title: Geochemical evolution of amino acids in dentine of Pleistocene bears.
abstract: A linear correlation was established between aspartic acid racemization ratio from cave bear dentine collagen and absolute dating. The high correlation coefficient obtained allowed age calculation through amino acid racemization. Aspartic acid and glutamic acid racemization kinetics have also been explored in dentine from a North American black bear (Ursus americanus Pallas). Three sample sets were prepared for kinetic heating experiments in nitrogen atmosphere: one water soaked, one with a water-saturated nitrogen atmosphere, and one without any moisture. It was possible to show that the presence of water is a factor controlling amino acid racemization rate. The aspartic acid in a heating experiment at 105 degrees C shows an "apparent kinetics reversal" which can be explained by a progressive hydrolysis of amino acid chains (proteins and polypeptides). Because of the low potential of collagen preservation over long periods of time, the apparent kinetics reversal phenomenon will not affect the dating of old material where no traces of collagen remain. An apparent kinetics reversal was not observed in glutamic acid, which racemizates more slowly.
authors.affiliation: Biomolecular Stratigraphy Laboratory, Madrid School of Mines, Rios Rosas 21, 28003 Madrid, Spain. museo@minas.upm.es
authors.forename: T
authors.initials: T
authors.lastname: De Torres
authors.forename: J E
authors.initials: JE
authors.lastname: Ortiz
authors.forename: M J
authors.initials: MJ
authors.lastname: García
authors.forename: J F
authors.initials: JF
authors.lastname: Llamas
authors.forename: L
authors.initials: L
authors.lastname: Canoira
authors.forename: M A
authors.initials: MA
authors.lastname: De La Morena
authors.forename: R
authors.initials: R
authors.lastname: Juliá
mesh_terms: D000366:Age Determination by Teeth / Q000379:methods; D000465:Algorithms; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry* / Q000378:metabolism; D003804:Dentin / Q000737:chemistry* / Q000378:metabolism; D019143:Evolution, Molecular; D005580:Fossils; D018698:Glutamic Acid / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D008956:Models, Chemical; D013237:Stereoisomerism; D001503:Ursidae
chemical_list: D001224:Aspartic Acid; D018698:Glutamic Acid