title: Mn(II)/Mn(III) and Fe(III) binding capability of two Aspergillus fumigatus siderophores, desferricrocin and N', N″, N‴-triacetylfusarinine C.
abstract: Manganese(II) and manganese(III) complexes of the exocyclic desferricrocin (H3DFCR) and endocyclic triacetylfusarinine C (H3TAF) in solution have been studied by using pH-potentiometry, UV-Vis spectrophotometry, relaxometry and cyclic voltammetry. A comparison between the present results and the corresponding ones for the open-chain analogues, desferrioxamine B (DFB) and desferricoprogen (DFC), shows (i) The dissociation processes of H3DFCR occur in the expected pH-range (pH7-10.5), but hydrogen bonding is assumed to be responsible for a quite low proton dissociation constant (pK=4.18) of H3TAF and also an unusually high one (10.59). (ii) Moderate stability complexes with 1:1 Mn(II) to ligand ratio are formed with all four siderophores. (iii) The coordination of the three hydroxamates of a siderophore takes place in stepwise processes, except the case of desferricrocin, with which, large-extent overlapping of the processes occurs. (iv) Out of the four tris-chelated [ML] type complexes, the complex of DFCR is the most compact, as it is indicated by the relaxivity values. (v) Following the stoichiometric oxidation of the Mn(II)-siderophore complexes at pH≥9, tris-chelated Mn(III) complexes are formed. To make a comparison between the stability of the Mn(III) and the corresponding Fe(III) complexes of DFCR and TAF, the determination of the stability of the Fe(III) complexes under our condition has also been performed, by using UV-Vis spectrophotometry. Comparable stability of the corresponding complexes was found. (vi) Correlation study of the stability constants resulted in estimation of the constant of the Mn(III) monohydroxo complex, for which there was no data in the literature under our conditions.
authors: Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4010 Debrecen, POB 21, Hungary. Electronic address: efarkas@science.unideb.hu.
authors: Etelka
authors: E
authors: Farkas
authors: MTA-DE Homogenous Catalysis and Reaction Mechanisms Research Group, Debrecen, Hungary.
authors: Orsolya
authors: O
authors: Szabó
authors: Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4010 Debrecen, POB 21, Hungary.
authors: Péter L
authors: PL
authors: Parajdi-Losonczi
authors: Vascular Biology, Thrombosis and Hemostasis Research Group, Hungarian Academy of Sciences, Debrecen, Hungary; Department of Neonatology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary.
authors: György
authors: G
authors: Balla
authors: Department of Microbiology and Biotechnology, University of Debrecen, H-4010 Debrecen, POB 63, Hungary.
authors: István
authors: I
authors: Pócsi
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D001232:Aspergillus fumigatus; D056831:Coordination Complexes / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006877:Hydroxamic Acids / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D011485:Protein Binding; D055550:Protein Stability; D017262:Siderophores / Q000737:chemistry*
chemical_list: D023181:Antimicrobial Cationic Peptides; D056831:Coordination Complexes; D005290:Ferric Compounds; D005656:Fungal Proteins; D006877:Hydroxamic Acids; D017262:Siderophores; C015790:desferri-ferricrocin; D008345:Manganese; C053324:N,N',N''-triacetylfusarinine C; D007501:Iron
keywords: Hydroxamate based siderophores; Manganese(II)/(III) and iron(III) complexes; Manganese(III)-monohydroxo complex; Redox behaviour; Relaxivity; Solution equilibria