Optical Isomers, Chirality, and Racemization

The L-isomer of any compound can transform into the D-isomer, and vice versa. A mixture of equal amounts of the l- and D-isomers of a compound is said to be a racemic mixture, and the process whereby an isomer. 

There is, however, a drawback to this method of dating. The half-life (see Textbox 14) of the racemization process is greatly affected by temperature it is shorter at higher temperatures and slows down as the temperature decreases. An xmcertainty of 2°C in the temperature history of dead remains can lead to an error of about 50% in the age determined. For the racemization of amino acids to be applicable for dating, therefore, it is crucial that the temperature history of the environment where the amino acids (that is, skin or bone) have been deposited should be well known. 

Two different types of DNA occur in distinct locations in the living cell nuclear DNA in the cell s nucleus and mitochondrial DNA (mt-DNA) in the mitochondria (see Textbox 50). RNA occurs in several types messenger RNA, transfer RNA, ribosomal RNA, and others, all in the cytoplasm of the cells (see Table 85) (Bloomfield et al. 2000). 

Archaeological Chemistry, Second Edition By Zvi Goffer Copyright 2007 John Wiley Sons, Inc. 

DNA Deoxyribonucleic acid Carries genetic instructions for maldng living organisms 

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