アミノ酸のラセミ化による年代測定  [in Japanese] Age determination by the racemization of amino acids  [in Japanese]

This paper is a review of studies on amino acid racemization used as a molecular clock, including its basic reaction mechanisms, factors controlling the reaction rates, analytical methods for D/L ratios and some comments on application to geochronology. There is a variety of amino acids whose racemization rate constants are different, so that age determination can be possible for geological samples over several thousand to several million years old. However, dating these samples by the racemization should be done with a great care on evaluation of thermal and environmental conditions during geological history. Another care should be taken for the dating, because even the same kind of amino acids has a different rate constant, depending on its chemical form, free or derived peptide or protein. It seems that amino acids in diagenetically survived proteins could give the best result for the dating. The degree of the racemization can also be used for stratigraphic correlation (aminostratigraphy).