Laboratoire de Biochimie, CNRS, École Polytechnique, Palaiseau, France.
PLoS One. 2013;8(1):e54353. doi: 10.1371/journal.pone.0054353. Epub 2013 Jan 14.
Inert metal-selenide colloids are found in animals. They are believed to afford cross-protection against the toxicities of both metals and selenocompounds. Here, the toxicities of metal salt and sodium selenide mixtures were systematically studied using the death rate of Saccharomyces cerevisiae cells as an indicator. In parallel, the abilities of these mixtures to produce colloids were assessed. Studied metal cations could be classified in three groups: (i) metal ions that protect cells against selenium toxicity and form insoluble colloids with selenide (Ag⁺, Cd²⁺, Cu²⁺, Hg²⁺, Pb²⁺ and Zn²⁺), (ii) metal ions which protect cells by producing insoluble metal-selenide complexes and by catalyzing hydrogen selenide oxidation in the presence of dioxygen (Co²⁺ and Ni²⁺) and, finally, (iii) metal ions which do not afford protection and do not interact (Ca²⁺, Mg²⁺, Mn²⁺) or weakly interact (Fe²⁺) with selenide under the assayed conditions. When occurring, the insoluble complexes formed from divalent metal ions and selenide contained equimolar amounts of metal and selenium atoms. With the monovalent silver ion, the complex contained two silver atoms per selenium atom. Next, because selenides are compounds prone to oxidation, the stabilities of the above colloids were evaluated under oxidizing conditions. 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), the reduction of which can be optically followed, was used to promote selenide oxidation. Complexes with cadmium, copper, lead, mercury or silver resisted dissolution by DTNB treatment over several hours. With nickel and cobalt, partial oxidation by DTNB occurred. On the other hand, when starting from ZnSe or FeSe complexes, full decompositions were obtained within a few tens of minutes. The above properties possibly explain why ZnSe and FeSe nanoparticles were not detected in animals exposed to selenocompounds.
惰性金属硒化物胶体存在于动物体内。人们认为它们能够为金属和硒化合物的毒性提供交叉保护。在这里，我们使用酿酒酵母细胞死亡率作为指标，系统地研究了金属盐和硒化钠混合物的毒性。同时，评估了这些混合物产生胶体的能力。研究的金属阳离子可以分为三类：（i）能够保护细胞免受硒毒性并与硒化物形成不溶性胶体的金属离子（Ag⁺、Cd²⁺、Cu²⁺、Hg²⁺、Pb²⁺和 Zn²⁺），（ii）通过生成不溶性金属硒化物配合物和在氧气存在下催化硒化氢氧化来保护细胞的金属离子（Co²⁺和 Ni²⁺），最后，（iii）在测试条件下，不能提供保护且不与硒化物相互作用（Ca²⁺、Mg²⁺、Mn²⁺）或弱相互作用（Fe²⁺）的金属离子。当发生时，二价金属离子和硒化物形成的不溶性配合物含有等摩尔量的金属和硒原子。对于单价银离子，配合物中每个硒原子含有两个银原子。接下来，由于硒化物是易于氧化的化合物，因此在氧化条件下评估了上述胶体的稳定性。5,5'-二硫代双（2-硝基苯甲酸）（DTNB），其还原可以通过光学方法跟踪，用于促进硒化物氧化。含有镉、铜、铅、汞或银的配合物在 DTNB 处理数小时后仍不溶解。对于镍和钴，发生部分氧化。另一方面，当从 ZnSe 或 FeSe 配合物开始时，在几十分钟内就会完全分解。上述性质可能解释了为什么在暴露于硒化合物的动物中未检测到 ZnSe 和 FeSe 纳米颗粒。
