Estimation of age at death based on aspartic acid racemization in noncollagenous bone proteins.

Age at death determination based on the extent of aspartic acid racemization in dentin has been reported to be highly accurate and reproducible. To test the applicability of this method to human bone, aspartic acid racemization in noncollagenous proteins of bone was investigated. A close relationship was found between age at death and the extent of aspartic acid racemization in osteocalcin, the most abundant noncollagenous protein of the organic bone matrix. Our findings indicate that osteocalcin is a permanent, 'aging' constituent of the organic bone matrix whose D-aspartic acid content increases with age because of in vivo racemization. Thus, the extent of aspartic acid racemization in bone osteocalcin is a measure of the age of the peptide and hence of the entire organism. The relationship between age at death and the extent of aspartic acid racemization in purified bone osteocalcin appears to be close enough to serve as a basis for determination of age at death in forensic medicine.