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

从化石中分离出的有机物质为确定基于同位素和氨基酸数据的古生态和分类关系提供了潜在的基础。目前评估原生生物的标准主要集中在来自化石的大块有机组分上，包括氨基酸丰度和对映体的分析，以及化石材料与现代生物的13C和15N值的比较。这些标准包括两个假设：1)大块有机物质是均匀的；2)氨基酸和同位素组成的相对丰度与现代类似物相当。这些假设的困难在于，大块材料不是均匀的，而是由几种不同的蛋白质组成的，化石的有机基质可能会改变。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对数据的解释完全是有机基质蛋白质组成的函数。因此，需要更精确和新的方法来评估成岩作用的影响，并得出原生标准。为了更好地理解化石材料有机组分随时间的变化，必须包括：1)评估每个蛋白质组分随时间的相对贡献的变化；2)理解成岩作用期间单个蛋白质组分生化特征的变化；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）。我们期望通过对单个蛋白质的分子水平分析，为成岩作用提供独特的信息。

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.