On the reported optical activity of amino acids in the Murchison meteorite
Abstract
In analyses of extracts from the Murchison meteorite (a carbonaceous chondrite), Engel and Nagy1 reported an excess of L-enantiomers for several protein amino acids but found that the non-protein amino acids were racemic. They suggested that the excess of L-isomers might have resulted from an asymmetric synthesis or decomposition. Their results disagree with those obtained previously2-4 and they claim this is due to improved methodology. In fact, their extraction method and analytical procedure (gas chromatography-mass spectrometry, GC-MS) was similar to those used in the original report2 of amino acids in the Murchison meteorite except that they used specific ion monitoring in the GC-MS measurements. We found the results of Engel and Nagy odd in that likely contaminants (the protein amino acids ala, leu, glu, asp and pro) were nonracemic while unlikely contaminants (isovaline and α-amino-n-butyric acid) were racemic. For example, Engel and Nagy report that the leucine is ~90% L-enantiomer in the water-extracted sample whereas isovaline (α-methyl-α-aminobutyric acid) is racemic. It would be most unusual for an abiotic stereoselective decomposition or synthesis of amino acids to occur with protein amino acids but not with non-protein amino acids. We now show here that the explanation of terrestrial contamination is consistent with their results and is much more probable.
- Publication:
-
Nature
- Pub Date:
- February 1983
- DOI:
- 10.1038/301494a0
- Bibcode:
- 1983Natur.301..494B
- Keywords:
-
- Amino Acids;
- Meteoritic Composition;
- Abundance;
- Contamination;
- Optical Activity;
- Lunar and Planetary Exploration; Meteorites;
- METEORITES;
- OPTICAL PROPERTIES;
- AMINO ACIDS;
- MURCHESON METEORITE;
- DATA;
- CONTAMINATION;
- ANALYSIS;
- ORGANIC COMPOUNDS;
- ABUNDANCE;
- PROCEDURE;
- TECHNIQUES;
- MODELS;
- GAS CHROMATOGRAPHY;
- MASS SPECTROMETRY