HClO对贻贝粘附单元DOPA氧化的理论研究

Theoretical study of the oxidizing mechanism for the reaction of HClO and adhesive unit DOPA in the mussel

采用量子化学密度泛函理论(DFT)研究贻贝粘附单元DOPA(3,4-二羟基苯丙氨酸)的结构与性质,得分子的几何构型、原子电荷分布、反应活性及热力学等参数,表明:DOPA苯环易与HClO(次氯酸)发生亲电取代反应(1),生成3-氯-4,5-二羟基苯丙氨酸,阻碍生成贻贝内超强粘附单元DOPA二联体,降低粘附蛋白间粘性;DOPA侧链易与HClO发生亲电亲核反应(2),促使DOPA侧链的断裂,降低粘附蛋白内粘性;在相同温度下,反应(1)和反应(2)的ΔG<0,且ΔG(1)<ΔG(2),反应(1)较易发生。

By using density functional theory （DFT） quantum mechanics procedure, the structure and properties of DOPA were theoretically studied. The geometrical optimization, atomic electric charges, activation of reaction and thermodynamics parameters were obtained. The calculation shows that benzene ring in DOPA tends to have electrophonic attacking substitution reaction （ 1 ） with HClO and the product 3-chlorine-4, 5-dihydroxyphenylalanine hinders the formulation of conjuncted DOPA - DOPA which is the superstrongly adhesive unit in mussels, and then the stickiness among mussel adhesive proteins reduced; on the other hand, the DOPA side chain is easy to have electrophilic and nucleophilic attacking reaction （2） with HClO, which leads to the DOPA side chains broken down, so the stickiness inside mussel adhesive protein also reduced. The calculation of thermodynamics properties indicates AG 〈 0 for reaction （ 1 ） and （2）, and under the same temperature AG （ 1 ） 〈 AG （2）, reaction （ 1 ） easily occurred.