Methylmercury (MeHg) is one of the most potent neurotoxins. It is produced in nature through the methylation of inorganic divalent mercury (HgII) by phylogenetically diverse anaerobic microbes. The mechanistic understanding of the processes that govern the extent of bacterial export of MeHg, its bioaccumulation, and bio-toxicity depends on accurate quantification of its species, especially its complexation with low molecular mass thiols; organometallic complexes that are difficult to detect and measure in natural conditions. Here, we report the development of a novel analytical method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine 13 MeHg complexes with important thiol compounds which have been observed in the environment and in biological systems. By using online preconcentration via solid phase extraction (SPE), the method offers picomolar (12-530 pM) detection limits, the lowest reported so far for the determination of MeHg compounds. Among three different SPE materials, a weak cation exchange phase showed the best efficiency at a low pH of 2.5. We further report the presence of MeHg-cysteine, MeHg-cysteamine, MeHg-penicillamine, MeHg-cysteinylglycine, and MeHg-glutamylcysteine as the predominant MeHg-thiol complexes in the extracellular milieu of an important HgII methylating bacterium, Geobacter sulfurreducens PCA, exposed to 100 nM of HgII.

中文翻译：

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液相色谱串联质谱法和在线预浓缩法测定低分子量硫醇的甲基汞配合物的皮摩尔含量。

甲基汞（MeHg）是最有效的神经毒素之一。它是通过系统发育的各种厌氧性微生物通过无机二价汞（HgII）的甲基化而自然产生的。对控制甲基汞细菌出口程度，其生物蓄积性和生物毒性的过程的机械理解取决于对其种类的准确定量，特别是其与低分子量硫醇的络合；在自然条件下难以检测和测量的有机金属配合物。在这里，我们报告了一种基于液相色谱串联质谱（LC-MS / MS）的新型分析方法的开发，以确定在环境和生物系统中观察到的13 MeHg与重要硫醇化合物的配合物。通过固相萃取（SPE）在线预浓缩，该方法提供了皮摩尔（12-530 pM）的检测限，这是迄今为止测定MeHg化合物的最低限。在三种不同的SPE材料中，弱阳离子交换相在2.5的低pH值下显示出最佳效率。我们进一步报告了甲基汞-半胱氨酸，甲基汞-半胱胺，甲基汞-青霉胺，甲基汞-半胱氨酸甘氨酸和甲基汞-谷氨酰半胱氨酸作为重要的甲基汞-硫醇复合物在重要的甲基汞-甲基化细菌，暴露于土壤中的硫细菌还原性PCA的细胞外环境中的存在。 100 nM HgII。