助期的实验中，我们已经表明，在米尔海姆合成的两种天然存在的过渡金属矿物，铁镍铁矿（Ni 3Fe）和磁铁矿（Fe 3 O 4）作为纳米颗粒催化剂，将可重复地将24 bar的H2和CO2（40：60）转化为甲酸盐（约100 bar）。100 mM）、乙酸盐（ca. 100微米），和丙酮酸盐（约。40微米）在杜塞尔多夫的小型实验室反应器中在100°C下在水的存在下过夜。该高度特异性的产物谱包括从H2和CO2到丙酮酸的乙酰辅酶A途径的前三个游离中间体。虽然Ni 3Fe和Fe 3 O 4都可以实现10-酶途径的催化作用，但氮掺入氨基酸已被证明更具挑战性，需要我们探索替代的，更极端的条件。在这里，我们将研究高压和高温条件（高达380°C和800 bar）以及机械化学的能力，以产生适当活化的氮物质，用于掺入氨基酸，碱基的生化构建块。已经表明过渡金属可以特异性地催化NAD+到NADH的H2依赖性还原，我们将探索它们取代基于黄素的电子分叉的最古老和保守的功能的能力：低电位铁氧还蛋白的H2依赖性还原。如果成功的话，我们的发现将在原始自养生物的生理学和产生H2的热液喷口中自然发生的多相催化之间建立化学进化联系，从而揭示长期存在的代谢和生命如何产生的问题。

Motivation for our proposal is the observation that naturally occurring chemical reactions in H2 producing hydrothermal vents bear detectable similarity to the core reactions of carbon and energy metabolism in anaerobic autotrophs that use the acetyl-CoA pathway of CO2 fixation, linking early earth chemistry to the metabolic reactions in primitive bacteria and archaea. In experiments from the previous funding period we have shown that two naturally existing transition metal minerals, awaruite (Ni3Fe) and magnetite (Fe3O4), synthesized as nanoparticular catalysts in Mülheim, will reproducibly convert 24 bar of H2 and CO2 (40:60) to formate (ca. 100 mM), acetate (ca. 100 micrometers), and pyruvate (ca. 40 micrometers) overnight at 100°C in the presence of water in small laboratory reactors in Düsseldorf. This highly specific product spectrum comprises the first three free intermediates of the acetyl-CoA pathway from H2 and CO2 to pyruvate. Although Ni3Fe and Fe3O4 can both fulfill the catalytic role of the 10-enzyme pathway, nitrogen incorporation to amino acids has proven more challenging, requiring us to explore alternative, more extreme conditions. Here we will investigate the ability of high pressure and high temperature conditions (up to 380°C and 800 bar) as well as mechanochemistry to generate suitably activated nitrogen species for incorporation into amino acids, the biochemical building blocks of bases. Having shown that transition metals can specifically catalyze the H2 dependent reduction of NAD+ to NADH, we will explore their ability to replace the most ancient and conserved function of flavin based electron bifurcation: the H2 dependent reduction of low potential ferredoxin. If successful, our findings will forge chemical evolutionary connections between the physiology of primitive autotrophs and naturally occurring heterogeneous catalysis in H2 producing hydrothermal vents, shedding light on longstanding questions of how metabolism, and life, could have arisen.