Raymond Haran

Gallium-71, carbon-13 and hydrogen-1 NMR studies of the interactions of pyridoxal 5′-phosphate isonicotinyl hydrazone with gallium in aqueous solution

Abstract Ga(III) binding by the new ligand pyridoxal 5′-phosphate isonicotinyl hydrazone (PPL-INH) has been investigated by 71 Ga, 13 C and 1 H NMR. PPL-INH forms a strong complex with gallium. 71 Ga NMR studies are based on the observation of the Ga(OD) − 4 signal, which allows the determination of the 2:1 stoichiometry for the complex. The complexation sites are shown by 13 C NMR. The complex is water-soluble from pH 6 to pH 11, a deprotonated form of the ligand being stabilized by gallium. This work initiates the study of pharmacologic properties of a family of complexes of gallium with hydrazones.

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.

Structural Characterization and Biological Activity of Cupric Complexes of Leu- and Met-enkephalins.

Abstract The formation of cupric ion complexes with leucine-enkephalin and methionine-enkephalin was analysed by 1H NMR, EPR and visible spectroscopy. The biological activity of the complexes was measured by the guinea pig ileum assay and the opiate binding test to rat brain homogenates. Small changes in biological activities are reported in spite of strong binding of the copper ions to the pentapeptides.