丙氨酸二元和三元配合物的pH电位法研究

本文报导了用pH电位法在温度为37±0.1℃和离子强度为150mM/dm³下研究了丙氨酸与铜、锌、镍、镉的二元和三元配合物稳定常数,并确定了各体系中配合物粒子的正确组成.ΔlgK和lgX值表明混合配合物比较稳定。配位离子分布图指出在生理条件下,这些配合物主要是以中性配合物的形式存在。这对于金属离子的透膜传输有重要意义。

Studies on Binary and Ternary Complexes of DL-α-Alanine by pH Potentiometric Titration

The binary and ternary stability constants of DL-α-Alaninc with Cu(Ⅱ),Zn(Ⅱ),Ni(Ⅱ) and Cd(Ⅱ) were determined by pHpolcntiometric titration at 37±0.1℃ and ionic strength 150mM/dm³.Potentiomeinc data were treated with ZPLOT,MAGEC,MINIQUADand ESTAprograms.The compositions of complex species were ascertained in the complex equilibriums by selection of different chemical models.The lgKand lgXvalues indicate that the complexes with mixed li-gands were obviously more stable than the simple binary systems especially in the zinc-alaninate-histidinale-proton system.Distribution curves of the complex species show the continuity of stepwise cotnplexing in the formation of complexes.At physiological pHregion these complexes,except cadium system,existed mainly in the form of neutral complexes which have biological significance in the transfer of metal ons acrossing the membrane.