Control of catecholate siderophore metal preference by fulvic acid

铁载体是由微生物产生的有机分子，作为在铁胁迫条件下获取铁的手段，如在许多土壤和沉积物中发生的。目前认为，这些分子对铁的亲和力和选择性高于土壤溶液中的任何其他元素。由于土壤的复杂性和异质性，铁载体与许多其他成分，最显着的是富里酸，一种普遍存在的有机物质相当大的反应性和重要性。在我们的实验室中，我们已经表明，富里酸与肠杆菌素，一个很好的特点铁载体的显着高亲和力的铁形成密切的协会。更重要的是，我们已经观察到，当富里酸结合肠杆菌素，这种铁载体显示大大减少的亲和力铁和随之而来的增加亲和力铬。这种令人惊讶的金属偏好的逆转在含有铁和铬的矿物溶解期间最为明显，在此期间，铬优先于铁溶解。我们观察到的肠杆菌素金属偏好的富里酸依赖性变化有几个原因。首先，在肠杆菌素和富里酸大量共存的环境中，含铁和铬的矿物质的溶解速率和机制需要重新评估。此外，由于铬可以作为一种必需营养素或作为一种毒素，这取决于其化学形式和浓度，富里酸-肠杆菌素协会的存在可能会影响这种元素的相对可用性和毒性。这项工作的一个更广泛的意义涉及铁和铬，也许还有其他元素的全球地球化学循环，这部分取决于肠杆菌素和富里酸之间复杂的相互作用。此外，我们的研究结果可能会告知无毒和有效的治疗螯合剂的开发和设计，目前在药理学行业的许多工作的重点。本研究旨在发现富里酸在溶解含铁和铬的矿物过程中改变肠杆菌素金属偏好的程度和条件。为此，我们将开发模型，描述铁和铬释放从一个共同的土壤矿物中存在的富里酸肠杆菌素复合物。

Siderophores are organic molecules produced by micro-organisms as a means to acquire iron under conditions of iron stress, as occurs in many soils and sediments. It is currently believed that these molecules have a higher affinity and selectivity for iron than for any other element in soil solution. As a consequence of the complexity and heterogeneity of soils, siderophores occur in association with many other constituents, most notably fulvic acid, a ubiquitous organic material of considerable reactivity and importance. In our laboratory we have shown that fulvic acid forms intimate associations with enterobactin, a well-characterized siderophore of remarkably high affinity for iron. More importantly, we have observed that when fulvic acid is bound to enterobactin, this siderophore displays much-reduced affinity for iron and a concomitant increase in affinity for chromium. This surprising reversal of metal preference is most apparent during the dissolution of minerals containing both iron and chromium, during which chromium is dissolved preferentially over iron. The fulvic acid-dependent change in enterobactin metal preference we observe is of interest for several reasons. First, the rates and mechanisms of dissolution of minerals containing both iron and chromium will need to be reassessed for environments in which enterobactin and fulvic acid occur together in significant quantities. Also, as chromium may serve as either an essential nutrient or as a toxin, depending on its chemical form and concentration, the presence of fulvic acid-enterobactin associations may influence the relative availability and toxicity of this element. A broader implication of this work concerns the global geochemical cycling of iron and chromium, and perhaps other elements, which depend in part on the complex interactions between enterobactin and fulvic acid. Furthermore, results of our investigations may inform development and design of non-toxic and effective therapeutic chelating agents, currently the focus of much work in the pharmacology industry. This research aims to discover the extent and conditions under which fulvic acid modifies enterobactin metal preference during dissolution of minerals containing both iron and chromium. To this end we will develop models describing iron and chromium release from a common soil mineral in the presence of fulvic acid-enterobactin complexes.