The Role of Protein as a Contributor to Organic Nitrogen in the Ocean

大型难熔有机氮库在整个氮循环中的重要性已得到公认，但其化学组成和导致其抗性的机制(S)仍未得到回答。最近的工作证明了酰胺键对保存在沉积物和土壤中的有机氮的重要性。该项目的首席研究员和切萨皮克生物实验室的其他研究人员最近表明，蛋白质可以在早期成岩过程中保存下来，并从沉积物中提取出来。这一提议的首要前提是，那些被保存下来的蛋白质可能会保留其原始生物合成的信号，只需对其结构进行微小的修改。如果这是真的，那么单个蛋白质和混合物的结构鉴定可以用来详细说明这些蛋白质的来源和可能的加工过程，从而使它们最终能够并入沉积物中。因此，该项目有两个目标：采用目前的质谱学方法分析蛋白质的一级结构，以确定蛋白质及其修饰产物在碎屑物质和沉积物中的来源和贡献。氨基酸的一级序列和二级蛋白质结构不仅可以评估主要的输入，还可以评估细菌碳和氮对未知有机池的可能贡献。使用野外收集和实验培养相结合的方法，确定对蛋白质的细微结构修改是否有助于解释有机氮的缺失，这些有机氮没有被量化为总的可水解氨基酸或可提取蛋白质。修饰蛋白质可能是有机氮的重要组成部分，但要么不能被微生物攻击，要么作为降解过程的最终产物存在。蛋白质结构的细微变化可能是理解海洋系统中有机氮(和碳)的保存和长期封存的另一个重要谜题。

ABSTRACTOCE-0352041The importance of the large refractory organic nitrogen pool in the overall nitrogen cycle is well recognized, but its chemical composition and the mechanism(s) responsible for its resistance remain unanswered. Recent work has documented the importance of the amide linkage to organic nitrogen preserved in sediments and soils. The principal investigator on this project and others at the Chesapeake Biological Laboratory have recently shown that proteins can be preserved during early diagenesis and extracted from sediments. The overriding premise of this proposal is that those proteins that are preserved might retain the signal of their original biosynthesis, with only minor modification to their structure. If this is true, then structural identification of individual proteins and mixtures can be used to detail the origins of such proteins and the likely processing which allow their eventual incorporation into sediments. There are therefore two objectives of this project: To adapt current mass spectrometric methods for the analysis of primary protein structure to determine the origin and contributions of proteins and their modified products in detrital material and sediments. The primary sequence of amino acids and secondary protein structure will allow not only the major inputs to be assessed, but also the possible contribution of bacterial carbon and nitrogen to the undefined organic pool.Using a combination of field collections and experimental incubations, to determine if subtle structural modifications to proteins can help account for the missing sink of organic nitrogen that is not quantified as total hydrolysable amino acids or extractable proteins. Modified protein might represent an important fraction of organic nitrogen, but is either not available to microbial attack or exists as an end product of the degradative process. Subtle alterations to protein structure may be another important piece of the puzzle in understanding the preservation and long-term sequestration of organic nitrogen (and carbon) in marine systems.