AMINO-ACID RACEMIZATION REACTIONS AND THEIR GEOCHEMICAL IMPLICATIONS
AMINO-ACID RACEMIZATION REACTIONS AND THEIR GEOCHEMICAL IMPLICATIONS
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DOI：
10.1007/bf00592179
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发表时间：
1975-01-01
影响因子：
--
通讯作者：
SCHROEDER, RA
中科院分区：
文献类型：
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作者：
BADA, JL;SCHROEDER, RA
存在于生物体中的氨基酸主要由L-对映体组成。在漫长的地质时期，氨基酸经历了缓慢的外消旋化，产生z~-对映体。化石材料中所含的氨基酸显示出随着年龄的增长而增加的外消旋化程度。本文讨论了氨基酸外消旋反应的动力学和机理，以及该反应在地质年代学和古温度测定中的应用。巴斯德在120多年前首先证明了从野豌豆植物中分离的氨基酸天冬酰胺是光学活性的。在生物圈中发现了一些D-氨基酸，但与大部分生物物质中含有的L-氨基酸相比，这些氨基酸的量很小[21]。近90年前，人们发现氨基酸在浓酸中加热时会发生外消旋化（将光学活性分子转化为光学惰性混合物的反应）[3，41和碱[5，6]。然而，直到最近才证明，当在高温下加热时，氨基酸在中性pH下也会发生外消旋化，并且速率仅略低于酸性或碱性溶液[7，8]。此外，已经发现氨基酸外消旋化反应不仅在水溶液中发生，而且在固体无机基质如骨和壳中发生。化石材料已被证明含有D-和L-氨基酸，并且D-与L-氨基酸的比例随着化石的年龄而增加
The amino acids present in living organisms consist mainly of the L-enantiomers. Over long periods of geological time, amino acids undergo a slow racemization, producing the z~-enantiomers. The amino acids contained in fossil materials show an increasing extent of racemization with age. The kinetics and mechanism of amino acid racemization and the applications of this reaction in geochronology and paleothermometry are discussed.Pasteur first demonstrated over 120 years ago that the amino acid asparagine, isolated from vetch plants, was optically active [tl-It is now a well-known fact that the amino acids commonly found in living organisms consist almost entirely of the L-enantiomers. Some D-amino acids are found in the biosphere, but the amount of these is small compared to the L-amino acids contained in the bulk of living matter [21. Nearly 90 years ago, it was shown that amino acids undergo racemization (the reaction in which an optically-active molecule is converted into an opticallyinactive mixture) when heated in concentrated acid [3, 41 and base [5, 6]. However, it was not until recently that it was demonstrated that amino acids also undergo racemization at neutral pH, when heated at elevated temperatures, and the rates are only slightly slower than in acidic or basic solution [7, 8]. Moreover, the amino acid racemization reaction has been found to take place not only in aqueous solutions, but also in solid inorganic matrixes such as bone and shell. Fossil materials have been shown to contain both D-and L-amino acids, and the proportion of D-to L-amino acids increases with the age of the fossil