Racemization velocity of aspartic acid in dentine.

To investigate the racemization of dentinal amino acids furthermore, and thereby to estimate age more accurately, fundamental heating experiments dealing with aspartic acid in dentine were carried out. The racemization velocity was determined and compared not only for the total amino acids (TAA), but for insoluble collagen (IC) as well as soluble peptide (SP) fractions. In TAA and IC, with the passage of time, their racemization deviated from the mode of the primary reaction, whereas in the SP, an extremely stable increase in D/L ratio was maintained for a longer time, fulfilling the mode of the primary reaction. When samples are left drying, the racemization velocity was greatest in the IC but considerably less in the SP, indicating results opposite to those found in the living state.