Kinetics and Mechanism of Iron-Ligand Exchange Reactions in the Presence of Surfactants and/or Crown Ethers

该项目的主要目标是阐明微生物中铁在适当的时间和地点从其极其稳定的载体中释放出来的机制。模型实验将使用胶束来探测水/细胞界面对铁载体和其他多齿螯合剂稳定铁的可能影响。将测试水/胶束界面对铁/配体交换动力学的影响，例如亲水性铁载体铁胺B和胶束结合的疏水螯合剂苯甲羟肟酸。在一些实验中，菲罗啉也会加入到胶束中，因为初步数据表明，菲罗啉通过氧化还原机制加速铁/配体交换进入胶束伪相。为了评估铁（III）配体解离动力学的第二配位壳效应，将研究水溶液中的超分子组装。疏水冠醚可以使这些超分子组合在胶束“表面”上形成。这些组合物可用作细胞表面受体复合物的模型。这些超分子组合（例如，铁胺b -冠醚-表面活性剂）内配体交换的动力学以及三元配合物形成对这些动力学的影响将被测量。在化学学部无机、生物无机和有机金属项目的这个项目中，杜克大学的Alvin L. Crumbliss博士将模拟铁在适当的时间和地点从微生物中释放出来的方式。细菌中含有结合和运输铁的分子，这些分子非常有效，有些被用作螯合治疗的药物。这些生物无机实验的结果将增强我们对微生物铁转运机制和金属提取过程相关机制的理解。

The principal goal in this project is to elucidate the mechanism in microbes whereby iron is released from its extremely stable carrier at the appropriate time and location. Model experiments which use micelles designed to probe possible effects of the aqueous/cell interface on the labilization of iron from siderophores and other polydentate chelators will be performed. The influence of the aqueous/micelle interface on the kinetics of iron/ligand exchange between, for example, the hydrophilic siderophore ferrioxamine B and a micelle bound hydrophobic chelator, benzohydroxamic acid, will be tested. Phenanthroline will also be incorporated into the micelle in some experiments, as preliminary data show that phenanthroline accelerates iron/ligand exchange into the micellar pseudo-phase via a redox mechanism. Supramolecular assemblies in aqueous solution will be investigated in order to evaluate second coordination shell effects on iron(III)-ligand dissociation kinetics. Hydrophobic crown ethers may permit these supra- molecular assemblies to form on micelle "surfaces". These assemblies may be used as models for cell surface receptor complexes. The kinetics of ligand exchange within these supra- molecular assemblies (e.g., ferrioxamine B-crown ether- surfactant) and the influence that ternary complex formation has on these kinetics will be measured. %%% In this project in the Inorganic, Bioinorganic, and Organo- metallic Program of the Chemistry Division, Dr. Alvin L. Crumbliss of Duke University will model the way in which iron is released in microbes at the appropriate time and location. Bacteria contain molecules which bind and transport iron so efficiently that some are used as drugs in chelation therapy. The results of these bioinorganic experiments will enhance our understanding of microbial iron transport mechanisms and mechanisms related to metal extraction processes.