11:00 〜 11:15
[U12-07] Photochemical synthesis of building blocks from a plausible CO atmosphere containing N2O
キーワード： プレバイオティクス、生命起源、アミノ酸合成、光化学
Prebiotic synthesis is known to be more favorable in a strongly reducing atmosphere (H2-CH4-NH3-N2-H2O) than a redox neutral atmosphere (CO2-N2-H2O) [1]. However, an atmosphere containing CO can yield comparable amounts of bioorganic compounds as a strongly reducing atmosphere [2], implying that CO has the ability to initial key reactions involved in prebiotic synthesis. In our previous study, a series of UV irradiation experiments demonstrated that atmospheric N2O can be largely converted into NH3 under the presence of CO [3]. Moreover, the atmospheric UV chemistry can form ammino acids from N2O and CO even without catalyst [3]. Therefore, the atmospheric UV chemistry from CO and N2O may provide an alternative pathway to form amino acids or other building blocks on early Earth. In order to investigate the UV chemistry from a plausible CO atmosphere containing N2O, we report further analysis of the experimental products systematically.
After UV irradiation to CO, N2O and H2O, first, the samples were measured using Matrix Assisted Laser Desorption Ionization time-of-flight mass spectrometer (MALDI-TOF-MS). The results showed that heterocyclic nitrogen compounds were present. Then, the samples were measure using HPLC-Orbitrap MS for cross-validation. The results identified that imidazole, HMT and its derivatives such as methyl HMT and hydroxy HMT, as well as isomers of nucleobases were synthesized. Among these products, HMT is the most abundant product. In addition, formaldehyde (HCHO), glycolaldehyde as well as glyoxal were determined. Moreover, the variety of amino acids, and the product amount of NH3, amino acids as well as glycolic acid increased largely when liquid samples were hydrolyzed by 6M HCl at 110℃ for 24 hours. Meanwhile, HMT decreased after hydrolysis, generating HCHO and NH3. Combining these results, amino acids as well as other building blocks were highly possible to be synthesized from HCHO and NH3 through formose-type reaction, instead of reaction via hydrogen cyanide (HCN) as intermediate.
Based on the experimental results, estimated production rates of glycine and NH3 were obtained. Photochemical supply of glycine from N2O in an atmosphere containing 1% of CO was calculated as 1.2×106 ~ 6.0×107 kg/yr, implicating an efficient atmospheric supply of NH3 and amino acids.
The simultaneously, efficient production of prebiotic important molecules from a plausible CO-rich primitive atmosphere containing N2O provide a novel insight in prebiotic chemistry on early Earth. And the discovery of this study expands our current acknowledge on nitrogen cycle on primitive Earth as well as planetary atmospheric chemistry.
[1] Schlesinger G., and Miller S. (1983) Prebiotic synthesis in atmospheres containing CH4, CO and CO2. Journal of molecular evolutoin, 19: 376-382.
[2] Miyakawa S., Yamanashi H., Kobayashi K., Cleaves H. J., and Miller S. L. (2002) Prebiotic synthesis from CO atmospheres: Implications for the origins of life. Proceedings of the National Academy of Sciences, 99: 14628-14631.
[3] Zang X., Ueno Y., and Kitadai N. (2022) Photochemical Synthesis of Ammonia and Amino Acids from Nitrous Oxide. Astrobiology, 22: 387-398.
After UV irradiation to CO, N2O and H2O, first, the samples were measured using Matrix Assisted Laser Desorption Ionization time-of-flight mass spectrometer (MALDI-TOF-MS). The results showed that heterocyclic nitrogen compounds were present. Then, the samples were measure using HPLC-Orbitrap MS for cross-validation. The results identified that imidazole, HMT and its derivatives such as methyl HMT and hydroxy HMT, as well as isomers of nucleobases were synthesized. Among these products, HMT is the most abundant product. In addition, formaldehyde (HCHO), glycolaldehyde as well as glyoxal were determined. Moreover, the variety of amino acids, and the product amount of NH3, amino acids as well as glycolic acid increased largely when liquid samples were hydrolyzed by 6M HCl at 110℃ for 24 hours. Meanwhile, HMT decreased after hydrolysis, generating HCHO and NH3. Combining these results, amino acids as well as other building blocks were highly possible to be synthesized from HCHO and NH3 through formose-type reaction, instead of reaction via hydrogen cyanide (HCN) as intermediate.
Based on the experimental results, estimated production rates of glycine and NH3 were obtained. Photochemical supply of glycine from N2O in an atmosphere containing 1% of CO was calculated as 1.2×106 ~ 6.0×107 kg/yr, implicating an efficient atmospheric supply of NH3 and amino acids.
The simultaneously, efficient production of prebiotic important molecules from a plausible CO-rich primitive atmosphere containing N2O provide a novel insight in prebiotic chemistry on early Earth. And the discovery of this study expands our current acknowledge on nitrogen cycle on primitive Earth as well as planetary atmospheric chemistry.
[1] Schlesinger G., and Miller S. (1983) Prebiotic synthesis in atmospheres containing CH4, CO and CO2. Journal of molecular evolutoin, 19: 376-382.
[2] Miyakawa S., Yamanashi H., Kobayashi K., Cleaves H. J., and Miller S. L. (2002) Prebiotic synthesis from CO atmospheres: Implications for the origins of life. Proceedings of the National Academy of Sciences, 99: 14628-14631.
[3] Zang X., Ueno Y., and Kitadai N. (2022) Photochemical Synthesis of Ammonia and Amino Acids from Nitrous Oxide. Astrobiology, 22: 387-398.