Amino acid compositions in heated carbonaceous chondrites and their compound-specific nitrogen isotopic ratios
Amino acid compositions in heated carbonaceous chondrites and their compound-specific nitrogen isotopic ratios
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DOI：
10.1186/s40623-016-0382-8
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发表时间：
2016-01-21
影响因子：
3
通讯作者：
Ohkouchi, Naohiko
中科院分区：
文献类型：
--
作者：
Chan, Queenie Hoi Shan;Chikaraishi, Yoshito;Ohkouchi, Naohiko
已经开发出一种使用非手性色谱柱检测化合物特异性氮同位素组合物的新方法，该方法先前已被证明可以为氮同位素分析提供高精度。我们应用该方法利用气体测定了热变质（高于 500 摄氏度）南极碳质球粒陨石 Ivuna-like (CI) 1（或 CI-like）Yamato (Y) 980115 和 Ornans-like (CO) 3.5 Allan Hills (ALH) A77003 的氨基酸含量和单个氨基酸的稳定氮同位素组成。色谱法/燃烧法/同位素比质谱法。 ALHA77003 由于其较长的热变化历史而被剥夺了氨基酸。 Y-980115 中的氨基酸得到明确鉴定，所选氨基酸的 delta N-15 值（甘氨酸 +144.8%；α-丙氨酸 +121.2%）显然是外星氨基酸。 Y-980115 经历了长时间的水蚀变，如含水矿物相的存在所示。它还经历了至少一次水合后短暂的热变质作用。甘氨酸和丙氨酸可能是在小行星母体吸积事件后不久在广泛的水蚀变事件过程中产生的，并且由于母体成分和孔隙率的异质性而避免了短期的水蚀变后加热。这些碳质球粒陨石样本是很好的类似物，为了解 Hayabusa-2 任务的目标小行星 Ryugu 提供了重要的见解，Ryugu 是一颗 C 型小行星，可能由包括水合和脱水矿物在内的异质材料组成。
A novel method has been developed for compound-specific nitrogen isotope compositions with an achiral column which was previously shown to offer high precision for nitrogen isotopic analysis. We applied the method to determine the amino acid contents and stable nitrogen isotopic compositions of individual amino acids from the thermally metamorphosed (above 500 degrees C) Antarctic carbonaceous chondrites Ivuna-like (CI) 1 (or CI-like) Yamato (Y) 980115 and Ornans-like (CO) 3.5 Allan Hills (ALH) A77003 with the use of gas chromatography/combustion/isotope ratio mass spectrometry. ALHA77003 was deprived of amino acids due to its extended thermal alteration history. Amino acids were unambiguously identified in Y-980115, and the delta N-15 values of selected amino acids (glycine +144.8 %; alpha-alanine + 121.2%) are clearly extraterrestrial. Y-980115 has experienced an extended period of aqueous alteration as indicated by the presence of hydrous mineral phases. It has also been exposed to at least one post-hydration short-lived thermal metamorphism. Glycine and alanine were possibly produced shortly after the accretion event of the asteroid parent body during the course of an extensive aqueous alteration event and have abstained from the short-term post-aqueous alteration heating due to the heterogeneity of the parent body composition and porosity. These carbonaceous chondrite samples are good analogs that offer important insights into the target asteroid Ryugu of the Hayabusa-2 mission, which is a C-type asteroid likely composed of heterogeneous materials including hydrated and dehydrated minerals.