ISOTOPIC ANALYSES OF AMINO-ACIDS FROM THE MURCHISON METEORITE

Previous isotopic analyses of the total amino acids of the Murchison meteorite showed these compounds to be substantially enriched in H-2, C-13, and N-15 relative to terrestrial organic matter. These analyses have been repeated (H-2, C-13) with inclusion of an ultrafiltration step to exclude the possibility that a fine particulate contaminant carried the isotopic excesses observed in the previous work. In addition, the meteorite amino acids were chromatographically separated to rule out the possibility that the isotopic enrichment of the meteorite extract could reside in basic compounds other than amino acids. The results indicate that the Murchison amino acids are truly isotopically unusual, that the isotopic excesses reside in at least several different amino acids, and that the isotopic contents of some of these amino acids reach values of about +40 parts per thousand (delta-C-13) and +2500 parts per thousand (delta-D). If it is assumed that the high deuterium content of the meteorite alpha-amino acids is a result of the synthesis of their molecular precursors by low temperature ion-molecule reactions in an interstellar cloud, their formation by aqueous phase Strecker reactions in the parent body is consistent with their general characteristics and with known parent body processes.