Abstract
Amino acids identified in the Murchison chondritic meteorite by molecular and isotopic analysis are thought to have been delivered to the early Earth by asteroids, comets, and interplanetary dust particles where they may have triggered the appearance of life by assisting in the synthesis of proteins via prebiotic polycondensation reactions [Oró, J. (1961) Nature 190, 389-390; Chyba, C. F. & Sagan, C. (1992) Nature 355, 125-132]. We report the identification of diamino acids in the Murchison meteorite by new enantioselective GC-MS analyses. dl-2,3-diaminopropanoic acid, dl-2,4-diaminobutanoic acid, 4,4'-diaminoisopentanoic acid, 3,3'-diaminoisobutanoic acid, and 2,3-diaminobutanoic acid were detected in the parts per billion range after chemical transformation into N,N-diethoxycarbonyl ethyl ester derivatives. The chiral diamino acids show a racemic ratio. Laboratory data indicate that diamino acids support the formation of polypeptide structures under primitive Earth conditions [Brack, A. & Orgel, L. E. (1975) Nature 256, 383-387] and suggest polycondensation reactions of diamino acids into early peptide nucleic acid material as one feasible pathway for the prebiotic evolution of DNA and RNA genomes [Joyce, G. F. (2002) Nature 418, 214-221]. The results obtained in this study favor the assumption that not only amino acids (as the required monomers of proteins) form in interstellar/circumstellar environments, but also the family of diamino monocarboxylic acids, which might have been relevant in prebiotic chemistry.