A new method for enamel amino acid racemization dating: A closed system approach
A new method for enamel amino acid racemization dating: A closed system approach
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DOI：
10.1016/j.quageo.2018.11.005
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发表时间：
2019-03-01
影响因子：
2.7
通讯作者：
Penkman, Kirsty E. H.
中科院分区：
文献类型：
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作者：
Dickinson, Marc R.;Lister, Adrian M.;Penkman, Kirsty E. H.
分析：古代生物矿物中蛋白质和氨基酸的可预测分解使第四纪的年龄估计成为可能。我们假设，釉质是一个合适的内源性氨基酸的长期生存的生物矿物。用于地质年代学研究的多种氨基酸分析通常使用RP-HPLC方法实现。然而，低浓度的氨基酸加上高浓度的无机物质使得准确测定氨基浓度具有挑战性。我们已经开发了一种使用两相分离的多个釉质样品的常规制备方法。此外，我们已经表明，氨基酸，表现出有效的封闭系统的行为，可以从牙釉质通过暴露时间为72小时的漂白剂分离。研究晶体内蛋白质降解（IcPD）过程的高温实验似乎与化石样品的模式不匹配，这加强了对蛋白质降解潜在机制的全面理解的必要性。这种新的制备方法分离的晶体内的氨基酸适合于发展的哺乳动物地质年代学的基础上釉质蛋白质降解。釉质中的外消旋化速率较低（参见Bithynia opercula）的结果表明，在大于2.8Ma的时间尺度上，釉质AAR可以作为一种相对定年技术。搪瓷AAR有可能直接定年哺乳动物仍然过去的限制，目前所有其他直接定年方法，提供了一个宝贵的工具，地质年代学研究。
Analysis: of the predictable breakdown of proteins and amino acids in ancient biominerals enables age estimation over the Quaternary. We postulate that enamel is a suitable biomineral for the long-term survival of endogenous amino acids. Analysis of multiple amino acids for geochronological studies is typically achieved using a RP-HPLC method. However, the low concentrations of amino acids coupled with high concentrations of inorganic species make accurate determination of amino concentrations challenging. We have developed a method for the routine preparation of multiple enamel samples using biphasic separation. Furthermore, we have shown that amino acids that exhibit effectively closed system behaviour can be isolated from enamel through an exposure time of 72 h to bleach. Elevated temperature experiments investigating the processes of antra-crystalline protein degradation (IcPD) do not appear to match the patterns from fossil samples, reinforcing the need for a comprehensive understanding of the underlying mechanisms of protein degradation. This novel preparative method isolates intra-crystalline amino acids suitable for the development of mammalian geochronologies based on enamel protein degradation. The lower rates of racemization in enamel (cf. Bithynia opercula) suggest that the enamel AAR may be able to be used as a relative dating technique over time scales > 2.8 Ma. Enamel AAR has the potential to directly date mammalian remains past the limit of all other current direct dating methods, providing an invaluable tool for geochronological studies.