Racemization of Meteoritic Amino Acids

Radiolysis and radioracemization of 20 amino acids from the beginning of the Solar System

“…The almost unique source of degradation and processing of the organic material occurring in 4.6 9 10 9 years (the Solar System age) at a depth [20 m in comets or asteroid derives almost exclusively by the radionuclide decay (Draganic et al 1993). It should be considered that the a-amino acid racemisation is negligible in a dry environment and at temperature \270 K while the racemisation in aqueous solution is relatively rapid (Coen and Chyba 2000). Thus, in our model, it was assumed that the amino acids were embedded in comet, asteroid or in other bodies of the Solar System in a completely dry state for 4.6 9 10 9 years without episodes of water alteration.…”

Gas chromatographic enantioseparation of derivatized α-amino acids on chiral stationary phases—Past and present

“…However, only in 1975 the first supporting evidence was provided by demonstrating the age dependent accumulation of d-aspartic acid in enamel [160]. The racemization of ␣-amino acids (and the epimerization of peptides) requires modern methods of enantiomeric analysis and it resulted in a widely discussed topic in the literature [161][162][163][164][165][166][167]. The time-dependent racemization of ␣-amino acids is of great interest for (i) dating of fossils and archeological artifacts by determining the d/l ratio of ␣-amino acids (amino stratigraphy), especially those present in metabolically inert matrices such as tooth enamel or in collagen, e.g., aspartic acid (cf.…”

Photochirogenesis: Photochemical Models on the Origin of Biomolecular Homochirality

“…Considering that the α-methyl amino acids in the Murchison fragment have been subject to racemization [84] and heating in the parent asteroid, the enantiomeric excess reported by the above mentioned studies may represent the lower limits of L-amino acid enrichment.…”