Reference Work Entry

Encyclopedia of Genetics, Genomics, Proteomics and Informatics

pp 1620-1620



This is a Mixture of D and L optical stereoisomers (enantiomorphs) which subsequently becomes optically inactive. All naturally synthesized amino acids are in the L form but degradation generates the D enantiomorph. The degree of racemization of aspartic acid is faster than that of other amino acids. It has been recently used to determine the authenticity of ancient samples of DNA because the degradation of DNA and the racemization of amino acids, particularly Asp, indicate whether the spurious DNA is really ancient or just a contaminant in the archeological sample. In case the D/L Asp ratio exceeds 0.08 the ancient DNA cannot be retrieved. Degradation also depends on a number of factors, most notably the temperature to which the specimen had been historically exposed. The best preservation has been observed in insects enclosed in amber (although there is some controversy about these samples). In specimens where the D/L Asp ratio is about 0.05, up to 340 bp long DNA sequences can be detected using PCR technology. enantiomorph, radiocarbon dating, evolutionary clock

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