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[PPS08-08] Formation of sugars by formose-type reaction simulating aqueous alteration in a meteorite parent bodies - Effects of gamma-rays and starting materials -
Keywords:Sugars, Formose reaction, Gamma-rays
Introduction
Sugars have been found in some meteorites along with amino acids and nucleobases [1,2]. One of the major abiotic sugar formation reactions is the formose reaction, in which sugars are produced from formaldehydes under basic condition. It was known that similar reaction (formose-type reaction) simulating the aqueous alteration in meteorite parent bodies made amino acids by adding ammonia to the starting materials [3,4]. Ammonia increased the formation rate of sugars [5]; on the other hand, it has been suggested that the formation of sugars was inhibited by nitrogen-containing compounds in experiments by spark discharge in a simulated primordial atmosphere [6]. Meteorite parent bodies are considered to be one of the possible production sites of sugars in space [2]. Aldehydes were speculated to be present here, and formose-type reactions may have occurred with the aqueous alteration caused by the radioactive decay such as 26Al. Previous study has suggested that gamma-rays were effective on the formation of amino acids by simulating aqueous alteration in a meteorite parent bodies [7].In this study, we compared the yields of aldoses in the products by heating or gamma-rays irradiation in a system simulating the aqueous alteration in meteorite parent bodies in order to investigate the effects of gamma-rays on the formation of sugars (aldoses). To verify the effects of ammonia on the formation of sugars, we conducted gamma-rays irradiation experiments with various fractions of ammonia in the starting solutions.
Experimental
To simulate aqueous alteration inside the meteoric parent bodies, the following solutions (200 μL) were prepared whose compositions were: (1) HCHO : CH3OH : NH3 : H2O = 5:0.83:x:100 (the mixture was called FAW), (2) HCHO : CH3OH : NH3 : glycolaldehyde (GA) : H2O = 5:0.83:x:1:100 (the mixture was called FAGW) were prepared. Here, x was varied as (1) x=0, 0.5, 1, 2, 3, 4, 5, (2) x=0, 1, 5. CH3OH was added as a stabilizer for formaldehyde reagent. These samples were heated (50 ℃, 72 h) or gamma-rays irradiated (60Co source, 1.5 kGy/h, 60 h) and analyzed by gas chromatography mass spectrometry (GC/MS) after aldononitrile acetate ester derivatization [6]. We analyzed 3-6 carbons aldoses.
Results and Discussions
[Comparison of heating and gamma-rays irradiation]
In FAW, amounts and varieties of aldoses produced by gamma-rays irradiation tended to be greater than those of heated samples. On the other hand, FAGW produced the same amounts and varieties of aldoses by both energy sources. These results suggest that in the γ-rays irradiated FAW samples, GA was produced by a radical reaction [8], which facilitated the formose-type reactions and increased the production of sugars.
[Effects of starting materials]
The large amounts of aldoses obtained with FAGW suggests that the presence of GA is important for the formation of sugars. As for the effects of ammonia, the largest amounts of aldoses were produced when NH3/HCHO = 0.1-0.2, and the amounts of aldoses decreased as the amount of ammonia increased. These results suggest that ammonia has two functions: to catalyze reactions and to inhibit the formation of aldoses or to convert the generated sugars to other substances.
Summary
The presence of GA is important for the formation of sugars. The formation of GA from HCHO by gamma-rays suggests that gamma-rays also promoted sugar formation in the meteorite parent bodies. Ammonia was shown to both promote and inhibit the formation of sugars in formose-type reactions.
References
[1] Y. Furukawa et al., PNAS, 2019, 116, 24440-24445.
[2] G. Cooper et al., Nature, 2001, 414, 879-883.
[3] T. Koga et al., Scientific reports, 2017, 7, 636.
[4] Y. Kebukawa et al., Science Advances, 2017, 3, e1602093.
[5] AL.Weber, Orig. Life Evol. Biosph., 2001, 31, 71-86.
[6] K. Kobayashi et al., Bunseki Kagaku, 1989, 38, 608-612.
[7] Y. Kebukawa et al., ACS Cent. Sci., 2022, 8, 1664-1671.
[8] A. López-Islas et al., Int. J. Astrobiol., 2018, 18, 420-425.
Sugars have been found in some meteorites along with amino acids and nucleobases [1,2]. One of the major abiotic sugar formation reactions is the formose reaction, in which sugars are produced from formaldehydes under basic condition. It was known that similar reaction (formose-type reaction) simulating the aqueous alteration in meteorite parent bodies made amino acids by adding ammonia to the starting materials [3,4]. Ammonia increased the formation rate of sugars [5]; on the other hand, it has been suggested that the formation of sugars was inhibited by nitrogen-containing compounds in experiments by spark discharge in a simulated primordial atmosphere [6]. Meteorite parent bodies are considered to be one of the possible production sites of sugars in space [2]. Aldehydes were speculated to be present here, and formose-type reactions may have occurred with the aqueous alteration caused by the radioactive decay such as 26Al. Previous study has suggested that gamma-rays were effective on the formation of amino acids by simulating aqueous alteration in a meteorite parent bodies [7].In this study, we compared the yields of aldoses in the products by heating or gamma-rays irradiation in a system simulating the aqueous alteration in meteorite parent bodies in order to investigate the effects of gamma-rays on the formation of sugars (aldoses). To verify the effects of ammonia on the formation of sugars, we conducted gamma-rays irradiation experiments with various fractions of ammonia in the starting solutions.
Experimental
To simulate aqueous alteration inside the meteoric parent bodies, the following solutions (200 μL) were prepared whose compositions were: (1) HCHO : CH3OH : NH3 : H2O = 5:0.83:x:100 (the mixture was called FAW), (2) HCHO : CH3OH : NH3 : glycolaldehyde (GA) : H2O = 5:0.83:x:1:100 (the mixture was called FAGW) were prepared. Here, x was varied as (1) x=0, 0.5, 1, 2, 3, 4, 5, (2) x=0, 1, 5. CH3OH was added as a stabilizer for formaldehyde reagent. These samples were heated (50 ℃, 72 h) or gamma-rays irradiated (60Co source, 1.5 kGy/h, 60 h) and analyzed by gas chromatography mass spectrometry (GC/MS) after aldononitrile acetate ester derivatization [6]. We analyzed 3-6 carbons aldoses.
Results and Discussions
[Comparison of heating and gamma-rays irradiation]
In FAW, amounts and varieties of aldoses produced by gamma-rays irradiation tended to be greater than those of heated samples. On the other hand, FAGW produced the same amounts and varieties of aldoses by both energy sources. These results suggest that in the γ-rays irradiated FAW samples, GA was produced by a radical reaction [8], which facilitated the formose-type reactions and increased the production of sugars.
[Effects of starting materials]
The large amounts of aldoses obtained with FAGW suggests that the presence of GA is important for the formation of sugars. As for the effects of ammonia, the largest amounts of aldoses were produced when NH3/HCHO = 0.1-0.2, and the amounts of aldoses decreased as the amount of ammonia increased. These results suggest that ammonia has two functions: to catalyze reactions and to inhibit the formation of aldoses or to convert the generated sugars to other substances.
Summary
The presence of GA is important for the formation of sugars. The formation of GA from HCHO by gamma-rays suggests that gamma-rays also promoted sugar formation in the meteorite parent bodies. Ammonia was shown to both promote and inhibit the formation of sugars in formose-type reactions.
References
[1] Y. Furukawa et al., PNAS, 2019, 116, 24440-24445.
[2] G. Cooper et al., Nature, 2001, 414, 879-883.
[3] T. Koga et al., Scientific reports, 2017, 7, 636.
[4] Y. Kebukawa et al., Science Advances, 2017, 3, e1602093.
[5] AL.Weber, Orig. Life Evol. Biosph., 2001, 31, 71-86.
[6] K. Kobayashi et al., Bunseki Kagaku, 1989, 38, 608-612.
[7] Y. Kebukawa et al., ACS Cent. Sci., 2022, 8, 1664-1671.
[8] A. López-Islas et al., Int. J. Astrobiol., 2018, 18, 420-425.