SGER: COLLABORATIVE RESEARCH: Biogeochemistry of Individual Proteins of Ancient and Modern Gastropods: A Molecular Level Approach to the Study of Diagenesis

从化石中分离出的有机物质为根据同位素和氨基酸数据确定古生态和分类关系提供了潜在的底物。目前的评估标准侧重于从化石中提取的大量有机部分，包括氨基酸丰度和对映体的分析，以及化石材料的13C和15N值与现代生物体的比较。这些标准包含两个假设：1)大部分有机物质是均质的，2)氨基酸的相对丰度和同位素组成与现代类似物相当。这些假设的困难在于，大块物质不是均匀的，而是由几种不同的蛋白质组成，化石的有机基质可能会发生变化。如果从化石中获得的成岩产物是特定蛋白质组分的差异损失或保留的结果，那么地球化学特征和数据解释完全取决于有机基质的蛋白质组成。因此，需要更精确和新的方法来评估成岩作用的影响，并得出成岩作用的标准。要更好地了解化石物质有机组分随时间的变化，必须包括1)评估每一种蛋白质组分的相对贡献随时间的变化，2)了解成岩作用期间个别蛋白质组分的生化特征发生的变化，3)新的分子水平方法，例如评估单个氨基酸对映体的13C(见解释的理由)。我们预计，这项拟议的研究将通过对单个蛋白质的分子水平分析，提供关于成岩作用的独特信息。

Organic material isolated from fossils provides a potential substrate for determining paleoecological and taxonomic relationships based on isotopic and amino acid data. Present criteria for evaluating indigeneity has focused on a bulk organic fraction derived from fossils and includes analysis of amino acid abundances and enantiomers and comparison of the 13C and 15N values of the fossil material to those of the modern organism. These criteria incorporate two assumptions that 1) the bulk organic material is homogeneous and 2) the relative abundance of amino acids and the isotopic compositions are comparable to a modern analog. The difficulties with these assumptions are that the bulk material is not homogeneous but rather composed of several different proteins and the organic matrix of fossils may be altered. If the diagenetic product obtained from a fossil is a consequence of differential loss or retention of specific protein fractions then the geochemical characteristics and interpretation of the data are entirely a function of the protein composition of the organic matrix. Therefore, more precise and new methods are needed to assess the effects of diagenesis and derive criteria for indigeneity. A better understanding of changes in the organic fraction of fossil material over time must include 1) an evaluation of variation in the relative contributions of each of the protein fractions over time, 2) an understanding of the alterations that occur in the biochemical characteristics of individual protein fractions during diagenesis and 3) new molecular level approaches, such as evaluation of the 13C of individual amino acid enantiomers (see Justification of explanation). We anticipate that the proposed research will provide unique information on diagenesis through molecular level analyses on individual proteins.