Penta-glycine copper(II) complexes in slightly alkaline solutions

• Copper ligated to short peptides is penta-coordinated with an axial H2O.
• The axial coordinated water has a relatively low pKa.
• The copper remains bound to the terminal amine though the nickel does not.

The kinetics of the reaction of CuII(GGG), CuII(GGGGG) and CuII(GGGGS), where G = glycine and S = sarcosine, with 4-nitrophenyl-acetate were measured. The results point out that at pH 9.0 hydroxide is an axial, or equatorial ligand to a significant amount of these complexes. The source of the different mechanisms of reaction of the analogous nickel complexes is attributed to the axial water ligand of the copper complexes. The biological implications of axial hydroxide binding to copper peptides is discussed.

At pH 9.0 hydroxide is an axial, or equatorial ligand to a significant amount of CuII(GGG), CuII(GGGGG) and CuII(GGGGS).Figure optionsDownload as PowerPoint slide