C-14 DATING OF BONE USING GAMMA-CARBOXYGLUTAMIC ACID AND ALPHA-CARBOXYGLYCINE (AMINOMALONATE)

Radiocarbon determinations have been obtained on gamma-carboxyglutamic acid [Gla] and alpha-carboxyglycine (aminomalonate) [Am] as well as a cid- and base-hydrolyzed total amino acids isolated from a series of f ossil bones. As far as we are aware, Am has not been reported previous ly in fossil bone and neither Gla nor Am C-14 values have been measure d previously. Interest in Gla, an amino acid found in the non-collagen proteins osteocalcin and matrix Gla-protein (MGP), proceeds from the suggestion that it may be preferentially retained and more resistant t o diagenetic contamination affecting C-14 values in bones exhibiting l ow and trace amounts of collagen. Our data do not support these sugges tions. The suite of bones examined showed a general tendency for total amino acid and Gla concentrations to decrease in concert. Even for bo nes retaining significant amounts of collagen, Gla (and Am extracts) c an yield C-14 values discordant with their expected age and with C-14 values obtained on total amino-acid fractions isolated from the same b one sample.