Trafficking of Siderophore Transporters in Saccharomyces cerevisiae and Intracellular Fate of Ferrioxamine B Conjugates

We have studied the intracellular trafficking of Sit1 [ferrioxamine B (FOB) transporter] and Enb1 (enterobactin transporter) in Saccharomyces cerevisiae using green fluorescent protein (GFP) fusion proteins. Enb1 was constitutively targeted to the plasma membrane. Sit1 was essentially targeted to the vacuolar degradation pathway when synthesized in the absence of substrate. Massive plasma membrane sorting of Sit1 was induced by various siderophore substrates of Sit1, and by coprogen, which is not a substrate of Sit1. Thus, different siderophore transporters use different regulated trafficking processes. We also studied the fate of Sit1-mediated internalized siderophores. Ferrioxamine B was recovered in isolated vacuolar fractions, where it could be detected spectrophotometrically. Ferrioxamine B coupled to an inhibitor of mitochondrial protoporphyrinogen oxidase (acifluorfen) could not reach its target unless the cells were disrupted, confirming the tight compartmentalization of siderophores within cells. Ferrioxamine B coupled to a fluorescent moiety, FOB-nitrobenz-2-oxa-1,3-diazole, used as a Sit1-dependent iron source, accumulated in the vacuolar lumen even in mutants displaying a steady-state accumulation of Sit1 at the plasma membrane or in endosomal compartments. Thus, the fates of siderophore transporters and siderophores diverge early in the trafficking process

A new route to trihydroxamate-containing artificial siderophores and synthesis of a new fluorescent probe.

A fluorescent labelled artificial siderophore 1 was synthesized by coupling a 7-nitrobenz-2-oxa-1,3-diazole (NBD) derivative to the terminal amino group of a new trihydroxamate-containing amine 2, a ferrichrome-type siderophore that was obtained from tris(hydroxymethyl) amino methane. Compound I was shown to be a suitable tool for experiments on siderophore transport and uptake processes in various organisms cells and particularly in Candida albicans cells

A facile route to steady redox-modulated nitroxide spin-labeled surfaces based on diazonium chemistry.

International audienceA TEMPO derivative was covalently grafted onto carbon and gold surfaces via the diazonium chemistry. The acid-dependent redox properties of the nitroxyl group were exploited to elaborate electro-switchable magnetic surfaces. ESR characterization demonstrated the reversible and permanent magnetic character of the material

Nitroxyl radical self assembled monolayers: Ion pairing investigation in organic and aqueous media

Self assembled monolayers (SAMs) formed from TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) derivative thiols have been studied by electrochemical quartz crystal microbalance (EQCM) in both aqueous and non-aqueous solvents. The in situ study of the mass transport occurring during the oxidation of TEMPO provides evidence of a ion pair formation without incorporation of solvent in densely packed nitroxyl radical SAMs. For SAMs having a low nitroxyl radical surface coverage, the effect of mixed SAMs is evidenced and seems to avoid the solvent incorporation. Keywords: Tempo, Self assembled monolayers, Cyclic voltammetry, Ion pairin

Electroactive self-assembled monolayers: Laviron's interaction model extended to non-random distribution of redox centers

The Laviron's interaction model, dedicated to randomly distributed electroactive adsorbed species, was extended to a non-random distribution in order to extract the current–voltage characteristics from any surface distribution of electroactive centers on self-assembled monolayer (SAM). Confronted to electrochemical behaviour of nitroxyl radical SAMs, the agreement observed between theory and experiments provides evidence of a distribution independence of the interaction parameters. Keywords: Tempo, Self-assembled monolayers, Cyclic voltammetry, Interaction mode

Revisiting the determination of full steady-state coverage of redox centers on self-assembled monolayers

This work establishes an experimental estimation of the full steady-state coverage of redox centers on self-assembled monolayers. The results demonstrate that the assessment of the full surface coverage and the adsorption kinetic from a Langmuir model impose drastic experimental conditions. Keywords: Full steady-state coverage, Self-assembled monolayers, Cyclic voltammetry, Langmuir isother

Design, synthesis and redox properties of two ferrocene-containing iron chelators.

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Self-assembled monolayer-assisted mass spectrometry

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