| Mechanism and Kinetics of Ligand Exchange between Ferric Citrate and Desferrioxamine B. | |
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MedLine Citation:
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PMID: 21561126 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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The kinetics of ligand exchange between ferric citrate and desferrioxamine B (DFB) was investigated at pH 8.0 and high citrate/Fe molar ratios (500-5000) with particular attention given to understanding the precise mechanism of ligand exchange. Ferric citrate complexes present in a test solution and therefore involved in the reaction with the incoming ligand (DFB) were initially examined by evaluating ferric citrate speciation on the basis of published thermodynamic constants. The speciation analysis indicated that mononuclear (mono- and dicitrate) ferric complexes are the major species responsible for the ligand exchange with DFB under the conditions examined in the present work. Given the tendency of DFB to adjunctively associate with the ferric citrate complexes, we propose a kinetic model containing the following three mechanisms: (i) direct association of DFB to the ferric dicitrate complex prior to any dissociation of citrate molecules from the Fe center, (ii) adjunctive association of DFB toward ferric monocitrate complex following dissociation of one molecule of citrate from the parent complex, and (iii) complexation of hydrated Fe by DFB after sequential dissociation of two molecules of citrate from the Fe center. Overall rates for the ligand exchange were determined by spectrophotometrically monitoring the formation of ferrioxamine B. Further analysis in quantifying the rate of each mechanism by use of published and determined rate constants of relevant elemental reactions suggested that the first and second mechanisms were significant under our experimental conditions where [Cit] ≫ [DFB] with the relative importance of these two pathways depending on citrate concentration. |
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Authors:
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Hiroaki Ito; Manabu Fujii; Yoshifumi Masago; Chihiro Yoshimura; T David Waite; Tatsuo Omura |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-5-11 |
Journal Detail:
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Title: The journal of physical chemistry. A Volume: - ISSN: 1520-5215 ISO Abbreviation: - Publication Date: 2011 May |
Date Detail:
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Created Date: 2011-5-12 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9890903 Medline TA: J Phys Chem A Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Department of Civil and Environmental Engineering, Tohoku University , Aoba 6-6-06 Aobaku, Sendai 980-8579, Japan. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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