COMPARISON OF BONE-COLLAGEN AND OSTEOCALCIN FOR DETERMINATION OF RADIOCARBON AGES AND PALEODIETARY RECONSTRUCTION

Osteocalcin, a gamma-carboxyglutamic acid containing bone protein, is tightly bound to the hydroxyapatite matrix of bone, and as a consequence it is relatively more stable than the dominant protein, collagen. Its distribution in nature is limited to vertebrates. Osteocalcin and collagen have been isolated from modern and fossil bone samples of different organisms in different depositional environments for analysis of their delta-C-13, delta-N-15 and C-14 content. Whereas collagen is susceptible to aqueous weathering, hydrolysis, solubilization and removal, as well as contamination by soil amino acids or peptides, osteocalcin is more strongly bonded to the apatite matrix of the bone and hence less prone to loss or replacement by contaminants. We present evidence suggesting that osteocalcin may be a more suitable protein fraction for obtaining accurate C-14 age estimates and/or delta-C-13 and delta-N-15 for paleodietary reconstruction from bone samples.