Two new functionalized cyclodipeptides have been synthesized with the aim of obtaining a good model of superoxide dismutase. Better to mimic the active site of this metalloenzyme, these two compounds have been designed to allow a great co-ordination flexibility. Copper(II) complexes with cyclo(-L-aspartyl-L-aspartyl-) or cyclo(-L-glutamyl-L-glutamyl-)bis(histamine)(L) have been thermodynamically and spectroscopically characterized and their antioxidant activity tested against enzymatically generated O2–. Taking into account the speciation of the system, it has been determined that the more active species against O2– is the [CuL2]2+ complex. Electron spin resonance measurements suggest for this species the presence of four imidazole nitrogen atoms in a slightly tetrahedrally distorted co-ordination plane. The [CuLH–2] complex species also possesses four-nitrogen co-ordination involving two deprotonated peptide nitrogen atoms. The complex [CuL2]2+ showed the highest antioxidant activity and reasons for this behaviour are proposed on the basis of spectroscopic and voltammetric data.
为了获得超氧化物歧化酶的良好模型,我们合成了两种新的功能化环二肽。为了更好地模拟这种
金属酶的活性位点,这两种化合物的设计具有极大的配位灵活性。
铜(II)与环(-L-天冬
氨酰-L-天冬
氨酰-)或环(-L-谷
氨酰-L-谷
氨酰-)双(
组胺)(L)的配合物已经过热力学和光谱学表征,并测试了它们对酶生成的 O2- 的抗氧化活性。考虑到该体系的种类,已确定对 O2- 更有活性的种类是[Cu
L2]2+ 复合物。电子自旋共振测量结果表明,该复合物在一个略呈四面体畸变的配位平面中存在四个
咪唑氮原子。CuLH-2]复合物也具有四个氮原子配位,其中包括两个去质子化的肽氮原子。[Cu
L2]2+复合物显示出最高的抗氧化活性,根据光谱和伏安数据提出了这种行为的原因。