17:15 〜 18:45
[MIS07-P02] Stability and Production of Amino Acids and Their Precursors of Interstellar Origin in the Interiors of Small Bodies in the Early Solar System
キーワード：アミノ酸前駆体、ガンマ線、星間塵、小天体
Ice mantles of interstellar dust particles in molecular clouds are one of the most suitable sites for prebiotic molecular formation. Organic compounds including amino acids are thought to have been produced by galactic cosmic ray irradiation in the ice mantle around the nucleus of dust particles in molecular clouds [1].
Previous studies have shown that macromolecular amino acid precursors (CAW) are produced from carbon monoxide, ammonia, and water abiotically in experiments simulating molecular clouds [2]. It was possible that the amino acid precursors produced in interstellar molecular clouds were incorporated into the primitive small bodies during the solar system formation, and were affected by gamma-rays and heat from the radioactive decay of 26Al.
Considering these factors, experiments were conducted to investigate the stability of amino acids and macromolecular amino acid precursors against gamma-rays in the interior of small bodies. Glycine or CAW was dissolved in ammonia aqueous solution or in an aqueous solution of formaldehyde and ammonia. These solutions were irradiated with gamma-rays from 60Co source. The results showed that macromolecular amino acid precursors from molecular clouds (CAW) were more stable than free amino acids against gamma-ray irradiations in an environment that simulates the interior of small bodies. Moreover, we confirmed that amino acids can be newly synthesized by gamma-ray irradiation.
In conclusion, biologically relevant organic compounds formed in interstellar molecular clouds might be delivered to the early Earth as the form of macromolecular amino acid precursors. Furthermore, alterations in small bodies could further produce novel chemical species.
Some amino acids found in carbonaceous chondrites showed enantiomeric excesses. Such excesses might have been generated and/or enlarged during hydrolytic processes in asteroids. Such possibilities will be examined by adding seeds of enantiomeric excesses to a mixture of formaldehyde, ammonia, and water [3]. For future work, we are planning to use amino acids such as DL alanine and examine the influences of the small body environments for their stereochemistry.
References
[1] Kasamatsu, T. et al., Formation of organic compounds in simulated interstellar media with high energy particles., Bull. Chem. Soc. Jpn., 70, 1021-1026 (1997).
[2] Takano, Y., et al., Pyrolysis of Complex Organics Following High-Energy Proton Irradiation of Simple Inorganic Gas Mixture. Appl. Phys. Lett., 85, 1633-1635 (2004).
[3] Cronin, J. R. and Pizzarello, S., Enantiomeric excesses in meteoritic amino acids, Science, 275, 951-955 (1997).
Previous studies have shown that macromolecular amino acid precursors (CAW) are produced from carbon monoxide, ammonia, and water abiotically in experiments simulating molecular clouds [2]. It was possible that the amino acid precursors produced in interstellar molecular clouds were incorporated into the primitive small bodies during the solar system formation, and were affected by gamma-rays and heat from the radioactive decay of 26Al.
Considering these factors, experiments were conducted to investigate the stability of amino acids and macromolecular amino acid precursors against gamma-rays in the interior of small bodies. Glycine or CAW was dissolved in ammonia aqueous solution or in an aqueous solution of formaldehyde and ammonia. These solutions were irradiated with gamma-rays from 60Co source. The results showed that macromolecular amino acid precursors from molecular clouds (CAW) were more stable than free amino acids against gamma-ray irradiations in an environment that simulates the interior of small bodies. Moreover, we confirmed that amino acids can be newly synthesized by gamma-ray irradiation.
In conclusion, biologically relevant organic compounds formed in interstellar molecular clouds might be delivered to the early Earth as the form of macromolecular amino acid precursors. Furthermore, alterations in small bodies could further produce novel chemical species.
Some amino acids found in carbonaceous chondrites showed enantiomeric excesses. Such excesses might have been generated and/or enlarged during hydrolytic processes in asteroids. Such possibilities will be examined by adding seeds of enantiomeric excesses to a mixture of formaldehyde, ammonia, and water [3]. For future work, we are planning to use amino acids such as DL alanine and examine the influences of the small body environments for their stereochemistry.
References
[1] Kasamatsu, T. et al., Formation of organic compounds in simulated interstellar media with high energy particles., Bull. Chem. Soc. Jpn., 70, 1021-1026 (1997).
[2] Takano, Y., et al., Pyrolysis of Complex Organics Following High-Energy Proton Irradiation of Simple Inorganic Gas Mixture. Appl. Phys. Lett., 85, 1633-1635 (2004).
[3] Cronin, J. R. and Pizzarello, S., Enantiomeric excesses in meteoritic amino acids, Science, 275, 951-955 (1997).