title: Vesicles to concentrate iron in low-iron media: an attempt to mimic marine siderophores.
abstract: Amphiphilic catechol-type iron chelators were studied with the aim of mimicking the properties of marine bacterial siderophores. The Fe(III) complexation constants and aqueous solution speciation of L(S10), a sulfonated catechol unit that has a C(10) lipophilic carbon chain connected by an amide linkage, were determined by spectrophotometric titration. The calculated value of pFe3+ is 18.1 at pH 7.4. Cryogenic transmission electron microscopy showed that the tris(catecholate) ferric complex formed at physiological pH initially assembles into micelles, in which the catecholate-iron units stay on the exterior of the micelle. The average diameter of these micelles was estimated to be 4.2 nm. The micelles then slowly rearrange into clusters of different sizes, which leads to the formation of unilamellar and bilamellar vesicles. The reorganization processes are comparable to those observed by Butler et al. for the marinobactin siderophores produced by marine bacteria, but in contrast to the marinobactins, vesicles of the Fe3+-L(S10) complex form without an excess of iron relative to ligand concentration. The time-dependent micelle-to-vesicle transition is discussed herein.
authors.affiliation: Université Joseph Fourier, Département de Chimie Moléculaire UMR-5250, ICMG FR-2607, CNRS, BP 53, 38041, Grenoble Cedex 9, France.
authors.forename: Lucie
authors.initials: L
authors.lastname: Bednarova
authors.forename: Jérémy
authors.initials: J
authors.lastname: Brandel
authors.forename: Amaury du Moulinet
authors.initials: Adu M
authors.lastname: d'Hardemare
authors.forename: Jan
authors.initials: J
authors.lastname: Bednar
authors.forename: Guy
authors.initials: G
authors.lastname: Serratrice
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Pierre
mesh_terms: D040761:Biomimetic Materials / Q000138:chemical synthesis / Q000737:chemistry; D002396:Catechols / Q000737:chemistry*; D002614:Chelating Agents / Q000138:chemical synthesis* / Q000737:chemistry; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D053520:Marinobacter / Q000737:chemistry*; D015394:Molecular Structure; D010316:Particle Size; D017262:Siderophores / Q000737:chemistry*
chemical_list: D002396:Catechols; D002614:Chelating Agents; D005290:Ferric Compounds; D008024:Ligands; D017262:Siderophores; C034221:catechol