A propensity for n-ω-amino acids in thermally altered Antarctic meteorites
A propensity for n-ω-amino acids in thermally altered Antarctic meteorites
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DOI：
10.1111/j.1945-5100.2012.01341.x
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发表时间：
2012-03-01
影响因子：
2.2
通讯作者：
Dworkin, Jason P.
中科院分区：
文献类型：
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作者：
Burton, Aaron S.;Elsila, Jamie E.;Dworkin, Jason P.
小行星及其碎片在过去的4.5 Gyr中撞击了地球。已知碳质陨石含有丰富的原生有机分子，包括氨基酸，这表明这些陨石可能是地球上生命起源期间的重要生物有机物质来源，也可能是其他地方。我们报告了从南极洲回收的热蚀变的3型CV和CO碳质方解石和ureilites中检测到的外星氨基酸。13颗南极陨石的氨基酸浓度范围为300至3200 ppb，通常比富含氨基酸的CI、CM和CR碳质陨石少得多，这些陨石在其母体上经历了低得多的温度水蚀变。与主要由Streckercyanohydrin合成形成的氨基酸显示完整结构多样性的低温水蚀变陨石相反，这里研究的热蚀变陨石主要由小的直链胺末端（n-？-氨基）氨基酸与Strecker形成不一致。两个外星n-？-的碳同位素比在一个CV样品中测量的氨基酸（d13 C约为千分之-25）与先前在通过费-托型反应产生的烃中观察到的13 C消耗一致。N-的优势？-热蚀变陨石中的氨基酸异构体暗示了一小部分可能的氨基酸优先形成和保存的宇宙化学机制。
Asteroids and their fragments have impacted the Earth for the last 4.5 Gyr. Carbonaceous meteorites are known to contain a wealth of indigenous organic molecules, including amino acids, which suggests that these meteorites could have been an important source of prebiotic organic material during the origins of life on Earth and possibly elsewhere. We report the detection of extraterrestrial amino acids in thermally altered type 3 CV and CO carbonaceous chondrites and ureilites recovered from Antarctica. The amino acid concentrations of the thirteen Antarctic meteorites ranged from 300 to 3200 parts-per-billion (ppb), generally much less abundant than in amino acid-rich CI, CM, and CR carbonaceous chondrites that experienced much lower temperature aqueous alteration on their parent bodies. In contrast to low-temperature aqueously altered meteorites that show complete structural diversity in amino acids formed predominantly by Streckercyanohydrin synthesis, the thermally altered meteorites studied here are dominated by small, straight-chain, amine terminal (n-?-amino) amino acids that are not consistent with Strecker formation. The carbon isotopic ratios of two extraterrestrial n-?-amino acids measured in one of the CV chondrites (d13C approximately -25 parts per thousand) are consistent with 13C-depletions observed previously in hydrocarbons produced by Fischer-Tropsch type reactions. The predominance of n-?-amino acid isomers in thermally altered meteorites hints at cosmochemical mechanisms for the preferential formation and preservation of a small subset of the possible amino acids.