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The observed biological differences in safety and efficacy of intravenous (IV) iron formulations are attributable to physicochemical differences. In addition to differences in carbohydrate shell, polarographic signatures due to ferric iron [Fe(III)] and ferrous iron [Fe(II)] differ among IV iron formulations. Intravenous iron contains Fe(II) and releases labile iron in the circulation. Fe(II) generates...
The aqueous solution equilibria of a β-lactam antimicrobial agent containing a 3-hydroxy, 4-pyridinone group (LPF) binding to Fe(III) in aqueous solution has been characterized through spectrophotometric and potentiometric titrations. The metal-free ligand has four observable protonation constants, pKa1 = 2.6, pKa2 = 3.43, pKa3 = 6.43, and pKa4 = 9.62. LPF forms a 3:1 ligand:Fe(III) complex in aqueous...
The viability of iron(III/II) reduction as the initial step in the in vivo release of iron from its thermodynamically stable siderophore complex is explored.
Hemopexin (HPX) has two principal roles: it sequesters free heme in vivo for the purpose of preventing the toxic effects of this moiety, which is largely due to heme’s ability to catalyze free radical formation, and it transports heme intracellularly thus limiting its availability as an iron source for pathogens. Spectroelectrochemistry was used to determine the redox potential for heme and meso-heme...
Siderophores based on sugar backbones substituted at the 2,3,4- or 2,3,6 positions with hydroxamic or retro-hydroxamic acid chelating units were synthesized and characterized. The alkyl terminus of the iron-coordinating side chain units facilitate lipophilic interactions. Iron coordination properties and complex stability were investigated by ESI-MS and the CAS-Test. The results were correlated to...
While the naturally occurring reducing agents glutathione (GSH) and ascorbate (H2A) alone are ineffective at reducing iron(III) sequestered by the siderophore ferrioxamine B, the addition of an iron(II) chelator, sulfonated bathophenanthroline (BPDS), facilitates reduction by either reducing agent. A mechanism is described in which a ternary complex is formed between ferrioxamine B and BPDS in a rapidly...
Highly toxic beryllium(II) is divalent metal ion with a high charge density, making it a potential target for binding to bio-molecules rich in O donor groups. In aqueous solution Be2+ binds to ATP and ADP to form 1:1 Be2+:ATP and Be2+:ADP complexes in relatively acidic media. At neutral pH the complex formed undergoes hydrolysis. Be2+ binding to ATP and ADP is much stronger than Ca2+ and Mg2+ binding...
In this mini-review we describe selected aspects of the coordination chemistry relevant to siderophore mediated iron transport and bioavailability. Specific emphasis is placed on a discussion of in vitro kinetic and thermodynamic data that are relevant to elucidating possible in vivo mechanisms for environmental iron acquisition by microbial cells.
Treatment of aqueous suspensions of different asbestos fibers (amosite, anthophyllite, chrysotile, and crocidolite) at 0-4°C and pH 7.2 with H O results in the consumption of H O with concomitant release of iron and production of O. During incubations, [H O] decreased in proportion to the mass of the suspended fiber, the duration of incubation, and the initial [H O]. The consumption of H O, production...
Neutrophil influx into tissues occurs in many diverse diseases and can be associated with both beneficial and injurious effects. We hypothesize that the stimulus for certain neutrophilic inflammatory responses can be reduced to a series of competing reactions for iron, with either a labile or reactive coordination site available, between host chelators and chelators not indigenous to that specific...
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