A mechanistic study of ferrioxamine B reduction by the biological reducing agent ascorbate in the presence of an iron(II) chelator

Reactions of aqueous iron–DFOB (desferrioxamine B) complexes with flavin mononucleotide in the absence of strong iron(II) chelators

“…To our knowledge, previous studies examining the reduction of Fe III -DFOB by FMN HQ amended reaction solutions with ferrozine or another strong Fe II -complexing colorimetric reagent to monitor Fe II formation during reactions (Halle and Meyer, 1992;Adjimani and Owusu, 1997;Cowart, 2002;Mies et al, 2006;Alderman et al, 2009). However, it has been shown that strong Fe II -chelating ligands can cause a significant positive shift in the reduction potential of the Fe III /Fe II redox couple (Buerge and Hug, 1998;Boukhalfa and Crumbliss, 2002).…”

“…However, in all the above cases, the reaction solutions contain ferrozine or bathophenanthroline disulfonate (BPDS) as colorimetric agents for monitoring formation of Fe II . This presents a fundamental problem because these ligands are strong Fe II -chelating agents that can affect the Fe III /Fe II reduction potential by stabilizing the Fe II reduction product (Mies et al, 2006;Alderman et al, 2009 the Fe III -DFOB complex more amenable to react with physiological reductants. For example, Mies and coworkers report that addition of BPDS to solution is necessary for reduction of Fe III -DFOB complexes by glutathione and ascorbic acid (Mies et al, 2006).…”

Influence of organic ligands on the stoichiometry of magnetite nanoparticles

“…Fe release was larger with EDTA than with citrate because the former is a stronger Fe chelating agent. [63][64][65][66] This can be related to the number of binding groups in the molecule: EDTA may form hexadentate complexes with metal ions as it contains four carboxylic groups and two amines, 37,67,68 while citrate includes three carboxylic groups and one -OH group that might also be involved in the complex formation. 59,69,70 The adsorption of ligands on nanomagnetite was determined and is plotted in Fig.…”

Electrochemical and Solution Structural Characterization of Fe(III) Azotochelin Complexes: Examining the Coordination Behavior of a Tetradentate Siderophore

“…This has led to the speculation of ternary complex formation being a feasible pathway for the modulation of the iron(III) reduction potential in iron(III) siderophore complexes, enabling the reductive iron release mechanism. 12,31,32 Furthermore, there have also been reports on the effects of buffers on the electrochemical behavior of iron(III) siderophores, implying their influence within the second coordination sphere; however, no detailed studies have been reported. 21,26 Azotochelin (Az) is a bis(catecholate) siderophore (Figure 1), one of the three catecholate siderophores secreted by the nitrogen-fixing soil bacterium Azotobacter vinelandii.…”

“…The coordination of alternative ligands at these “vacant” sites can be hypothesized to alter the chemistry of the iron­(III) center, including its reduction potential, particularly if softer donor groups are utilized that stabilize iron­(II) over iron­(III). This has led to the speculation of ternary complex formation being a feasible pathway for the modulation of the iron­(III) reduction potential in iron­(III) siderophore complexes, enabling the reductive iron release mechanism. ,, Furthermore, there have also been reports on the effects of buffers on the electrochemical behavior of iron­(III) siderophores, implying their influence within the second coordination sphere; however, no detailed studies have been reported. , …”