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[MIS02-P06] Abiotic synthesis of sugars by heating or gamma irradiation simulating aqueous alteration in meteorite parent bodies
Keywords:Sugars, Formose reaction
1.Introduction
Sugars and sugar derivatives play important roles in biological processes on the Earth. Sugars such as ribose, a component of RNA, are essential compounds for the origin of life. Since some sugars have been found in meteorites [1, 2], there is a possibility that some extraterrestrial sugar brought to the early Earth by carbonaceous meteorites. As a prebiotic sugar formation reaction, the “formose reaction” have been attracted attention [1, 2]. The formose reaction is the reaction that makes various sugars from aldehydes by using base catalysts, and further reaction makes substances whose structure is like Insoluble Organic Matter (IOM) in meteorites [3]. It is also known that amino acids are made with IOM-like substances by adding ammonia to aldehydes [4].
Meteorite parent bodies are considered to be among the places where the formose reaction may have occurred, since (i) formaldehyde, which is the raw material of the formose reaction, was likely to be present in there, and (ii) hydrothermal alteration induced by the radioactive decay heat from 26Al presented in meteorite parent bodies might have promoted the formose reaction.
The effects of heat have been mainly investigated of formation of organic matter by the formose reaction. However, since the heat source is radionuclides such as 26Al, it is possible that radiation such as γ-ray affected the formation of bio-related substances [5]. In this research, we verified whether sugars were formed or not in products by the “formose-like reaction” using heat or γ-ray simulating aqueous alteration in meteorite parent bodies, and we compared the results by these two energies.
2.Experimental
In this research, we applied aldononitrile acetate ester derivatization method [6] to GC/MS analysis of sugars and their related compounds. In this method, the aldehyde group of the sugar was reduced to nitrile group with hydrochloride hydroxylamine, and then the hydroxy group was converted to acetate ester with acetic anhydride.
Standard reagents of aldose (C3 : glyceraldehyde, C4 : erythrose, threose, C5 : ribose, lyxose, arabinose, xylose, C6 : allose, talose, mannose, altrose, glucose, gulose, idose, galactose) were derivatized by the aldononitrile acetate ester derivatization.
In order to simulate reactions in the meteorite parent bodies, 6 kinds of the starting mixtures were prepared: (1) formaldehyde : H2O = 10 : 100, (2) glycolaldehyde : glyceraldehyde = 10 : 100, (3) formaldehyde : glycolaldehyde : H2O = 3.6 : 1.8 : 100 (figures show the molar ratio of compounds of each system) and (1)-(3) with calcium hydroxide as a catalyst were prepared. 200 µL of each mixture was heated at 150℃ for 3 days or irradiated by γ-ray (60Co source at Tokyo Institute of Technology, 1.5 kGy/h) for 20 hours. An aliquot of each product was derivatized by the present method, and analyzed by GC/MS.
3.Results and Discussion
Retention time and major m/z of each aldose were obtained by using authentic standards: The retention times (major m/z’s) were as follows. Triose: 9.7 min (m/z 86, 103), tetroses: 17.7-18.0 min (m/z 103, 145), pentoses: 24.8-26.0 min (m/z 103, 115, 145) and hexoses: 31.0-33.0 min (m/z 103, 115, 145). There was a positive correlation between the carbon number and the retention time.
By comparing the analysis results of aldose standard reagents and the products of the “formose-like reaction” simulating the interior of meteorite parent bodies, peaks similar to those of pentoses were detected in all the products, and peaks similar to those of tetroses and hexoses were detected in most of γ-ray irradiated products and some heated products. On the whole, hexoses tended to be harder to produce than tetroses and pentoses.
In the same system, varieties and amounts of aldose produced by γ-ray irradiation tended to be greater than those of heated samples. Therefore, the pathway of aldose formation by γ-ray irradiation might differ from the formose-like reaction caused by heating.
Referring to the effects of calcium hydroxide catalyst, some samples with the catalyst produced more aldoses than without it, but other products showed opposite result. It was suggested that the catalyst promote not only producing aldoses but also further reactions that converted aldose into larger molecules.
4.References
[1] G. Cooper et al. (2001) Nature, 414, 879-883.
[2] Y. Furukawa et al. (2019) PNAS, 116, 24440-24445.
[3] G. D. Cody et al. (2011) PNAS, 108, 19171-19176.
[4] Y. Kebukawa et al. (2017) Science Advances, 3, e1602093.
[5] Y. Kebukawa et al. (2018) 81st Annual Meeting of The Meteoritical Society, LPI Contribution No. 2067.
[6] K. Kobayashi et al. (1989) Bunseki Kagaku, 38, 608-612.
Sugars and sugar derivatives play important roles in biological processes on the Earth. Sugars such as ribose, a component of RNA, are essential compounds for the origin of life. Since some sugars have been found in meteorites [1, 2], there is a possibility that some extraterrestrial sugar brought to the early Earth by carbonaceous meteorites. As a prebiotic sugar formation reaction, the “formose reaction” have been attracted attention [1, 2]. The formose reaction is the reaction that makes various sugars from aldehydes by using base catalysts, and further reaction makes substances whose structure is like Insoluble Organic Matter (IOM) in meteorites [3]. It is also known that amino acids are made with IOM-like substances by adding ammonia to aldehydes [4].
Meteorite parent bodies are considered to be among the places where the formose reaction may have occurred, since (i) formaldehyde, which is the raw material of the formose reaction, was likely to be present in there, and (ii) hydrothermal alteration induced by the radioactive decay heat from 26Al presented in meteorite parent bodies might have promoted the formose reaction.
The effects of heat have been mainly investigated of formation of organic matter by the formose reaction. However, since the heat source is radionuclides such as 26Al, it is possible that radiation such as γ-ray affected the formation of bio-related substances [5]. In this research, we verified whether sugars were formed or not in products by the “formose-like reaction” using heat or γ-ray simulating aqueous alteration in meteorite parent bodies, and we compared the results by these two energies.
2.Experimental
In this research, we applied aldononitrile acetate ester derivatization method [6] to GC/MS analysis of sugars and their related compounds. In this method, the aldehyde group of the sugar was reduced to nitrile group with hydrochloride hydroxylamine, and then the hydroxy group was converted to acetate ester with acetic anhydride.
Standard reagents of aldose (C3 : glyceraldehyde, C4 : erythrose, threose, C5 : ribose, lyxose, arabinose, xylose, C6 : allose, talose, mannose, altrose, glucose, gulose, idose, galactose) were derivatized by the aldononitrile acetate ester derivatization.
In order to simulate reactions in the meteorite parent bodies, 6 kinds of the starting mixtures were prepared: (1) formaldehyde : H2O = 10 : 100, (2) glycolaldehyde : glyceraldehyde = 10 : 100, (3) formaldehyde : glycolaldehyde : H2O = 3.6 : 1.8 : 100 (figures show the molar ratio of compounds of each system) and (1)-(3) with calcium hydroxide as a catalyst were prepared. 200 µL of each mixture was heated at 150℃ for 3 days or irradiated by γ-ray (60Co source at Tokyo Institute of Technology, 1.5 kGy/h) for 20 hours. An aliquot of each product was derivatized by the present method, and analyzed by GC/MS.
3.Results and Discussion
Retention time and major m/z of each aldose were obtained by using authentic standards: The retention times (major m/z’s) were as follows. Triose: 9.7 min (m/z 86, 103), tetroses: 17.7-18.0 min (m/z 103, 145), pentoses: 24.8-26.0 min (m/z 103, 115, 145) and hexoses: 31.0-33.0 min (m/z 103, 115, 145). There was a positive correlation between the carbon number and the retention time.
By comparing the analysis results of aldose standard reagents and the products of the “formose-like reaction” simulating the interior of meteorite parent bodies, peaks similar to those of pentoses were detected in all the products, and peaks similar to those of tetroses and hexoses were detected in most of γ-ray irradiated products and some heated products. On the whole, hexoses tended to be harder to produce than tetroses and pentoses.
In the same system, varieties and amounts of aldose produced by γ-ray irradiation tended to be greater than those of heated samples. Therefore, the pathway of aldose formation by γ-ray irradiation might differ from the formose-like reaction caused by heating.
Referring to the effects of calcium hydroxide catalyst, some samples with the catalyst produced more aldoses than without it, but other products showed opposite result. It was suggested that the catalyst promote not only producing aldoses but also further reactions that converted aldose into larger molecules.
4.References
[1] G. Cooper et al. (2001) Nature, 414, 879-883.
[2] Y. Furukawa et al. (2019) PNAS, 116, 24440-24445.
[3] G. D. Cody et al. (2011) PNAS, 108, 19171-19176.
[4] Y. Kebukawa et al. (2017) Science Advances, 3, e1602093.
[5] Y. Kebukawa et al. (2018) 81st Annual Meeting of The Meteoritical Society, LPI Contribution No. 2067.
[6] K. Kobayashi et al. (1989) Bunseki Kagaku, 38, 608-612.