Radiocarbon Dating of Bone Osteocalcin: Isolating and Characterizing a Non-Collagen Protein

Osteocalcin, a non-collagen bone-matrix protein, has been examined as a possible source of autochthonous14C data in fossil bones where collagen has been seriously degraded. Extraction procedures for osteocalcin yield a well-characterized product that can be clearly distinguished from collagen. The Gla content indicates that osteocalcin is present in the fossil bones at levels similar to the range present in modern bone. However, it appears to be extracted primarily as proteolytic polypeptide fragments rather than as an intact protein. Concordant14C determinations are obtained on osteocalcin and gelatin extracts from the same bone when the collagen is relatively well preserved. However, increasing discordances in the14C values of the osteocalcin and gelatin fractions are associated with reduced concentrations of the gelatin extract in the bone.