Biomimetic Trihydroxamate Ligands and Triple Stranded Helices: Iron(III) Coordination Mechanism
Résumé
Ferrioxamines and ferrichromes are microbial iron(III) trihydroxamate binders that facilitate iron(III) through biological membranes. Chiral linear and tripod-like trihydroxamate ligands having carbon or amine as anchors have been synthetized. In an attempt to establish a possible relationship between structure , iron(III) coordination properties and biological activity, we undertook a physicochemical study of the complexes. Specifically, we examined the iron(III) release kinetics of the complexes with the scavenging CDTA as sensitive indicators of their coordination properties and subtle changes in the lipophilicity and steric hindrance of the peptidic chains bearing the coordination sites. Kinetic results obtained for the ferrichrome analogues are in perfect agreement with the empirical force field calculated structures of the complexes and their biological activity. The elongation of the artificial tripod-like ferrichrome analogues by a second ion binding cavity opens the way to ditopic triple stranded helices. In order to obtain information about the formation mechanism of the helical iron(III) complexes, electrospray mass , spectrometric, UV-visible absorption spectrophotometric and kinetic measurements were carried out and will be presented
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