Age-dependent changes in the racemisation ratio of aspartic acid in human alveolar bone.

We investigated the racemisation ratio of aspartic acid (Asp) in alveolar bone. In addition, we designed and created a new column to detect Asp in a short period of time, which allowed us to detect d-Asp and l-Asp separately from each other within 5min. Comparing identical ages, the racemisation ratio of alveolar bone was generally lower than that of other bones reported so far. This result suggests that alveolar bone is metabolically more active than other bones, as expected. The rate constant for the racemisation reaction (k(y)) of alveolar bone was calculated to be 0.000338 in males and 0.000084 in females. The rate constants in males and females were each similar to the respective ratios of the femur. This result suggests that the age-dependent reduction in metabolic turnover in alveolar bone proceeds similarly to that in the femur, although those changes proceed more slowly in females than in males. The correlation coefficient between the racemisation ratio of alveolar bone and chronological age was 0.660. It was high in males (r=0.912) and low in females (r=0.527), and this gender difference was statistically significant (P: 0.01-0.001), as in the femur.

Novel chiral selectors anchored on polydimethylsiloxane as stationary phases for separation of derivatized amino acid enantiomers by capillary gas chromatography.

Six chiral selectors of S-(-)-t-Leu-cyclopropylamide, S-(-)-t-Leu-cyclopentylamide, S-(-)-t-Leu-cyclohexylamide, S-(-)-t-Leu-cycloheptylamide, S-(-)-t-Leu-cyclooctylamide, S-(-)-t-Leu-cyclododecylamide have been prepared and anchored individually through amide bonding to a polydimethylsiloxane functionalized with 2,2,2-trifluoroethyl ester groups by way of nucleophilic displacement reaction. The resulting chiral polysiloxanes have been provided as stationary phases for the separation of amino acid enantiomers by capillary GC. Amino acids were derivatized into N(O)-trifluoroacetyl isopropyl esters. Especially, polydimethylsiloxane anchored with S-(-)-t-Leu-cyclooctylamide was found to be efficient for the separation of aspartic acid (Asp) enantiomers. The method was applied to the estimation of ages from the extent of Asp racemization in human dentines.

An application of D- and L-aspartic acid mixtures as standard specimens for the chronological age estimation.

Instead of using the control teeth, we tried to prepare standard specimens to derive the equations for calculation of the age (analytical curves) with respect to each kind of tooth of various ages. To prepare standard specimens, we determined the racemization ratio of the teeth of known age that had actually been used for the appraisal of chronological age (total control teeth). Then we mixed commercially available L-Asp and D-Asp in the same D/L ratio as the measured one in the total control teeth. As a result, we were able to obtain the racemization rate equations from the age-specific standard specimens of central and lateral incisors. These equations were closely similar to those derived from actual teeth of known age. Since the racemization rate equations obtained from the standard specimens were satisfactorily reproducible, we assumed that these equations could be used in place of those obtained from the control teeth. Actually, in the age estimation of unidentified corpses from teeth, the use of standard specimens enabled us to estimate the age almost as precisely as estimated using the control teeth. Thus, the present study has demonstrated that in the estimation of chronological age the control teeth can be substituted by the standard specimens. This shows the possibility of using the standard specimens also in other laboratories where the racemization ratio can be measured with sufficient reproducibility.