Lins Roberto D, Vorpagel Erich R, Guglielmi Matteo, Straatsma T P
Computational Biology and Bioinformatics, and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
Biomacromolecules. 2008 Jan;9(1):29-35. doi: 10.1021/bm700609r. Epub 2007 Dec 8.
Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies. The outer membranes of Gram-negative microbes are highly nonsymmetric and exhibit a significant electrostatic potential gradient across the membrane. This gradient has a significant effect on the uptake and transport of charged and dipolar compounds. However, the effectiveness of microbial systems for environmental remediation will depend strongly on specific properties that determine the uptake of targeted contaminants by a particular cell wall. To aid in the design of microbial remediation technologies, knowledge of the factors that determine the affinity of a particular bacterial outer membrane for the most common ionic species found in contaminated soils and groundwater is of great importance. Using our previously developed model for the lipopolysaccharide (LPS) membrane of Pseudomonas aeruginosa, this work presents the potentials of mean force as the estimate of the free energy profile for uptake of sodium, calcium, chloride, uranyl ions, and a water molecule by the bacterial LPS membrane. A compatible classical parameter set for uranyl has been developed and validated. Results show that the uptake of uranyl is energetically a favorable process relative to the other ions studied. At neutral pH, this nuclide is shown to be retained on the surface of the LPS membrane through chelation with the carboxyl and hydroxyl groups located in the outer core.
重金属环境污染物无法被销毁，而是需要进行封存，最好以浓缩形式，以固体或固定形式进行回收或最终处置。微生物能够吸收并将高浓度的污染金属，包括铀和钚等放射性金属，沉积到其细胞壁中。因此，这些微生物系统作为潜在环境生物修复技术的基础备受关注。革兰氏阴性菌的外膜高度不对称，膜两侧存在显著的静电势梯度。这种梯度对带电和偶极化合物的吸收和运输有显著影响。然而，微生物系统用于环境修复的有效性将很大程度上取决于特定的性质，这些性质决定了特定细胞壁对目标污染物的吸收。为了辅助微生物修复技术的设计，了解决定特定细菌外膜对污染土壤和地下水中最常见离子种类亲和力的因素非常重要。利用我们之前开发的铜绿假单胞菌脂多糖（LPS）膜模型，这项工作给出了平均力势，作为细菌LPS膜对钠、钙、氯、铀酰离子和水分子吸收的自由能分布估计。已经开发并验证了一套适用于铀酰的经典参数集。结果表明，相对于所研究的其他离子，铀酰的吸收在能量上是一个有利的过程。在中性pH值下，这种核素通过与位于外核的羧基和羟基螯合而保留在LPS膜表面。
