锌(Ⅱ)-氨基酸配合物分子内配体间疏水作用

应用 p H电位滴定法研究了配合物 Zn( Aa) 2 Aa-=L- val(缬氨酸根 ) ,L- phe(苯丙氨酸根 ) ,L- trp(色氨酸根 ) ,L- tyr(酪氨酸根 ) ]在水和 2 0 %、40 %及 60 %二氧六环 /水溶液中的稳定性 t=2 5℃ ,c=0 .1 mol/L Na Cl O4]。配合物 Zn( Aa) 2 相对于母体配合物 Zn( Aa) + 稳定性用Δlog K=log KZn( Aa)Zn( Aa) 2 - log KZn Zn( Aa) 表示。结果表明 :与 L-丙氨酸 ( L- ala)配合物 Zn( L- ala) 2 相比 ,所有这些氨基酸配合物 Zn( Aa) 2 均具有相对较大的 Δlog K值 ,表明这些配合物分子内存在着额外的稳定化作用。这种稳定性化作用可能主要归因于配合物分子内氨基酸侧链之间的疏水作用 ,并且这种作用随着氨基酸侧链结构及溶剂极性变化而变化

Studies on the Intramolecular Ligand-ligand Hydrophobic Interactions of Complexes of Zn(Ⅱ)ion with Amino Acids

Stability constants of complexes Zn(Aa) 2 have been determined by pH potentiometric titrations in water, 20%, 40% and 60% dioxane-water solutions where Aa -=L-valinate, L-tryptophanate, L-phenylalaninate and L-tyrosinate (t=25℃, c=0.1 mol/L NaClO 4). The stability of complexes Zn(Aa) 2 relative to their parent complexes Zn(Aa) + is defined as ΔlogK=log Zn(Aa) Zn(Aa) 2-logK Zn Zn(Aa). The results show that compared with complex Zn(L-alaninate) 2 the complexes with the amino acids have larger ΔlogK values, indicating that there are extra stabilizing effects in the complexes. This may be mainly attributed to the intramolecular hydrophobic interaction between the side chains of the two amino acids in the complexes. In addition, this interaction varies with the nature of the side chains of the amino acids and the solvent polarity.