Aspartic Acid Racemisation
Definition
The slow spontaneous conversion of L-aspartic acid to D-aspartic acid in the non-remodelling enamel protein. Because the rate constant is known and is minimally affected by body temperature, the D/L ratio serves as a molecular clock from the moment enamel formed.
- Reaction
- L-aspartic acid converts to D-aspartic acid
- Tissue
- Non-remodelling enamel protein
- Basis of method
- Known, temperature-stable rate constant
- Use
- Molecular clock from enamel formation
Common questions
Why is enamel protein specifically used for this method rather than bone protein?+
Enamel does not remodel after formation, so its protein reflects a single fixed starting point, whereas bone collagen turns over throughout life, which would reset or blur the racemisation clock and make bone unsuitable for the same calculation.
What limits the accuracy of an age estimate from aspartic acid racemisation?+
The main limits are the precision of the analytical measurement of the D/L ratio and individual variation in the underlying rate constant, so results are typically reported with a confidence interval rather than as an exact age.
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