Collaborative Research: A Molecular Isotope Perspective on the Processes of Organic Matter Preservation in Fossils

合作研究：从分子同位素角度研究化石中有机物的保存过程

• 批准号: 9417836
• 负责人: Stephen Macko
• 金额: $ 14.02万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-02-01 至 1998-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9417836&HistoricalAwards=false
• 关键词: Collaborative; Research; Molecular; Isotope; Perspective

9417836 Macko Interpretations of the stable isotope record of residual organic matter in fossils requires a fundamental appreciation of the formation and transformation of the elemental pools of carbon and nitrogen during biosynthesis, diagenesis and preservation. A series of experiments are proposed to elucidate the effects of biosynthesis and diagenesis on the molecular and stable isotope composition of organic matter in biogenic minerals and sediments. Growth studies involving two species of planktonic foraminifera (Orbulina universa and Globigerina bulloides) will be conducted in collaboration with Dr. Howard Spero to compare the stable carbon and nitrogen isotope compositions of amino acid constituents of the shell protein to those of the diet. In addition to potentially identifying essential amino acids, the magnitude of isotope fractionations associated with trophic interactions will be assessed. A realistic assessment of biogenic signals from fossils requires an appraisal of the limits of isotope fractionation that can occur during diagenesis and the development of unambiguous criteria for evaluating the possible exchange of components with the preserving matrix. Simulation experiments are planned to evaluate the effects of diagenesis on the stable isotope composition of organic matter in fossils and sediments. Specifically, attempts will be made to assess the magnitudes of stable carbon and nitrogen isotope fractionations resulting from hydrolysis and humification. With respect to preservation, a major concern continues to be the ability to distinguish indigenous organic compounds from exogenous overprints. The further development of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) for stable nitrogen isotope analysis of amino acid enantiomers in fossils will provide an independent method for verifying the stable carbon isotope analysis of amino acid enantiomers, the development of GC/C/IRMS for stable nitrogen isotope analysis is dependent upon e stablishing isotopically reproducible combustion techniques capable of oxidation and reduction of halogenated derivatives of amino acids. An important test of this method involves molecular stable carbon and nitrogen isotope analysis of D- and L- enantiomers of individual amino acids in Cretaceous age samples, which will include dinosaur eggs and associated embryonic skeletal components. These rare samples are being provided from sites in North America and China by Dr. Dale Russell and Dr. Jack Horner. If the isotopic signals verify indigeneity, it may be possible to use molecular stable isotopes to establish the identities and trophic levels of the adults that produced the eggs. This study will also provide, to the best of our knowledge, the first direct comparison of the distribution and stable isotope composition of amino acid constituents of shell and bone from the same fossil organisms. An additional sample set of Cretaceous age dinosaurs from the western Sahara is also being provided by Dale Russell for a detailed investigation of organic matter preservation and paleoecology.

9417836 Macko 对化石中残留有机物的稳定同位素记录的解释需要对生物合成、成岩和保存过程中碳和氮元素库的形成和转化有基本的了解。 提出了一系列实验来阐明生物合成和成岩作用对生物矿物和沉积物中有机质的分子和稳定同位素组成的影响。 将与 Howard Spero 博士合作进行涉及两种浮游有孔虫（Orbulina universa 和 Globigerina bulloides）的生长研究，以比较壳蛋白氨基酸成分与饮食中氨基酸成分的稳定碳和氮同位素组成。 除了潜在地识别必需氨基酸之外，还将评估与营养相互作用相关的同位素分级的程度。 对化石生物信号的现实评估需要评估成岩过程中可能发生的同位素分馏的极限，并制定明确的标准来评估成分与保存基质的可能交换。 计划进行模拟实验来评估成岩作用对化石和沉积物中有机质稳定同位素组成的影响。 具体来说，将尝试评估水解和腐殖化产生的稳定碳和氮同位素分馏的程度。 在保存方面，一个主要问题仍然是区分本地有机化合物与外来套印的能力。 进一步发展化石中氨基酸对映体稳定氮同位素分析的气相色谱/燃烧/同位素比质谱（GC/C/IRMS）将为验证氨基酸对映体稳定碳同位素分析提供独立的方法，该发展GC/C/IRMS 用于稳定氮同位素分析的能力取决于建立能够氧化和还原氨基酸卤化衍生物的同位素可重复燃烧技术。 该方法的一项重要测试涉及对白垩纪样品中单个氨基酸的 D- 和 L- 对映体进行分子稳定碳和氮同位素分析，其中包括恐龙蛋和相关的胚胎骨骼成分。 这些稀有样本由戴尔·拉塞尔博士和杰克·霍纳博士从北美和中国的地点提供。 如果同位素信号验证了原生性，就有可能使用分子稳定同位素来确定产卵成虫的身份和营养水平。 据我们所知，这项研究还将首次对同一化石生物的壳和骨的氨基酸成分的分布和稳定同位素组成进行直接比较。 戴尔·拉塞尔还提供了一组来自西撒哈拉白垩纪恐龙的额外样本，用于有机物保存和古生态学的详细调查。