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Siderophore-iron combination

Rhodotorulic acid (RA), a dihydroxamate siderophore, forms dimeric complexes with iron, aluminium and chromium of the stoichiometry M2(RA)3 at neutral pH 36 188). The coordination chemistry of this siderophore is probably the most complicated of the siderophores. The combination of cis-trans, A and A configurations of two iron miters, connected by three RA molecules, makes 42 non-redundant isomers theoretically possible each can be simulated by molecular models. Recently three different isomers or mixtures of isomers of Cr2RA3 were separated by reversed phase HPLC-chromatography177). The visible spectrum of the most abundant fraction corresponds to the cis isomer the two other fractions are very similar to the visible spectrum of the trans Cr(men)3 isomer. The CD spectra, in comparison with the Cr(men)3 model complex, show two different optical isomers, assigned as A -trans and A -trans. The A isomer preparation seems also to contain a certain amount of the A configuration. This is the first time that two different, kinetically stable optical isomers have been isolated from the metal complexes of a siderophore 177). [Pg.90]

Transferrin iron uptake via receptor-mediated endocytosis has clearly appeared fairly late in evolution, when we consider that the bilobal iron-binding protein is found only as far back as insects . As we have seen in the preceding chapters, iron-uptake mechanisms involving the synthesis of more or less specific siderophores have evolved together with strategies implying the solubilization of insoluble ferric iron by the combined effects of pH and reduction, and even the development of receptor proteins capable of taking up transferrin-, lactoferrin- or haem-bound iron from specific hosts. [Pg.164]

Table XVI shows a selection of stability constants and redox potentials for iron(II) and iron(III) complexes. This Table covers a wide range of the latter, showing how the relative stabilities of the iron(II) and iron(III) complexes are refiected in. B (Fe /Fe ) values. A more detailed illustration is provided by the complexes of a series of linear hexadentate hydroxypyridinonate and catecholate ligands, where again high stabilities for the respective iron(III) complexes are refiected in markedly negative redox potentials (213). The combination of the high stabilities of iron(III) complexes of hydrox5rpyridinones, as of hydroxamates, catecholates, and siderophores, and the low stabilities of their iron(II) analogues is also apparent in Fig. 8. Here redox potentials for hydroxypyranonate and hydroxypyridinonate complexes of iron are placed in the overall context of redox potentials for iron(III)/iron(II) couples. The -(Fe /Fe ) range for e.g., water, cyanide, edta, 2,2 -bipyridyl, and (substituted) 1,10-phenanthrolines is... Table XVI shows a selection of stability constants and redox potentials for iron(II) and iron(III) complexes. This Table covers a wide range of the latter, showing how the relative stabilities of the iron(II) and iron(III) complexes are refiected in. B (Fe /Fe ) values. A more detailed illustration is provided by the complexes of a series of linear hexadentate hydroxypyridinonate and catecholate ligands, where again high stabilities for the respective iron(III) complexes are refiected in markedly negative redox potentials (213). The combination of the high stabilities of iron(III) complexes of hydrox5rpyridinones, as of hydroxamates, catecholates, and siderophores, and the low stabilities of their iron(II) analogues is also apparent in Fig. 8. Here redox potentials for hydroxypyranonate and hydroxypyridinonate complexes of iron are placed in the overall context of redox potentials for iron(III)/iron(II) couples. The -(Fe /Fe ) range for e.g., water, cyanide, edta, 2,2 -bipyridyl, and (substituted) 1,10-phenanthrolines is...
Combining fluorescence spectroscopy with fluorescence microscopy, confocal microscopy could be used to elucidate the pathway of siderophore-mediat iron uptake in the fungus Ustilago maydis, and visualize this pathway by providing unique fluorescent microscopic images. Using these techniques, clear images of two independent iron-uptake mechanisms have become visualized as well as their cellular compartment locahzed. [Pg.798]

Experiments performed in vitro revealed that in contrast to DFO, which has a major cytotoxic effect only on trophozoites and early schizonts of P. falciparum, reversed siderophores have a cytotoxic effect on ring-stage and cytostatic effects on trophozoites and schizonts . These observations provided the basis for studying combinations of iron chelators for antimalarial therapy. When DFO is added to malaria parasites cultured in erythrocytes in combination with the more lipophilic and more permeate reversed siderophore 66, a strong synergistic inhibitory effect on parasite growth is observed. This effect may result from the different speeds of permeation of the two chelators... [Pg.806]

The biological rationale for the production of siderophores by microorganisms is the irreplaceable role of iron in nearly all oxidation and reduction processes of cells, combined with the extreme insolubility of ferric hydroxide at physiological pH. At pH 7 the equilibrium concentration for ferric ion (as free [Fe3+]) is approximately... [Pg.51]


See other pages where Siderophore-iron combination is mentioned: [Pg.119]    [Pg.119]    [Pg.224]    [Pg.505]    [Pg.760]    [Pg.77]    [Pg.9]    [Pg.86]    [Pg.140]    [Pg.81]   
See also in sourсe #XX -- [ Pg.102 ]




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