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

小行星9504618 化石中残余有机质稳定同位素记录的解释需要对生物合成、成岩作用和保存过程中碳和氮元素库的形成和转化有基本的认识。 通过一系列实验，阐明了生物合成和成岩作用对生物矿物和沉积物中有机质分子组成和稳定同位素组成的影响。 将与霍华德·斯佩罗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，以比较壳蛋白质与饮食中氨基酸组分的稳定碳和氮同位素组成。 除了可能识别必需氨基酸外，还将评估与营养相互作用相关的同位素分馏的大小。 一个现实的生物信号从化石的评估，需要评估的限制同位素分馏，可能发生在成岩作用和明确的标准，以评估可能的交换与保存矩阵的组件的发展。 通过模拟实验研究了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。 具体而言，将试图评估水解和腐殖化产生的稳定碳和氮同位素分馏的大小。 在保存方面，一个主要关切仍然是能否区分本地有机化合物和外来叠印。 气相色谱/燃烧/同位素比质谱联用技术的进一步发展（GC/C/IRMS）用于化石中氨基酸对映体的稳定氮同位素分析，将为验证氨基酸对映体的稳定碳同位素分析提供一种独立的方法，GC/C/用于稳定氮同位素分析的IRMS依赖于建立能够氧化和还原氮的同位素可重复的燃烧技术。氨基酸的卤代衍生物。 该方法的一个重要测试涉及白垩纪样品中单个氨基酸的D-和L-对映体的分子稳定碳和氮同位素分析，这些样品将包括恐龙蛋和相关的胚胎骨骼成分。 这些罕见的样本由Dale Russell博士和Jack Horner博士从北美和中国的研究中心提供。 如果同位素信号证实是独立的，那么就有可能使用分子稳定同位素来确定产卵的成虫的身份和营养水平。 据我们所知，这项研究还将首次直接比较来自同一化石生物的壳和骨的氨基酸组分的分布和稳定同位素组成。 戴尔·拉塞尔还提供了一套来自西撒哈拉的白垩纪恐龙样本，用于详细调查有机物保存和古生态学。

9504618 Engel 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.