The binding of aluminium to [Leu5]-enkephalin. An investigation using 1H, 13C and 27Al NMR spectroscopy.

The binding of aluminium ion to [Leu5]-enkephalin has been investigated by 1H, 13C and 27Al NMR spectroscopy in dimethyl sulphoxide solution at different peptide/metal ratio. Analysis of the spectra suggests that Al3+ binds at two metal-binding sites. The binding of Al3+ at the first site involves the Tyr1CO, and Leu5COO- groups to give a 2:1 species in a tetracoordinated structure; whereas the binding of Al3+ at the second site utilizes the NH2 terminal groups of the tyrosine moiety in a 2:2 species. 27Al chemical shift values strongly suggest that the second type of aluminium atom displays an octahedral environment. On this basis, we discuss our data in terms of the coordination of aluminium with [Leu5]-enkephalin.