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英国利兹大学（University of Leeds）的一项最新研究发现，地球生命诞生过程中的“原始能量”物质，其由磷元素参与形成，被认为是无机环境与第一个生物细胞出现的中间步骤。
研究人员称可能揭开了地球上生命诞生过程的一个关键难题，目前生命诞生理论普遍认为是陨石将生命种子带到地球上，但是科学家们一直无法解释这些“没有生命”的物质是如何转化成“生命”的，最新的研究认为这一过程中出现了一种类似ATP的能量物质，含磷矿物陨石坠落在遍布地球的酸性液体环境中，形成了原始的、可供生命使用的能量源。
地球生命的出现似乎带有“凭空出现”般的惊艳，科学家一直探索生命是如何走出死气沉沉的无机环境，对此利兹大学化学院特里·基博士认为我们发现了不寻常的磷化合物，其可能是生物细胞直接能源的原始版本，该物质的出现可能将地质学与生物学之间的缺失环节联系在了一起，使得早期地球具备了可被细胞利用的能量。众所周知，目前地球生物细胞的直接能源为三磷酸腺苷，也称为ATP，在细胞呼吸作用中扮演着重要的角色。科学家希望找到一个类似ATP的原始物质，但是这种物质并不需要酶的介入。
磷不仅是ATP合成的关键元素，也是细胞DNA序列的基本模块，科学家通过模拟早期地球的恶劣环境，比如火山活动、大气成分等，并将取自西伯利亚的陨石放置在这样的环境中观察其变化，实验结果发现在与酸性流质等反应后，产生出ATP分子的早期形式，研究人员将其称为无机环境与第一个生物细胞诞生的中间步骤，这种原始的能量物质就像原始的电池。
NASA的好奇号火星车也将磷元素列入探索的目标，现在已经证实火星上存在磷，如果好奇号也发现类似的磷化合物，那么这可能表明火星环境的确适合生命的诞生，至少演化步骤与早期地球类似。此外，研究人员还希望前往格陵兰岛寻找可能存在类似化学物质的陨石，通过重复性实验模拟出地球生命诞生的过程。
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Hydrothermal modification of the Sikhote-Alin iron meteorite under low pH geothermal environments. A plausibly prebiotic route to activated phosphorus on the early Earth
Geochimica et Cosmochimica Acta, 15 May 2013 | doi.org/10.1016/j.gca.2012.12.043
The Sikhote-Alin (SA) meteorite is an example of a type IIAB octahedrite iron meteorite with ca. 0.5 wt% phosphorus (P) content principally in the form of the siderophilic mineral schreibersite (Fe,Ni)3P. Meteoritic in-fall to the early Earth would have added significantly to the inventory of such siderophilic P. Subsequent anaerobic corrosion in the presence of a suitable electrolyte would produce P in a form different to that normally found within endogenous geochemistry which could then be released into the environment. One environment of specific interest includes the low pH conditions found in fumaroles or volcanically heated geothermal waters in which anodic oxidation of Fe metal to ferrous (Fe2+) and ferric (Fe3+) would be coupled with cathodic reduction of a suitable electron acceptor. In the absence of aerobic dioxygen (Eo = +1.229 V), the proton would provide an effective final electron acceptor, being converted to dihydrogen gas (Eo = 0 V). Here we explore the hydrothermal modification of sectioned samples of the Sikhote-Alin meteorite in which siderophilic P-phases are exposed. We report on both, (i) simulated volcanic conditions using low pH distilled water and (ii) geothermally heated sub-glacial fluids from the northern Kverkfjöll volcanic region of the Icelandic Vatnajoküll glacier. A combination of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements using the scanning Kelvin probe (SKP) method reveals that schreibersite inclusions are significantly less susceptible to anodic oxidation than their surrounding Fe–Ni matrix, being some 550 mV nobler than matrix material. This results in preferential corrosion of the matrix at the matrix-inclusion boundary as confirmed using topological mapping via infinite focus microscopy and chemical mapping through Raman spectroscopy. The significance of these observations from a chemical perspective is that electrochemically noble inclusions such as schreibersite are likely to have been released into the geological environment through an undermining corrosion of the surrounding matrix, thus affording localised sources of available water-soluble, chemically reactive P in the form of H-phosphite [
, Pi(III) as determined by31P NMR spectroscopy]. This compound has been shown to have considerable prebiotic chemical potential as a source of condensed P-oxyacids. Here we demonstrate that Pi(III) resulting from the hydrothermal modification of Sikhote-Alin by sub-glacial geothermal fluids can be readily dehydrated into the condensed P-oxyacid pyrophosphite [
, PPi(III)] by dry-heating under mild (85 °C) conditions. The potential significance of this latter condensed P-compound for prebiotic chemistry is discussed in the light of its modified chemical properties compared to pyrophosphate [
, PPi(V)].
发表于 2013-4-8 09:15
