Collaborative Research: Characterization of Iron Binding Organic Ligands in Seawater

铁是许多关键生化过程的必需元素，包括呼吸、固氮、硝酸盐还原和叶绿素生物合成。铁形态测量表明，99%的溶解铁与有机配体络合，形成非常强的铁-有机络合物，有助于稳定海水中的铁（III），将其浓度提高到维持微生物生长的水平。然而，这些在海洋铁循环中起重要作用的配体的组成在很大程度上仍然未知。来自伍兹霍尔海洋研究所和南加州大学的科学家们提议对天然存在的铁结合配体进行表征。具体来说，研究人员计划从非常大体积（104 L）的样品中收集强铁结合配体，并进行详细的光谱分析（质谱和核磁共振光谱），以确定配体的分布、官能团特征，并最终确定主要配体的结构。北太平洋的初步结果表明，我们的收集方案回收了60%的铁配体配合物和25-30%的总配体。在强螯合剂（EDTA， DTPA， DFB）存在的情况下，配体提取物（Kcond L/Fe' 1012）和竞争同位素（55Fe和Ga (III)）标记的条件稳定性常数的测量使我们能够仅针对强配体进行光谱分析。表征天然存在的铁结合配体将更好地了解海水中的铁形态，并补充正在进行的铁配体在纯培养物和海洋浮游生物混合组合中的生物利用度研究。至于更广泛的影响，富布赖特博士后学者将参与研究。作为该项目的一部分，南加州大学的一名研究生将得到支持和培训。作为该项目的一部分，一名高中生也将在伍兹霍尔海洋研究所得到支持和培训。此外，预计通过伍兹霍尔海洋学研究所暑期学生奖学金计划支持的本科生将参与这项研究。

OCE-0751733OCE-0751822Iron is an essential element in many key biochemical processes, including respiration, nitrogen fixation, nitrate reduction, and chlorophyll biosynthesis. Iron speciation measurements show that 99% of dissolved iron is complexed by organic ligands that form very strong ferri-organic complexes that help stabilize Fe(III) in seawater, increasing its concentration to levels that can sustain microbial growth. However, the composition of these ligands that play an important role in the marine iron cycle remains largely unknown. Scientists from Woods Hole Oceanographic Institution and the University of Southern California propose to characterize the naturally occurring iron-binding ligands. Specifically, the investigators plan to collect strong iron-binding ligands from very large volume (104 L) samples and perform detailed spectral analysis (mass spectrometry and nuclear magnetic resonance spectroscopy) to determine ligand distributions, functional group characteristics, and ultimately the structures of major ligands. Preliminary results from the North Pacific Ocean show our collection protocol recovers 60% of Fe-ligand complexes and 25-30% of total ligands. Measured conditional stability constants of the ligand extract (Kcond L/Fe' 1012) and competitive isotopic (55Fe and Ga (III)) labeling in the presence of strong chelators (EDTA, DTPA, DFB) allows us to target only strong ligands for spectral analysis. Characterization of naturally occurring iron binding ligands would provide a better understanding of iron speciation in seawater, and complement on-going studies of Fe-ligand bioavailability in pure cultures and mixed assemblages of marine plankton.As regards broader impacts, a Fulbright postdoctoral scholar would participate in the research. One graduate student from the University of Southern California would be supported and trained as part of this project. One high school student would also be supported and trained as part of this project at the Woods Hole Oceanographic Institution. In addition, it is anticipated that undergraduate students supported via the Woods Hole Oceanographic Institution summer student fellowship program would participate in the study.