Factors that influence siderophore-mediated iron bioavailability: catalysis of interligand iron(III) transfer from ferrioxamine b to edta by hydroxamic acids

Monzyk, Br̀uce; Crumbliss, Alvin L.

doi:10.1016/0162-0134(83)85010-7

Cited by 28 publications

(10 citation statements)

References 26 publications

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“…2a), which definitively agrees with the slow step observed being the final chelation of the TSC ligands. Summarising, the substitution of DFO by the incoming TSC ligand seems to be governed by the sequential entry, as found for similar systems, 45 and partial coordination (k fast ) followed by the complete tridentate coordination (k slow ) of one of the TSC ligands. After the first initial coordination, DFO dissociates from the ternary Fe III /TSC/DFO complex and fast entry of a second TSC ligand completes the reaction.…”

mentioning

confidence: 99%

Biologically active thiosemicarbazone Fe chelators and their reactions with ferrioxamine B and ferric EDTA; a kinetic study

et al. 2012

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The Fe III abstraction from Fe III /DFO and Fe III /EDTA complex systems by thiosemicarbazone ligands derived from 2-acetylpyridine has been studied from a kinetico-mechanistic perspective at relevant pH conditions and at varying temperatures and buffer solutions. The reactions have been found to be extremely dependent on the dominant E/Z isomeric form of the TSC ligands present in the reaction medium. Consequently the isomerisation processes occurring on the free ligands have also been monitored under equivalent conditions. The isomerisation process is found to be acid dependent, despite the absence of protonation under the conditions used, and presumably proceeds via an azo-type tautomer of the ligand. In all cases the existence of outer-sphere interaction processes has been established, both promoting the reactions and producing dead-end complexes. has also been conducted with significant differences in the kinetic features that implicate keystone outer-sphere interactions which dominate reactivity, even with isomeric forms that are not the best suited for direct complexation.

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confidence: 99%

Biologically active thiosemicarbazone Fe chelators and their reactions with ferrioxamine B and ferric EDTA; a kinetic study

et al. 2012

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“…Siderophores and organic acids are both suitable as iron oxide dissolution agents (Kraemer 2004), which in combination increase the amount of iron available from the environment. The presence of acid anions may also catalyze interligand iron exchange between different siderophores or between siderophores and other chelating compounds involving a ternary complex as a transition state (Monzyk and Crumbliss 1983;Mies et al 2006). Most ferric hydroxamates are stable down to pH 1 without loosing the complexed iron atom and a simultaneous excretion of both, acids and siderophores seems advantageous.…”

Section: Siderophores and Phmentioning

confidence: 98%

Ecology of siderophores with special reference to the fungi

2007

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Ecology of siderophores, as described in the present review, analyzes the factors that allow the production and function of siderophores under various environmental conditions. Microorganisms that excrete siderophores are able to grow in natural low-iron environments by extracting residual iron from insoluble iron hydroxides, protein-bound iron or from other iron chelates. Compared to the predominantly mobile bacteria, the fungi represent mostly immobile microorganisms that rely on local nutrient concentrations. Feeding the immobile is a general strategy of fungi and plants, which depend on the local nutrient resources. This also applies to iron nutrition, which can be improved by excretion of siderophores. Most fungi produce a variety of different siderophores, which cover a wide range of physico-chemical properties in order to overcome adverse local conditions of iron solubility. Resource zones will be temporally and spatially dynamic which eventually results in conidiospore production, transport to new places and outgrow of mycelia from conidiospores. Typically, extracellular and intracellular siderophores exist in fungi which function either in transport or storage of ferric iron. Consequently, extracellular and intracellular reduction of siderophores may occur depending on the fungal strain, although in most fungi transport of the intact siderophore iron complex has been observed. Regulation of siderophore biosynthesis is essential in fungi and allows an economic use of siderophores and metabolic resources. Finally, the chemical stability of fungal siderophores is an important aspect of microbial life in soil and in the rhizosphere. Thus, insolubility of iron in the environment is counteracted by dissolution and chelation through organic acids and siderophores by various fungi.

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“…20 The more water soluble iron(III)-EDTA complex remained dissolved, whereas the methylsulfonamide-DFO derivative precipitated and was collected by filtration. After the pH was adjusted to 8.5 with 5 M KOH, methylsulfonyl chloride (2 mL) dissolved in CHCl 3 (3 mL) was added in a dropwise manner into the stirred ferrioxamine solution over a period of 30 min while maintaining the pH at 8.5.…”

Section: Methylsulfonamide Deferoxaminementioning

confidence: 99%