Solution thermodynamics of the ferric complexes of new desferrioxamine siderophores obtained by directed fermentation

The determination of ferric iron in plants by HPLC using the microbial iron chelator desferrioxamine E

“…Therefore, the use of DFE for iron determination in organic fluids proves advantageous as compared with DFB, since no interaction with compounds present in samples can be expected. DFE can extract iron from a variety of soluble iron complexes and the formed FoxE complex is stable down to pH 1 with only slight changes of absorption maximum and extinction coefficient ( -Rapp et al 1992). Iron bound to citrate and other carboxylate ligands and even insoluble ferric phosphates and ferritin can be solubilized and complexed in the presence of DFE.…”

Solution equilibria of deferoxamine amides

“…Titration data were presented to the algorithm using a mathematical model for the ionization equilibria of a triprotic or quatroprotic acid 14,15. Initial estimates of the hydroxamate pKa values, required to run the program, were obtained from a report concerning the iron complexing behaviour of novel siderophores 7,11. The trihydroxamic acid analog titration curves were fit to a three parameter model while the succinamide derivative titrations were interpreted using a four‐parameter model previously used for DFO 14…”

“…The stability constant (β) was restated in terms of the proton‐dependent ferric ion coordination reaction coupled to the pH‐dependent competition between the DFO analog and EDTA for ferric ion. The exchange of ferric ion between DFO analog and EDTA was monitored spectrophotometrically 10,11. The experiments were conducted in the pH range of 4 to 6.5 in which the DFO amides would be stable to hydrolysis and ferric hydroxide formation is minimal 12,13.…”

Microbial Siderophores

“…By feeding of suitable diamino precursors to the culture medium unnatural analogs can be obtained (111,194,227). At pH values above 6.5 (Fe 3+ ) 2 Lig 3 complexes prevail, in more acidic media Fe 3+ Lig is formed (194). The crystals of the Fe 3+ Lig complexes of ferrioxamine D 1 and E are racemic mixtures of L-cis and D-cis coordination isomers (154, 366a).…”

“…The terminal acid residue can also be missing (referred to as "truncated") (115,398). By feeding of suitable diamino precursors to the culture medium unnatural analogs can be obtained (111,194,227). At pH values above 6.5 (Fe 3+ ) 2 Lig 3 complexes prevail, in more acidic media Fe 3+ Lig is formed (194).…”