School of Environmental and Chemical Engineering, Shanghai University, Nanchen Road 333, Shanghai 200444, China.
Phys Chem Chem Phys. 2011 Oct 21;13(39):17606-14. doi: 10.1039/c1cp20705a. Epub 2011 Sep 6.
In a mixture of metal ions and complexes, it is difficult to predict ecological risk without understanding the contribution of each metal species to biouptake. For microorganisms, the rate of uptake (internalization flux) has not only a major influence on the total metal flux but also on the bioavailability of the various metal species and their relative contributions to the total flux. In this paper, the microorganism is considered as a consuming interface, which interacts with the metal ion, M, via the Michaelis-Menten boundary conditions. The contribution of each metal complex to the overall metal flux, in relation to its lability, is examined for a number of important boundary parameters (the equilibrium constant K(a) of metal with transport sites, internalization rate constant k(int) and total transport sites concentration {R}(t)). Computations were performed for Cu(II) complexes, in a multicomponent culture medium for microoganisms. For a one-ligand system, results were acquired using rigorous mathematical expressions, whereas approximate expressions, based on the reaction layer approximation (RLA) and rigorous numerical computations (computer codes MHEDYN and FLUXY), were employed for ligand mixtures. Under the condition of ligand excess, as often found in the natural environment, the relative contribution of each metal species to the total flux is shown to be independent of the boundary conditions. This finding has important implications, including an improved basis for relating the analytical signals of dynamic metal speciation sensors to metal bioavailability.
在金属离子和配合物的混合物中，如果不了解每种金属物种对生物摄取的贡献，就很难预测生态风险。对于微生物来说，摄取速率（内化通量）不仅对总金属通量有主要影响，而且对各种金属物种的生物可利用性及其对总通量的相对贡献也有主要影响。在本文中，微生物被视为消耗界面，通过米氏门控边界条件与金属离子 M 相互作用。针对多种重要边界参数（金属与转运位点的平衡常数 K(a)、内化速率常数 k(int)和总转运位点浓度 {R}(t)），考察了每种金属配合物对总金属通量的贡献与其不稳定性的关系。针对微生物的多组分培养介质中的 Cu(II)配合物进行了计算。对于单配体体系，使用严格的数学表达式获得了结果，而对于配体混合物，则使用基于反应层近似（RLA）和严格数值计算（MHEDYN 和 FLUXY 计算机代码）的近似表达式。在配体过剩的条件下，这在自然环境中经常出现，每种金属物种对总通量的相对贡献被证明与边界条件无关。这一发现具有重要意义，包括为将动态金属形态传感器的分析信号与金属生物可利用性相关联提供了更好的基础。
