Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases
Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases
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DOI：
10.1073/pnas.1106493108
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发表时间：
2011-08-23
影响因子：
11.1
通讯作者：
Dworkin, Jason P.
中科院分区：
文献类型：
--
作者：
Callahan, Michael P.;Smith, Karen E.;Dworkin, Jason P.
所有陆地生物都依赖核酸（RNA和DNA），核酸利用嘧啶和嘌呤碱基来编码遗传信息。富碳陨石可能是地球早期生命出现所需有机化合物的重要来源；然而，陨石中碱基的起源和形成已经争论了50多年。到目前为止，在陨石中发现的少数碱基在生物学上是常见的，缺乏其他本土陨石有机物所具有的典型结构多样性。在这里，我们通过液相色谱 - 质谱法研究了12种不同陨石的甲酸提取物中碱基和碱基类似物的丰度和分布。默奇森陨石和朗沃夫努纳塔克94102陨石含有多种碱基，其中包括三种不寻常且在地球上罕见的碱基类似物：嘌呤、2,6 - 二氨基嘌呤和6,8 - 二氨基嘌呤。在一个平行实验中，我们发现氰化铵反应产生了一组相同的碱基和碱基类似物。此外，在任何程序空白、对照样品、陆地土壤样品和南极冰样中，这些碱基类似物都未在我们十亿分之一的检测限以上被检测到。我们的结果表明，在陨石中检测到的嘌呤与氰化铵化学产物一致，这为它们在小行星母体中的合成提供了一个合理的机制，并有力地支持了其地外起源。在陨石中发现新的碱基类似物也扩充了可用于构建首批遗传分子的前生物分子库。
All terrestrial organisms depend on nucleic acids (RNA and DNA), which use pyrimidine and purine nucleobases to encode genetic information. Carbon-rich meteorites may have been important sources of organic compounds required for the emergence of life on the early Earth; however, the origin and formation of nucleobases in meteorites has been debated for over 50 y. So far, the few nucleobases reported in meteorites are biologically common and lacked the structural diversity typical of other indigenous meteoritic organics. Here, we investigated the abundance and distribution of nucleobases and nucleobase analogs in formic acid extracts of 12 different meteorites by liquid chromatography-mass spectrometry. The Murchison and Lonewolf Nunataks 94102 meteorites contained a diverse suite of nucleobases, which included three unusual and terrestrially rare nucleobase analogs: purine, 2,6-diaminopurine, and 6,8-diaminopurine. In a parallel experiment, we found an identical suite of nucleobases and nucleobase analogs generated in reactions of ammonium cyanide. Additionally, these nucleobase analogs were not detected above our parts-per-billion detection limits in any of the procedural blanks, control samples, a terrestrial soil sample, and an Antarctic ice sample. Our results demonstrate that the purines detected in meteorites are consistent with products of ammonium cyanide chemistry, which provides a plausible mechanism for their synthesis in the asteroid parent bodies, and strongly supports an extraterrestrial origin. The discovery of new nucleobase analogs in meteorites also expands the prebiotic molecular inventory available for constructing the first genetic molecules.