<![CDATA[The kinetics of iron exchange and iron removal from two siderophore complex with use of ethylenediaminetetraacetic acid (EDTA) have been examined, using UV-Vis spectrophotometric method. Iron exchange between the ferric complexes of desferriferrioxamine B (siderophore produced by microorganism Azomonas macrocy-togenes) with EDTA was extremely slow under conditions at pH 7.4 and 25oC. Furthermore, pH dependence studies demonstrated that the exchange rate was accelerated as a function of increasing hydrogen ion concentration. Kinetics of iron removal from ferrioxamine B and the ferric complexe of azoverdine with excess of EDTA, show firt-order dependence on the concentration of the iron complex and hydrogen ion at 25oC with first-order rate constant of the dissociation of a ternary complex formed of (16 ±0.4) x 10-3s-1 and (1.3 ±0.2) x 10-2s-1 respectivy at pH region between 3.67 and 5.23. variation of pseudo first order rate constant kobs with hydrogen ion concentration shows a saturation kinetics at high constant ligand EDTA concentration (3.0 x 10-2 M) and at low pH region (3.67). the result were interpreted in terms of three-step mechanism, involving : (1) protonation of the ferrioxamine B comples and the ferric comples of azoverdine and (2) subsequent biomolecular reaction with EDTA.]]>
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