Amino Acid Racemization as a Dating Method

Amino Acid Racemization as a Dating Method

David A. Plaisted

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An article in the Dec 13, 1996 issue of Science, page 1842, discusses dating based on the amino acid racemization technique. In proteins, amino acids only come in the L (left?) form, but with time some transform to the D (right) form. So, by examining how many have shifted, one can estimate the age of the sample. Gould and Goodfriend used this to date some snails. Now, my question is, what's the chance that an amino acid will shift to the D form in say, one year. This could easily be measured. I suppose it may depend on heat and pressure, but this dependence can also be measured. Then one could use this as an independent test on other dating schemes. I heard of a case where ancient fossils were dated this way and turned out to be tens of thousands of years old, rather than millions of years old. Of course, since this technique may be calibrated in terms of Carbon 14 dating, which itself may be open to question, even those dates may be wrong. Anyway, I'd be interested to know, if one extrapolates known (laboratory measured) rates of racemization back in time, what kind of a check does this give on Carbon 14 and other dating methods.

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