链酚胺型配体锌(Ⅱ)配合物模拟碳酸酐酶研究

Research on Zn( II) Complexes with Diaminodiphenol Ligand as Carbonic Anhydrase Model

合成了酚胺型链状配体,N,N’-二(2-羟基苄基)丙二胺(H_2L)及其Zn(Ⅱ)配合物(ZnL),通过元素分析、IR和~1HNMR等手段进行了表征.采用pH电位滴定法,在25±0.1℃,I=0.1mol·dm^(-3)(KNO_3)条件下,测定了配体的质子化常数以及配体与金属离子Zn(Ⅱ)配位反应平衡常数.讨论了配体与金属离子Zn(Ⅱ)的配位情况,得到了配位酚羟基的解离常数.运用分光光度法,在25±0.1℃,I=0.1mol·dm^(-3)(KNO_3)条件下,在pH=5.5～9.0(50mmol·dm^(-3)缓冲溶液)范围内,研究了配合物作为碳酸酐酶模拟物催化对-硝基苯酚乙酸酯(NA)水解动力学,得到了NA酯水解的配合物催化速率常数k_(NP).实验结果表明,ZnHL^+的配位酚羟基的解离常数pK_s为6.83;催化速率常数k_(NP).与pH之间不存在Sigmoidal型曲线关系,而是在pH值中性附近有最大值,ZnHL^+对NA酯水解有很好的催化效果,并且采取双重催化机理,是碳酸酐酶很好的模拟物.

Chain ligand N, N'- bis(2 - hydroxylbenzyl) - propylenediamine (H2L) and its Zn( II ) complex (ZnL) were synthesized and characterized by elemental analysis, IR and 1H NMR. By pHtitration at 25 ± 0. 1℃ and I = 0.1 mol dm-3 (KNO3), protonation constants of the ligand and equilibria constants of Zn( II ) complexation with the ligand have been determined. Modes of the ligand coordination to Zn( II ) were discussed, and the dissociation constant for the phenoxyl in complex ZnHL+ was obtained . The kinetics of p - nitrophenyl acetate (NA) hydrolysis catalyzed by the complexes ascarbonic anhydrase models was determined spectrophotometrically at 25 ± 0.1℃ and I = 0.1 mol dm-3(KNO3) in 10% (v/v) CH3CN at pH 5. 5 ~ 9. 0 (50mmol·dm-3 buffers), and the second - rate constants for NA hydrolysis were obtained. The experimental results indicate that the dissociation constant pKa value for the phenoxyl in complex ZnHL+ is 6.83. The pH - kNP profile does not exhibit a Sigmoidal curve and the kNP reaches a maximum point around,neutral pH. The complex ZnHL+ has very strong catalytic ability around neutral pH following the double - catalysis mechanism, and therefore is a good carbonic anhydrase model.