16:10 〜 16:30
[BBG01-07] Extraterrestrial Nucleobases Are More Abundant Than Previously Thought: Potential Links of the Distributions of N-heterocycles with Meteorite Minerals
★Invited Papers
キーワード：核酸塩基、炭素質隕石、高速液体クロマトグラフィー高分解能質量分析、化学進化
Extraterrestrial organic molecules were formed through a diverse array of chemical reactions that took place during the solar system's formation. These reactions include interactions with minerals and water within the meteorite and asteroid parent bodies. Nucleobases, crucial components of nucleic acids, have been robustly identified in carbonaceous meteorites over the past two decades, stimulating intense interest in the origins of life's building blocks within the solar system [1, 2]. Utilizing advanced analytical techniques capable of detecting nucleobases at the femto-mole level, our study identified the pyrimidine nucleobase uracil in samples from the carbonaceous asteroid 'Ryugu (162173),' returned by the Hayabusa-2 mission [3]. These findings not only add to the growing evidence of extraterrestrial nucleobases but also prompt further investigation into their synthesis, abundance, and distribution during the solar system's formation, and their potential delivery to the early Earth. Contrary to the standardized methodologies applied in the analysis of extraterrestrial amino acids, the extraction and purification of nucleobases from meteoritic samples have varied across previous studies [1, 2]. Therefore, our research introduces refined extraction, purification, and analytical techniques to provide a more accurate assessment of extraterrestrial nucleobases' abundances and distributions [4].
Analyzing a sample from the CM2 Murchison meteorite, we employed a two-step extraction process—initially with hot water, followed by 6 M hydrochloric acid (HCl)—and purification via cation exchange chromatography. High-performance liquid chromatography coupled with electrospray ionization, high-resolution mass spectrometry (HPLC/HRMS), revealed significantly higher concentrations of purine nucleobases, including guanine and adenine, in the 6 M HCl extract (1090 ± 104 ng/g-meteorite, hereafter ng/g) compared to the hot-water extract (215 ± 3 ng/g). The total purine concentration (1305 ± 107 ng/g) markedly exceeded previously reported values by approximately nine times. In contrast, pyrimidine nucleobases, including cytosine, uracil, and thymine, were more abundant in the hot-water extract (297 ± 5 ng/g) than in the HCl extract (51 ± 4 ng/g), with the total pyrimidine concentration (348 ± 7 ng/g) being approximately eleven times higher than earlier findings. Furthermore, imidazole molecules, which are five-membered-ring N-heterocycles with high water solubility, showed a distribution pattern similar to purines. These findings suggest that the differing molecular distributions of N-heterocycles in the meteorite cannot be solely attributed to water solubility differences. Hence, the distinct distributions of purine and pyrimidine nucleobases in the Murchison meteorite indicate that purines may be more effectively incorporated into meteoritic matrices than pyrimidines. Our results may imply that interactions among organic compounds, minerals, and water might have played a crucial role in the chemical evolution of life’s building blocks in the meteorite parent body.
References: [1] Callahan et al. (2011) PNAS, 108, 13995–13998. [2] Oba et al. (2022) Nat. Commun. 13, 2008. [3] Oba et al. (2023) Nat. Commun. 14, 1292. [4] Koga et al. (2024) GCA, 355, 253–265.
Analyzing a sample from the CM2 Murchison meteorite, we employed a two-step extraction process—initially with hot water, followed by 6 M hydrochloric acid (HCl)—and purification via cation exchange chromatography. High-performance liquid chromatography coupled with electrospray ionization, high-resolution mass spectrometry (HPLC/HRMS), revealed significantly higher concentrations of purine nucleobases, including guanine and adenine, in the 6 M HCl extract (1090 ± 104 ng/g-meteorite, hereafter ng/g) compared to the hot-water extract (215 ± 3 ng/g). The total purine concentration (1305 ± 107 ng/g) markedly exceeded previously reported values by approximately nine times. In contrast, pyrimidine nucleobases, including cytosine, uracil, and thymine, were more abundant in the hot-water extract (297 ± 5 ng/g) than in the HCl extract (51 ± 4 ng/g), with the total pyrimidine concentration (348 ± 7 ng/g) being approximately eleven times higher than earlier findings. Furthermore, imidazole molecules, which are five-membered-ring N-heterocycles with high water solubility, showed a distribution pattern similar to purines. These findings suggest that the differing molecular distributions of N-heterocycles in the meteorite cannot be solely attributed to water solubility differences. Hence, the distinct distributions of purine and pyrimidine nucleobases in the Murchison meteorite indicate that purines may be more effectively incorporated into meteoritic matrices than pyrimidines. Our results may imply that interactions among organic compounds, minerals, and water might have played a crucial role in the chemical evolution of life’s building blocks in the meteorite parent body.
References: [1] Callahan et al. (2011) PNAS, 108, 13995–13998. [2] Oba et al. (2022) Nat. Commun. 13, 2008. [3] Oba et al. (2023) Nat. Commun. 14, 1292. [4] Koga et al. (2024) GCA, 355, 253–265.