Temperature sensitivity of aspartic and glutamic acid racernization in the foraminifera Pulleniatina
Temperature sensitivity of aspartic and glutamic acid racernization in the foraminifera Pulleniatina
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DOI：
10.1016/j.quageo.2006.06.008
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发表时间：
2006-08-01
影响因子：
2.7
通讯作者：
Kaufman, Darrell S.
中科院分区：
文献类型：
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作者：
Kaufman, Darrell S.
在有孔虫属（Pulleniatina）的测试中，对天冬氨酸（Asp）和谷氨酸（Glu）的氨基酸外消旋化的温度敏感性进行了量化。来自盒芯样品顶部 1 厘米的 800 多个测试在 90 至 140 摄氏度的四个温度下加热长达 499 天，并单独进行分析以评估氨基酸外消旋化率。有孔虫在海水溶液中加热，与在无缓冲水中加热相比，海水溶液被认为是一种优质的孔隙流体。开发了一个三步筛选程序来系统地识别和排除异常值。评估了三个经验模型对给定温度下 D/L 随时间增加的模式以及深海条件下长期外消旋模式的拟合优度。简单的幂律函数（t 与 D/L-n 成比例）为等温条件下 Asp 和 Glu D/L 的进展提供了最佳拟合，Asp 的系数（n 值）优化为 3.0，Glu 的系数（n 值）优化为 2.4。将实验室加热实验的数据与 C-14 全新世 Pulleniatina 的数据相结合，将外消旋动力学的评估扩展到环境温度下的长期速率，以计算 Asp 和 Glu 外消旋的阿伦尼乌斯参数。与其他碳酸盐化石相比，Pulleniatina 外消旋化相对较慢，Asp 和 Glu 的 Ea 值分别为 31.5 +/- 0.2 和 31.2 +/- 0.3 kcal mol(-1)（131.0 +/- 0.8 和 131.9 +/- 1.3 kJ mol(-1)）。与年龄和古温度计算相关的误差是使用蒙特卡罗程序得出的，该程序传播了所有输入变量的综合效应。假设 +0.5 摄氏度的温度不确定性导致 Asp 的总体年龄误差约为 +/- 15%，Glu 的总体年龄误差约为 +/- 20%；有效成岩温度的实际不确定性约为 +/- 1 摄氏度。 (c) 2006 Elsevier Ltd. 保留所有权利。
The temperature sensitivity of amino acid racemization was quantified for aspartic acid (Asp) and glutamic acid (Glu) in tests of the foraminifera genus, Pulleniatina. More than 800 tests from the top I cm of a box core sample were heated for up to 499 days at four temperatures ranging from 90 to 140 degrees C, and were analyzed individually to evaluate the rate of amino acid racemization. The foraminifera were heated in a seawater solution, which was determined to be a superior pore fluid compared to heating in unbuffered water. A three-step screening procedure was developed to systematically identify and exclude outliers. Three empirical models were evaluated for their goodness of fit to the pattern of increasing D/L with time for a given temperature, and to the pattern of long-term racemization under deep-sea conditions. A simple power-law function (t proportional to D/L-n) provides the best fit to the progression of Asp and Glu D/L under isothermal conditions, with coefficients (n values) optimized at 3.0 for Asp and 2.4 for Glu. The data from laboratory-heating experiments were combined with data from C-14-dated Holocene Pulleniatina, which extended the evaluation of racemization kinetics to long-term rates at ambient temperatures, to calculate the Arrhenius parameters for racemization of Asp and Glu. Pulleniatina racemizes relatively slowly compared with other carbonate fossils, with Ea values of 31.5 +/- 0.2 and 31.2 +/- 0.3 kcal mol(-1) (131.0 +/- 0.8 and 131.9 +/- 1.3 kJ mol(-1)) for Asp and Glu, respectively. Errors associated with the age and paleotemperature calculations were derived using a Monte Carlo procedure that propagated the integrated effect of all input variables. Assuming a temperature uncertainty of +0.5 degrees C results in an overall age error of about +/- 15% for Asp and 20% for Glu; realistic uncertainties in effective diagenetic temperature are about +/- 1 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.