The Search for Novel High Molecular Weight Biomarkers (>C40)in Geological Samples of All Ages

生物标志物是指地质样品中的化合物，其基本碳骨架类似于其前体的化合物，这些前体存在于藻类、细菌和高等植物等来源物质中。到目前为止，已发现的生物标志物大多在C10-C40范围内。层析和质谱学的局限性阻碍了对C40以上区域生物标记物的成功调查和鉴定。建议利用高温毛细管柱和串联质谱仪的发展，进入C40-C100范围内生物标志物地球化学的前沿领域。从各种特征良好的石油和源岩中提取的萃取物将通过串联质谱仪与气相色谱或直接插入探头相结合进行研究。选定的样品将是那些其低分子量生物标记物已经被广泛表征的样品。最初，分析这种新型高分子量组分所需的最佳分析条件将通过使用已知含有长链正构烷烃的自然产生的蜡来确定。在一种平行的方法中，将尝试通过荷酸和合适的烷烃或类异戊二烯的缩合来合成高相对分子质量的荷帕烷标准。利用GC-MS/MS和直接插入探针MS/MS对产物进行了表征，并建议将串联质谱仪与微热裂解技术相结合，用于研究干酪根、原干酪根和其他难溶有机物质热解过程中产生的高分子量碎片。这类化合物的鉴定将扩大生物标志物在地球化学许多方面的应用。这将有助于更好地了解古气候和古环境、生物化学演化以及影响石油组成和演化的过程。随着仪器技术的进步，预计高分子量生物标志物的研究将会有越来越多的进展。这项提议是对这些化合物的第一次正式和系统的搜索。

Biomarkers are compounds in geological samples whose basic carbon skeleton resembles that of their precursors which occur in source materials such as algae, bacteria and higher plants. For the most part the biomarkers discovered to date have been in the C10-C40 range. Limitations in both chromatography and mass spectrometry have prevented the successful investigation and identification of biomarkers in the region above C40. It is proposed to take advantage of developments of high temperature capillary columns and tandem mass spectrometers to enter into the frontier area of biomarker geochemistry in the range of C40-C100. Extracts from a variety of well characterized oils and source rocks will be investigated by tandem mass spectrometry in combination with gas chromatography or the direct insertion probe. The samples selected will be those whose lower molecular weight biomarkers have already been extensively characterized. Initially optimum analytical conditions required for the analyses of such novel high molecular weight components will be determined by the use of naturally occurring waxes known to contain long chain n-alkanes. In a parallel approach, attempts will be made to synthesize high molecular weight hopane standards by condensation of hopanoic acids and suitable alkanes or isoprenoids. The resultant products will be characterized by GC- MS/MS and direct insertion probe MS/MS. In addition it is proposed to use tandem mass spectrometry in combination with micropyrolysis techniques to investigate the high molecular weight fragments produced by pyrolytic degradation of kerogens, protokerogens and other insoluble organic materials. The identification of such compounds will expand the utility of biomarkers in many aspects of geochemistry. It should result in a better understanding of paleoclimate and paleoenvironment, biochemical evolution and processes affecting petroleum composition and evolution. With the advances in instrumental technology it is anticipated that there will be an increasing move towards the study of high molecular weight biomarkers. This proposal presents the first formal and systematic search for these compounds.//