No abstract

The Yamato-791198 and Murchison carbonaceous chondrites were analyzed for dipeptides and diketopiperazines as well as amino acids and hydantoins by gas chromatography combined with mass spectrometry. Glycylglycine (gly-gly) and cyclo(gly-gly) were detected at the concentrations of 11 and 18 pmol g-1, respectively, in Yamato-791198, and 4 and 23 pmol g-1, respectively, in Murchison. No other dipeptide and diketopiperazine were detected. Five hydantoins were detected at 8 to 65 pmol g-1 in Yamato-791198 and seven in Murchison at 6 to 104 pmol g-1. Total concentration of the glycine (gly) dimers is approximately four orders of magnitude less than the concentration of free gly in Yamato-791198, and three orders of magnitude less than that in Murchison. The absence of L- and LL-stereoisomers of dipeptides consisting of protein amino acids indicates that gly-gly and cyclo(gly-gly) detected are native to the chondries and not from terrestrial contaminants. A possibility was discussed that the gly dimers might have been formed by condensation of gly monomers but not formed through N-carboxyanhydrides of gly.

No abstract

No abstract

The Yamato-791198 carbonaceous chondrite yielded indigenous amino acids. These consitst of various structural and optical isomers, indicating abiotic in origin. The amount of these amino acids is the largest of carbonaceous chondrites studied so far. Terrestrial organic contamination was nil to this chondrite.