碳酸盐矿物选择性催化水解微囊藻毒素的机理研究

Microcystins(MCs) are a group of cyclic heptapeptide hapatotoxins with two free carboxyl groups, which are produced by cyanobateria in water environment and are strong tumor promoter. Generally, oxidation technology was used to destroy the cyclic peptide of MCs to eliminate the toxicity. The catalytic mechanism of selective hydrolysis of MCs on the surface of carbonate mineral (CM) in water is studied, which provides a cheap and efficient pathway to open cyclic peptide and detoxify MCs. First, the element composition and the surface properties was identified by EMPA, XRD, TEM, SEM and BET. Based on the mass law, the hydrolysis kinetic model of MCs and the mineral catalysis types are obtained due to the concentration of MCs and hydrolysis product determined by HPLC, EIS-MS and 1HNMR. On the surface of CM, the structure - activity relationships between element sites/properties and substrate are studied according to the metal ion valence and the concentration of hydroxyl group analyzed by RS and Situ-IR technology. Oxygen-18/deuterium-2 isotope tracer technique is attributable to analyze the formation of carboxyl- and amino group, which helps orient the attack sites by water molecules and the cleavage of peptide bond. The priority hydrolysis in two peptide bonds of R-Glu-Mdha-R and R-MeAsp-Ala-R in MCs cyclic structure will help reveal the selective catalysis mechanism of catalytic CM.

本项目拟研究碳酸盐矿物（Carbonate Mineral, CM）对水中MCs存在的选择性催化水解作用,探索一条经济有效的MCs开环消毒途径.首先采用EMPA,XRD,TEM,SEM,BET测定CM化学组成和表面特性;采用HPLC,EIS-MS和HNMR测定水解过程中MCs和水解产物浓度变化,根据质量守恒定律建立水解动力学模型l来推测CM催化类型;用RS和Situ-IR技术实时跟踪水解过程中CM表面离子价态和羟基浓度变化,分析CM在水解（吸附）MCs过程中CM表面布点元素/表面性质与不同底物分子结构间可能的构效关系;再结合水解产物的氧-18/氘-2同位素示踪技术分析羧基和氨基形成过程中氧\氢归属,定位水分子进攻位点即肽键的断裂位置,推测MC-LR水解机理;在CM催化作用下观察R-D-Glu-Mdha-R和R-D-MeAsp-D-Ala-R两处肽键水解的优先性,推测CM选择性催化水解机理.

通过测试多种碳酸盐矿物对微囊藻毒素（MC-LR）的水解效率，建立了MC-LR水解过程的一级动力学模型，发现黄铁矿、菱铁矿和黏土对MC-LR的水解率分别为66.7%、36.7%和25.3%。通过定性和定量分析MC-LR的水解产物，和对MC-LR分子中七个肽键位点进行了跟踪，我们找到了在水解过程中MC-LR三处易断键位点。采用原位红外光谱仪测定碳酸盐矿物/水界面上MC-LR的吸附模式，发现MC-LR分子酰胺基上H与矿物碳酸根上C=O通过氢键形成环状配合物；正是此特殊吸附位点的存在，使M C-LR顺利水解并具有抗其他有机质干扰的能力，圆满地完成了本研究预期对拟定科学问题的回答：即首次证实碳酸盐矿物通过表面碳酸根离子与MC-LR分子上酰胺键结合形成稳定的环状配合物，从而有效地抵制了水体中其他有机物的干扰，体现出良好的选择性。除了矿物体系外，我们还针对MC-LR的高效降解将体现扩展到金属有机复合物、Bi系催化剂和生物炭等，并对实际废水进行了初步的尝试。