Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment
Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment
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DOI：
10.1021/jacs.1c07103
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发表时间：
2021-09-29
影响因子：
15
通讯作者：
Cotruvo, Joseph A., Jr.
中科院分区：
文献类型：
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作者：
Deblonde, Gauthier J-P;Mattocks, Joseph A.;Cotruvo, Joseph A., Jr.
人为放射性核素，包括Am和Cu等长寿命的重放射性元素，是核废料管理的主要长期挑战。这些废物可能排放到环境中，需要了解它们与自然界中存在的生物地质化合物的相互作用。在这里，我们描述了重元素Am~(3+)和Cm~(3+)与天然的镧系元素结合蛋白兰摩素(LAMM)之间的相互作用。兰姆是由甲基营养细菌大量产生的，包括在环境中广泛存在的甲烷绿僵菌。我们测定了AM3+-蛋白质络合物的第一稳定常数(Am(3)Lanm)，并用Cm(3)Lanm进行了验证，结果表明其亲和力比离子半径最接近的稀土离子Nd3+和Sm3+的亲和力高出近5倍，使Lanm成为已知的最强的重鳗系元素结合蛋白。该蛋白质对Am-243‘S子体核素NP-239的高选择性使实验室规模的鳗系元素分离成为可能，并为环境中这些元素的潜在蛋白质驱动动员提供了洞察力。Cm~(3+)-La~(3+)络合物的发光性质和Gd~(3+)-La~(3+)的核磁共振研究表明，在一定的金属离子半径范围内，兰摩尔素结合的f-元素具有两个配位的溶剂分子。最后，我们证明了在广泛的环境相关条件下，兰调素有效地胜过去铁胺B，去铁胺B是一种异羟甲酸铁载体，以前被认为在三价鳗系元素的迁移性中起重要作用。这些结果表明，天然的镧系元素结合蛋白，如兰姆素，可能在环境中放线元素的形态和迁移性方面发挥重要作用；这也表明，基于蛋白质的生物技术可能在元素修复、检测和分离方面提供一个新的前沿。
Anthropogenic radionuclides, including long-lived heavy actinides such as americium and curium, represent the primary long-term challenge for management of nuclear waste. The potential release of these wastes into the environment necessitates understanding their interactions with biogeochemical compounds present in nature. Here, we characterize the interactions between the heavy actinides, Am3+ and Cm3+, and the natural lanthanide-binding protein, lanmodulin (LanM). LanM is produced abundantly by methylotrophic bacteria, including Methylorubrum extorquens, that are widespread in the environment. We determine the first stability constant for an Am3+-protein complex (Am(3)LanM) and confirm the results with Cm(3)LanM, indicating a similar to 5-fold higher affinity than that for lanthanides with most similar ionic radius, Nd3+ and Sm3+, and making LanM the strongest known heavy actinide-binding protein. The protein's high selectivity over Am-243's daughter nuclide Np-239 enables lab-scale actinide-actinide separations as well as provides insight into potential protein-driven mobilization for these actinides in the environment. The luminescence properties of the Cm3+-LanM complex, and NMR studies of Gd3+-LanM, reveal that lanmodulin-bound f-elements possess two coordinated solvent molecules across a range of metal ionic radii. Finally, we show under a wide range of environmentally relevant conditions that lanmodulin effectively outcompetes desferrioxamine B, a hydroxamate siderophore previously proposed to be important in trivalent actinide mobility. These results suggest that natural lanthanide-binding proteins such as lanmodulin may play important roles in speciation and mobility of actinides in the environment; it also suggests that protein-based biotechnologies may provide a new frontier in actinide remediation, detection, and separations.