XAS study of a metal-induced phase transition by a microbial surfactant.

TitleXAS study of a metal-induced phase transition by a microbial surfactant.
Publication TypeJournal Article
Year of Publication2008
AuthorsOwen T, Webb SM, Butler A
JournalLangmuir
Volume24
Issue9
Pagination4999-5002
Date Published2008 May 6
ISSN0743-7463
KeywordsAbsorption, Cadmium, Iron, Molecular Structure, Oligopeptides, Palmitic Acids, Phase Transition, Spectrum Analysis, Surface-Active Agents, X-Ray Diffraction, Zinc
Abstract

The metal-induced micelle-to-vesicle phase change that the ferric complex of the microbially produced amphiphile, marinobactin E (M(E)), undergoes has been investigated by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Marinobactin E is one member of the suite of siderophores, marinobactins A-E, that are used by the source bacterium to facilitate iron acquisition. Fe(III)-M(E) undergoes a micelle-to-multilamellar vesicle transition in the presence of Cd(II) and Zn(II). XRD measurements indicate the interlamellar repeat distance of the Cd(II)- and Zn(II)-induced multilamellar vesicles is approximately 5.3 nm. XAS spectra of the sedimented Cd(II)- and Zn(II)-induced multilamellar vesicles suggests hexadentate coordination of Cd(II) and Zn(II) consisting of two monodentate carboxylate ligands and four water ligands. This coordination environment supports the hypothesis that Cd(II) and Zn(II) bridge the terminal carboxylate moiety of two Fe(III)-M(E) headgroups, pulling the headgroups together in an arrangement that favors vesicle formation over the formation of micelles. XAS spectra of the Fe(III) center in the sedimented Cd(II)- and Zn(II)-induced vesicles confirm the anticipated six-coordinate geometry of Fe(III) by the M(E) headgroup via the two hydroxamate groups and the alpha-hydroxy amide moiety.

DOI10.1021/la703833v
Alternate JournalLangmuir
PubMed ID18442226
PubMed Central IDPMC3068532
Grant ListGM38130 / GM / NIGMS NIH HHS / United States
R01 GM038130-15 / GM / NIGMS NIH HHS / United States
R01 GM038130-16 / GM / NIGMS NIH HHS / United States