5:15 PM - 6:30 PM
[MIS02-P05] Amino acid production by heating and gamma-ray irradiation experiments simulating aqueous alteration in small bodies
Keywords:Amino acid, Gamma-rays, aqueous alteration, carbonaceous chondrites
Amino acid production by heating and gamma-ray irradiation experiments simulating aqueous alteration in small bodies
*Akari Ishikawa1､Yoko Kebukawa1､Isao Yoda2､Kensei Kobayashi1
1.Yokohama National University､2.Tokyo Institute of Technology
[Introduction]
Organic substances such as amino acids are indispensable for the origin of life, and they have been delivered from meteorites . The meteorites containing organic matter are known as carbonaceous chondrites, and their parent bodies have been subjected to aqueous alteration mostly due to the heat generated by the radioactive decay of short-lived radionuclides such as 26Al. Macromolecular organic matter and amino acids in carbonaceous chondrites could be produced during such hydrothermal process [1] [2]. On the other hand, the gamma rays from the decay of 26Al might directly contributes to the formation of amino acids. The previous studies shown that gamma rays contributed to form various amino acids from HCHO and NH3 aqueous solutions[3]. In this study, we investigated the effects of gamma rays for the production of amino acids from various starting solutions containing simple molecules likely excited in the small bodies such as HCHO, NH3, glycolaldehyde, hexamethylenetetramine (HMT), and compared with the effects of heating.
[Experiment]
The following mixed solutions were prepared as a starting materials.
(1) HCHO : Glycolaldehyde : NH3 : Ca(OH)2 : H2O = 3.60 : 1.80 : 0.72 : 0.36 : 100 (molar ratio)
(2) HMT : H2O = 1 : 100
(3) HCHO : NH3 : H2O = 5 : 5 : 100
Each 200 μL solution was vacuum-sealed in a glass tube. The samples were heated (24, 48, 72 h at 150 ℃) or subjected to gamma-ray irradiation (0.5, 1.5 kGy/h for 5, 20 h) from a 60Co source at Tokyo Institute of Technology. The experimental products were acid hydrolyzed with 6 M hydrochloric acid (24 h at 110 ℃), and then analyzed by cation exchange HPLC for amino acid concentrations.
[Results and Discussion]
The amino acids in the samples (1) to (3) were mainly glycine (Gly), alanine (Ala), and β-alanine (β-Ala). In addition, serine (Ser), leucine (Leu), β-aminoisobutyric acid (β-AiBA), etc. were detected. The total concentrations of amino acids as well as variations in the amino acids were highest in the sample (3) after both heating and gamma-ray irradiation. In the case of gamma-ray irradiation, the number of detected amino acids in the sample (2) was higher than (1), and in the case of heating, the number of detected amino acids in the sample (2) was lower than (1). In addition, the total concentration of amino acids in the sample (1) was higher than (2) for both gamma-ray irradiated samples and heated samples.
Comparing the heated samples and the gamma-ray irradiated samples, the gamma-ray irradiated sample had larger variations than the heated samples in the case of (1) and (3). The amino acids concentrations were larger in the samples after longer heating, but their concentrations did not show significant correlation with gamma-ray dose.
The lower concentrations of amino acids in the sample (2) was probably due to partial decomposition of HMT[4]. The amino acid concentrations in sample (1) was small likely because the initial concentration of NH3 was small compared to HCHO and glycolaldehyde. In addition, macromolecular compounds other than amino acids could be produced in the sample (1).
[Conclusions]
The amino acids were detected from all of the heated samples and gamma-ray irradiated samples after acid hydrolysis. The largest amounts of amino acids were produced from the sample (3). The gamma-ray induced larger variations in the amino acids than heating, but the amino acid productions did not show significant correlation with gamma-ray dose.
[References]
[1] G. D. Cody et al., PNAS 2011, 108, 19171-16.
[2] Y. Kebukawa et al., Sci. Adv. 2017, 3, e1602093.
[3] Y. Kebukawa et al., 81st Annual Meeting of The Meteoritical Society, 2018, LPI Contribution No. 2067.
[4] V. Vinogradoff et al., ACS Earth Space Chem. 2020, 4, 1398-1407.
*Akari Ishikawa1､Yoko Kebukawa1､Isao Yoda2､Kensei Kobayashi1
1.Yokohama National University､2.Tokyo Institute of Technology
[Introduction]
Organic substances such as amino acids are indispensable for the origin of life, and they have been delivered from meteorites . The meteorites containing organic matter are known as carbonaceous chondrites, and their parent bodies have been subjected to aqueous alteration mostly due to the heat generated by the radioactive decay of short-lived radionuclides such as 26Al. Macromolecular organic matter and amino acids in carbonaceous chondrites could be produced during such hydrothermal process [1] [2]. On the other hand, the gamma rays from the decay of 26Al might directly contributes to the formation of amino acids. The previous studies shown that gamma rays contributed to form various amino acids from HCHO and NH3 aqueous solutions[3]. In this study, we investigated the effects of gamma rays for the production of amino acids from various starting solutions containing simple molecules likely excited in the small bodies such as HCHO, NH3, glycolaldehyde, hexamethylenetetramine (HMT), and compared with the effects of heating.
[Experiment]
The following mixed solutions were prepared as a starting materials.
(1) HCHO : Glycolaldehyde : NH3 : Ca(OH)2 : H2O = 3.60 : 1.80 : 0.72 : 0.36 : 100 (molar ratio)
(2) HMT : H2O = 1 : 100
(3) HCHO : NH3 : H2O = 5 : 5 : 100
Each 200 μL solution was vacuum-sealed in a glass tube. The samples were heated (24, 48, 72 h at 150 ℃) or subjected to gamma-ray irradiation (0.5, 1.5 kGy/h for 5, 20 h) from a 60Co source at Tokyo Institute of Technology. The experimental products were acid hydrolyzed with 6 M hydrochloric acid (24 h at 110 ℃), and then analyzed by cation exchange HPLC for amino acid concentrations.
[Results and Discussion]
The amino acids in the samples (1) to (3) were mainly glycine (Gly), alanine (Ala), and β-alanine (β-Ala). In addition, serine (Ser), leucine (Leu), β-aminoisobutyric acid (β-AiBA), etc. were detected. The total concentrations of amino acids as well as variations in the amino acids were highest in the sample (3) after both heating and gamma-ray irradiation. In the case of gamma-ray irradiation, the number of detected amino acids in the sample (2) was higher than (1), and in the case of heating, the number of detected amino acids in the sample (2) was lower than (1). In addition, the total concentration of amino acids in the sample (1) was higher than (2) for both gamma-ray irradiated samples and heated samples.
Comparing the heated samples and the gamma-ray irradiated samples, the gamma-ray irradiated sample had larger variations than the heated samples in the case of (1) and (3). The amino acids concentrations were larger in the samples after longer heating, but their concentrations did not show significant correlation with gamma-ray dose.
The lower concentrations of amino acids in the sample (2) was probably due to partial decomposition of HMT[4]. The amino acid concentrations in sample (1) was small likely because the initial concentration of NH3 was small compared to HCHO and glycolaldehyde. In addition, macromolecular compounds other than amino acids could be produced in the sample (1).
[Conclusions]
The amino acids were detected from all of the heated samples and gamma-ray irradiated samples after acid hydrolysis. The largest amounts of amino acids were produced from the sample (3). The gamma-ray induced larger variations in the amino acids than heating, but the amino acid productions did not show significant correlation with gamma-ray dose.
[References]
[1] G. D. Cody et al., PNAS 2011, 108, 19171-16.
[2] Y. Kebukawa et al., Sci. Adv. 2017, 3, e1602093.
[3] Y. Kebukawa et al., 81st Annual Meeting of The Meteoritical Society, 2018, LPI Contribution No. 2067.
[4] V. Vinogradoff et al., ACS Earth Space Chem. 2020, 4, 1398-1407.