Structure-based differences between the metal ion selectivity of two siderophores desferrioxamine B (DFB) and desferricoprogen (DFC): why DFC is much better Pb(II) sequestering agent than DFB?

Complexation of desferrioxamine B (DFB) and desferricoprogen (DFC) with Cd(II) and Pb(II) toxic ions as well as complexation of DFC with Ca(II) and Mg(II) essential metals have been investigated and the results have been compared to those with other metal ions. The two siderophores have moderate Cd(II)-binding ability, but both, and especially DFC, bind Pb(II) in high stability complexes. Surprisingly, significant differences exist between Pb(II)-complexation of DFB and DFC.

Interaction of imidazole containing hydroxamic acids with Fe(III): hydroxamate versus imidazole coordination of the ligands.

Solution equilibrium studies on Fe(III) complexes formed with imidazole-4-carbohydroxamic acid (Im-4-Cha), N-Me-imidazole-4-carbohydroxamic acid (N-Me-Im-4-Cha), imidazole-4-acetohydroxamic acid (Im-4-Aha), and histidinehydroxamic acid (Hisha) have been performed by using pH-potentiometry, UV-visible spectrophotometry, EPR, ESI-MS, and H1-NMR methods. All of the obtained results demonstrate that the imidazole moiety is able to play an important role very often in the interaction with Fe(III), even if this metal ion prefers the hydroxamate chelates very much. If the imidazole moiety is in alpha-position to the hydroxamic one (Im-4-Cha and N-Me-Im-4-Cha) its coordination to the metal ion is indicated unambiguously by our results.

Pb(II)-binding capability of aminohydroxamic acids: primary hydroxamic acid derivatives of alpha-amino acids as possible sequestering agents for Pb(II).

Complexes of aminohydroxamic acids, D,L-alpha-alaninehydroxamic acid (alpha-Alaha), sarcosinehydroxamic acid (Sarha), D,L-N-methyl-alpha-alaninehydroxamic acid (N-Me-alpha-Alaha), beta-alaninehydroxamic (beta-Alaha), L-aspartic acid-beta-hydroxamic acid (Asp-beta-ha), L-glutamic acid-gamma-hydroxamic acid (Glu-gamma-ha) and L-histidinehydroxamic acid (Hisha) with lead(II) in aqueous solution were studied by pH-potentiometric, 1H NMR and electrospray ionization mass spectrometric (ESI MS) methods. The results were compared to those of a simple monohydroxamic acid, acetohydroxamic acid and the effects of the amino group, hydroxamate-N, as well as, additional side chain donors on the co-ordination mode and on the stability of the complexes formed were evaluated. It was found that the amino nitrogen atom situating in beta- or in gamma-position (beta-Alaha, Asp-beta-ha, Glu-gamma-ha) does not co-ordinate to Pb(II), only hydroxamate type chelates are formed before the hydrolytic processes.

Interaction of desferrioxamine B (DFB) model dihydroxamic acids with some essential and toxic metal(II) ions: effects of the structure and length of connecting chains on the metal ion selectivity.

Complexation of desferrioxamine B (DFB) model dihydroxamic acids (HO(CH3)NCO(CH2)xCONH(CH2)yCON(CH3)OH where x = 2, 3, y = 5, 4, 3, 2, and the compounds are abbreviated as 2,5-DIHA, 2,4-DIHA, 2,3-DIHA, 2,2-DIHA, 3,4-DIHA and 3,3-DIHA, respectively) with Cu(II), Ni(II), Zn(II), Pb(II) and Cd(II) was studied by pH-potentiometric and spectroscopic (UV-VIS, NMR and ESI-MS) techniques. The effects of the position of the peptide group, the chain length and the geometry on the stability and stoichiometry of the complexes formed were evaluated. It was concluded that metal ions preferring regular octahedral geometry in their complexes form the most stable bis-chelated mononuclear complexes, [ML], with 2,5-DIHA having the same connecting chain structure and length as those of DFB.