Institute of Low Temperature Science (ILTS), Hokkaido University, N19W8, Kita-ku, Sapporo, Hokkaido, 060-0189, Japan.
Biogeochemistry Research Center (BGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka, Kanagawa, 237-0061, Japan.
Nat Commun. 2022 Apr 26;13(1):2008. doi: 10.1038/s41467-022-29612-x.
The lack of pyrimidine diversity in meteorites remains a mystery since prebiotic chemical models and laboratory experiments have predicted that these compounds can also be produced from chemical precursors found in meteorites. Here we report the detection of nucleobases in three carbonaceous meteorites using state-of-the-art analytical techniques optimized for small-scale quantification of nucleobases down to the range of parts per trillion (ppt). In addition to previously detected purine nucleobases in meteorites such as guanine and adenine, we identify various pyrimidine nucleobases such as cytosine, uracil, and thymine, and their structural isomers such as isocytosine, imidazole-4-carboxylic acid, and 6-methyluracil, respectively. Given the similarity in the molecular distribution of pyrimidines in meteorites and those in photon-processed interstellar ice analogues, some of these derivatives could have been generated by photochemical reactions prevailing in the interstellar medium and later incorporated into asteroids during solar system formation. This study demonstrates that a diversity of meteoritic nucleobases could serve as building blocks of DNA and RNA on the early Earth.
陨石中嘧啶的多样性缺失仍然是一个谜，因为前生物化学模型和实验室实验预测，这些化合物也可以从陨石中发现的化学前体中产生。在这里，我们使用最先进的分析技术在三个碳质陨石中检测到了核苷，该技术经过优化，可在万亿分之几（ppt）的范围内对核苷进行小范围定量。除了先前在陨石中检测到的嘌呤核苷碱基，如鸟嘌呤和腺嘌呤，我们还分别鉴定了各种嘧啶核苷碱基，如胞嘧啶、尿嘧啶和胸腺嘧啶，以及它们的结构异构体，如异胞嘧啶、咪唑-4-羧酸和 6-甲基尿嘧啶。鉴于陨石中嘧啶的分子分布与星际冰类似物中经过光子处理的嘧啶的分子分布相似，其中一些衍生物可能是由星际介质中普遍存在的光化学反应生成的，然后在太阳系形成过程中被纳入小行星。这项研究表明，多样化的陨石核苷碱基可以作为早期地球上 DNA 和 RNA 的构建模块。
