Carbonate Radical Oxidation of Cylindrospermopsin (Cyanotoxin): Kinetic Studies and Mechanistic Consideration
Carbonate Radical Oxidation of Cylindrospermopsin (Cyanotoxin): Kinetic Studies and Mechanistic Consideration
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DOI：
10.1021/acs.est.0c03404
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发表时间：
2020-08-18
影响因子：
11.4
通讯作者：
Song, Weihua
中科院分区：
文献类型：
--
作者：
Hao, Zhenyu;Ma, Jianzhong;Song, Weihua
草履虫毒素（CYN）是一种常见于沃茨中的重要蓝藻毒素。我们报告了详细的动力学和途径的反应CYN与碳酸根（CO 3中心点-）。以CO_3为中心的中性和去质子化CYN的速率常数分别为（1.2 ± 0.7）× 10 ~（7）M ~（-1）S ~（-1）和（3.0 ± 0.4）× 10 ~（8）M ~（-1）S ~（-1）。通过高分辨质谱鉴定了CO 3中心点-氧化CYN的转化产物，说明胍和桥连羟基部分是CO 3中心点-攻击的主要部分。因此，三个转化途径，包括羟甲基尿嘧啶部分的裂解，羟基化，和桥连羟基的氧化，提出了CO 3中心点氧化CYN。此外，本研究还发现溶解性有机物（DOM）通过抑制氧化中间产物的转化而降低了CYN的转化速率。最后，在阳光照射的表面沃茨和高级氧化过程（AOPs）中，CO 3中心点-在CYN降解中的作用进行了估计，表明在非酸性环境相关条件下，CO 3中心点-在CYN衰减中发挥了重要作用。本研究所获得的动力学参数和产物信息对AOPs的应用和预测CYN的环境归趋具有重要意义。
Cylindrospermopsin (CYN) is one of the most important cyanobacterial toxins frequently found in surface waters. We reported the detailed kinetics and pathways for the reaction of CYN with carbonate radicals (CO3 center dot-). The rate constants of neutral and deprotonated CYN with CO3 center dot- were found to be (1.2 +/- 0.7) X 10(7) M-1 S-1 and (3.0 +/- 0.4) X 10(8) M-1 s(-1), respectively. The transformation products for the oxidation of CYN by CO3 center dot- were identified by high-resolution mass spectrometry, illustrating that the guanidine and bridged hydroxyl portions were the primary moieties attacked by CO3 center dot-. Thus, three transformation pathways, including cleavage of the hydroxymethyluracil moiety, hydroxylation, and oxidation of the bridged hydroxyl group, are proposed for the CO3 center dot- oxidation of CYN. Moreover, this study reported that dissolved organic matter (DOM) reduced the transformation rate of CYN by inhibiting the transformation of oxidation intermediates. Finally, the role of CO3 center dot- in CYN degradation was estimated in both sunlit surface waters and advanced oxidation processes (AOPs), demonstrating that CO3 center dot- played an important role in CYN attenuation under nonacidic environmentally relevant conditions. The kinetic parameters and product information obtained in this study will be of considerable interest for the application of AOPs and predicting the environmental fate of CYN.