铕与醛糖及铕与D─核糖、L─氨基酸络合作用的伏安法研究

Studies on the Voltammetric Behavior of Eu￣(3+)-aldopentose and Eu￣(3+)-D-ribose-L-amino Acids Complexes

Ｅｕ（３＋）在ＨＡｃ－ＮａＡｃ（ｐＨ４．６）溶液中与五碳醛糖有弱的络合作用，用循环伏安法和微分脉冲极谱可以观察到Ｄ－核糖，Ｄ－阿拉伯糖，Ｄ－木糖对Ｅｕ（３＋）还原波形的络合影响，使还原和氧化过程变得较为可逆，其中Ｄ－核糖最为明显，而来苏糖无影响．Ｅｕ（３＋）与氨基酸在相同实验条件下有络合作用，且在汞电极上有吸附现象，因此分别加入Ｌ－苯丙氨酸、Ｌ－组氨酸和Ｌ－蛋氨酸等，进一步改善了Ｅｕ（３＋）的波形而接近于可逆氧化－还原过程，其中以Ｅｕ（３＋）－Ｄ－核糖－Ｌ－苯丙氨酸最明确。绘出了在电极表面形成三元络合物的示意图。

The complexing ability of various cyclitols and aldoses with some metal ions has been studied that aldoses having an ax-eq-ax sequence of three hydroxy groups of their tautomeric species can provide good sites for complex formation with metal ions. Therefore D-ribose, D-lyxose, D-arabinose and D-xylose are chosen as the ligands for the complexation of Eu￣(3+) in the present voltammetric study. It has been proved that the formation of the mixed ligand complex is favorable in biological systems, so some L-amino acids were used as the secondary ligands for the formation of ternary complex of Eu￣(3+) in HAc-NaAc solution. Eu￣(3+)-D-aldopentose system : The redox process of Eu￣(3+) becomes more reversible in the presense of aldopentose. The decrese order of △Ep is D-ribose> D-lyxose>D-arabinose , while D-xylose has no effect. Eu￣(3+)-D-ribose-L-amino acids system : The addition of both D-ribose and L-phenylalanine results in obvious increase in current and decrease in half-peak width. The effect is synergic and applies also for other amino acids such as histidine, methionine and lysine.The ternary complex of Eu3+-D-ribose-L-phenylalanine formed on the mercury surface is responsible for quasi-reversible reduction of Eu￣(3+) in acetate solution at pH>3. 3. The schematic picture of the ternary complex adsorbed on the surface is proposed.