The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Alvin L. Crumbliss - One of the best experts on this subject based on the ideXlab platform.
-
Ternary Complex Formation Facilitates a Redox Mechanism for Iron Release from a Siderophore
Biometals, 2006Co-Authors: Kassy A. Mies, Joseph I. Wirgau, Alvin L. CrumblissAbstract:While the naturally occurring reducing agents glutathione (GSH) and ascorbate (H_2A) alone are ineffective at reducing iron(III) sequestered by the siderophore Ferrioxamine B, the addition of an iron(II) chelator, sulfonated bathophenanthroline (BPDS), facilitates reduction by either reducing agent. A mechanism is described in which a ternary complex is formed between Ferrioxamine B and BPDS in a rapidly established pre-equilibrium step, which is followed by rate limiting reduction of the ternary complex by glutathione or ascorbate. Spectral, thermodynamic, and kinetic evidence are given for ternary complex formation. Ascorbate was found to be slightly more efficient at reducing the ternary complex than glutathione ( k _4=2.1×10^−3 M^−1 s^−1 and k _4=6.3×10^−4 M^−1 s^−1, respectively) at pH 7. Reduction is followed by a rapid ligand exchange step where iron is released from Ferrioxamine B to form tris-(BPDS)iron(II). The implications of these results for siderophore mediated iron transport and release are discussed.
-
Crystal structure of Ferrioxamine B: a comparative analysis and implications for molecular recognition.
Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry, 2001Co-Authors: Suraj Dhungana, Peter S. White, Alvin L. CrumblissAbstract:Ferrioxamine B was successfully co-crystallized with ethanolpentaaquomagnesium(II) and perchlorate ions as counter ions, C27H62Cl3FeMgN6O26, and the crystal structure has been determined by single-crystal X-ray diffraction. The crystals are monoclinic, space group P21/n, four molecules per unit cell with dimensions a=21.1945(7) A, b=10.0034(3) A, c=106.560(1) A, and β=106.560(1)°. The crystal structure contains a racemic mixture of Λ-N-cis,cis and Δ-N-cis,cis coordination isomers. The structural parameters and the conformational features of Ferrioxamine B compare very well with those of Ferrioxamines D1 and E, with an exception of the orientation of the pendant protonated amine, which is pointing away from the connecting amide chains and towards the carbonyl face of the inner coordination shell distorted octahedron. This pendant protonated amine, in conjunction with the carbonyl face of the Fe(III) coordination shell, is proposed to play an important role in the recognition and membrane transport processes.
-
pH Induced Active (“Uphill”) Liquid Membrane Transport of Ferrioxamine B by the Ionizable Ionophore Lasalocid
Inorganic Chemistry, 1999Co-Authors: Ivan Spasojevic, Alvin L. CrumblissAbstract:Active transport of the siderophore Ferrioxamine B by the ionizable ionophore lasalocid, driven by the pH difference in two aqueous phases separated by an artificial membrane, was observed with an average flux of 1.52 × 10-11 mol s-1 cm-2.
-
molecular recognition of Ferrioxamine b by host guest complex formation with lasalocid a in chloroform
Inorganic Chemistry, 1998Co-Authors: Charles D. Caldwell, Alvin L. CrumblissAbstract:The polyether carboxylic acid antibiotic lasalocid A was employed as an ionophore in the extraction of Ferrioxamine B (FeHDFB+) from H2O to CHCl3 at aqueous pH 3 and pH 9. Lasalocid can selectively...
-
Molecular Recognition of Ferrioxamine B by Host−Guest Complex Formation with Lasalocid A in Chloroform
Inorganic Chemistry, 1998Co-Authors: Charles D. Caldwell, Alvin L. CrumblissAbstract:The polyether carboxylic acid antibiotic lasalocid A was employed as an ionophore in the extraction of Ferrioxamine B (FeHDFB+) from H2O to CHCl3 at aqueous pH 3 and pH 9. Lasalocid can selectively...
Klaus Hantke - One of the best experts on this subject based on the ideXlab platform.
-
Molecular recognition of siderophores: A study with cloned Ferrioxamine receptors (FoxA) from Erwinia herbicola and Yersinia enterocolitica
Biometals, 1998Co-Authors: Katja Deiss, Klaus Hantke, Gunther WinkelmannAbstract:The outer membrane receptor for Ferrioxamines (FoxA Erw ) of Erwinia herbicola (Pantoea agglomerans) was cloned from a cosmid gene bank and partially sequenced. A comparison of the partial amino acid sequence of FoxA with the amino acid sequence of FoxA Yer from Yersinia enterocolitica revealed a high sequence homology. A functional analysis of FoxA and FoxA receptors cloned into a Fhu-negative background (HK97) revealed that Ferrioxamines are recognized at very low concentrations (< 10 pmoles) in growth promotion bioassays. A collection of Ferrioxamine derivatives containing varying chain lengths and ether bridges within the molecule was also accepted. However, the three ether containing Ferrioxamine (Et ) behaved differently in the two FoxA receptors. Coprogen was also recognized to a certain extent, whereas ferrichromes were completely excluded from the FoxA receptors, confirming that coprogens share some structural similarities with the Ferrioxamines. FoxA mutants (FM13) of Erwinia herbicola obtained by ferrimycin selection showed no uptake of Fe-labelled Ferrioxamine E and B any more, while the transport of coprogen and ferrichrome was unaffected or even slightly increased. © Rapid Science 1998
-
iron hydroxamate uptake systems in bacillus subtilis identification of a lipoprotein as part of a binding protein dependent transport system
Molecular Microbiology, 1993Co-Authors: Richard Schneider, Klaus HantkeAbstract:Bacillus subtilis was shown to utilize three types of hydroxamate siderophores, ferrichromes, Ferrioxamines and shizokinen, each of which is taken up by different transport systems. Mutants deficient in the uptake of ferrichrome and/or Ferrioxamine B were isolated. The gene fhuD, which was able to complement a mutant defective in ferrichrome uptake, was cloned. The deduced sequence of FhuD showed low but significant homology to the binding proteins FepB, FecB and FhuD of Escherichia coli, which are all components of binding protein-dependent, ferric siderophore transport systems. The first 23 amino acids of FhuD of B. subtilis possessed all characteristics of a lipoprotein signal sequence. The processing of FhuD in E. coli was inhibited by globomycin. Inhibition by globomycin indicated a lipid modification at the N-terminal cysteine in E. coli. It is highly likely that this step may also take place in B. subtilis. As in other binding protein-dependent transport systems of Gram-positive organisms it is proposed that the lack of a periplasm is compensated for by the lipid through which the binding protein is anchored to the cytoplasmic membrane.
-
A lipoprotein of Yersinia enterocolitica facilitates Ferrioxamine uptake in Escherichia coli.
Journal of bacteriology, 1992Co-Authors: Andreas J. Bäumler, Klaus HantkeAbstract:A cloned fragment of Yersinia enterocolitica DNA complemented the defect in Ferrioxamine B uptake of an Escherichia coli fhuE mutant lacking the outer membrane high-affinity transport protein FhuE. Subcloning revealed that a 13.7-kDa outer membrane protein was required for complementation. The amino acid sequence deduced from the nucleotide sequence showed extensive homology to PCPHi, an outer membrane lipoprotein of Haemophilus influenzae. We therefore termed this protein PCPYe. Plasmid-encoded pcpY mediated a low-affinity uptake of Ferrioxamine B which may be caused by changes in the permeability of the outer membrane due to an overexpression of this outer membrane protein. A transposon insertion mutant in the plasmid-encoded pcpY gene was transferred into the chromosome of Y. enterocolitica. The resulting mutation had no effect on the high-affinity uptake of Ferrioxamine B in Yersinia cells. Using the antibiotic ferrimycin we were able to isolate a Y. enterocolitica mutant lacking the high-affinity outer membrane receptor for Ferrioxamine uptake, termed FoxA.
Ivan Spasojevic - One of the best experts on this subject based on the ideXlab platform.
-
pH Induced Active (“Uphill”) Liquid Membrane Transport of Ferrioxamine B by the Ionizable Ionophore Lasalocid
Inorganic Chemistry, 1999Co-Authors: Ivan Spasojevic, Alvin L. CrumblissAbstract:Active transport of the siderophore Ferrioxamine B by the ionizable ionophore lasalocid, driven by the pH difference in two aqueous phases separated by an artificial membrane, was observed with an average flux of 1.52 × 10-11 mol s-1 cm-2.
-
Lariat Ether Carboxylic Acids as Ionizable Hosts in the Second Coordination Sphere of the Siderophore Ferrioxamine B in Chloroform
Inorganic Chemistry, 1998Co-Authors: Ines Batinic-haberle, Ivan Spasojevic, Y. Jang, Richard A. Bartsch, Alvin L. CrumblissAbstract:A new series of lariat ether carboxylic acids (LnCOOH) was synthesized with different lengths of side arm (6, 9, and 12 atom spacers between the benzo-18-crown-6 crown ether ring and the carboxylic acid functional group). These lariat ethers were used as neutral and anionic hosts for the molecular recognition of the cationic siderophore, Ferrioxamine B. Lariat ether pKa values were determined by potentiometric titration in 50% methanol (v/v) to be in the range 5.23−5.32. Molecular recognition of Ferrioxamine B occurs through second-sphere complexation of the pendant protonated amine (−(CH2)5NH3+) by the lariat ether cavity, utilizing an ion−dipole host−guest interaction to form a supramolecular assembly in wet chloroform. At conditions where the pendant carboxylic acid side arm is not ionized (pH = 3.2), the lariat ethers behave as the parent unsubstituted crown ether structure, benzo-18-crown-6 (B18C6). At pH conditions well above their pKa values, the lariat ether carboxylic acids function both as a hos...
-
BULK LIQUID MEMBRANE TRANSPORT OF Ferrioxamine B BY NEUTRAL AND IONIZABLE CARRIERS
Journal of the Chemical Society Dalton Transactions, 1998Co-Authors: Ivan Spasojevic, Alvin L. CrumblissAbstract:Bulk liquid membrane (BLM) transport of Ferrioxamine B (FeHDFB+) across an artificial hydrophobic membrane facilitated by neutral and ionizable carriers was studied. Under controlled conditions, Ferrioxamine B transport by neutral ionophores follows a simple theoretical model for a diffusion controlled process which predicts a linear dependence of flux upon aqueous-to-chloroform extraction constants. Unsubstituted 18C6 crown ether exhibits the best transport properties among the neutral carriers investigated with a flux of 1.4 × 10–10 mol s–1 cm–2. When transport of FeHDFB+, metal-free desFerrioxamine B, H4DFB+, and AlHDFB+ mediated by DC18C6 crown ether was followed, a selectivity was observed with a ratio of measured relative fluxes of 5∶3∶1, respectively. An ionizable carrier lasalocid {6-[7-[5-ethyl-5-(5-ethyltetrahydro-5-hydroxy-6-methyl-2H-pyran-2-yl)tetrahydro-3-methyl-2-furanyl]-4-hydroxy-3,5-dimethyl-6-oxonoyl]-2-hydroxy-3-methylbenzoic acid}, negatively charged at neutral pH, outperformed the crown ethers as a Ferrioxamine B transporting agent. However, transport by ionizable carriers follows a different mechanism and occurs only when an electrolyte is present in the receiving phase. This requirement was exploited by designing a BLM experiment in which H4DFB+ acts as a counter cation at the receiving interface, whereby FeHDFB+ and H4DFB+ were transported in opposite directions in a synergistic fashion. When the ionizable salicylic acid moiety of lasalocid is transformed into an ester, lasalocid almost entirely loses its transporting properties. This suggests a co-operative mode of binding in which electrostatic recognition of the FeHDFB+ cation by lasalocid anion is a prerequisite for a subsequent encapsulation of the amine site in a host–guest fashion.
-
second sphere coordination of Ferrioxamine b and association of deferriFerrioxamine b ch 3 ch 2 4 nh 3 nh 4 k and mg 2 with synthetic crown ethers and the natural ionophores valinomycin and nonactin in chloroform
Inorganic Chemistry, 1996Co-Authors: Ines Batinichaberle, Ivan Spasojevic, Alvin L. CrumblissAbstract:The interaction of Ferrioxamine B, FeHDFB(+), through a protonated amine side chain, with various host ionophore structures to form a host-guest complex in the second coordination shell has been investigated. Host-guest association constants (K(a)) in water saturated chloroform are reported for synthetic crown ethers with different cavity size and substituents (18-crown-6 and its dicyclohexano, benzo, and dibenzo derivatives; dibenzo and dicyclohexano derivatives of 24-crown-8; and dibenzo-30-crown-10). The natural ionophores valinomycin and nonactin were also found to form stable second-sphere complexes with Ferrioxamine B in wet chloroform. Results are reported for both picrate and perchlorate salts of FeHDFB(+). Since the protonated amine side chain of Ferrioxamine B may be viewed as a substituted amine, the host-guest association constants for FeHDFB(+) are compared to the interaction of Mg(2+), K(+), NH(4)(+), CH(3)(CH(2))(4)NH(3)(+), and H(4)DFB(+) with the same ionophores. This is the first report of nonactin complexation of this series of cations in an organic medium of low polarity and one of the few reports of valinomycin complexation. To the best of our knowledge these are the first reported stability constants for the association of (Mg(2+),2pic(-)) with natural and synthetic ionophores in chloroform. K(a) values for Ferrioxamine B complexation by the synthetic crown ethers are influenced by ring size and substituent. Despite significant preorganization capabilities, the large cavities of valinomycin, nonactin and benzo-30-crown-10 do not form as stable host-guest assemblies with bulky substituted amine cations such as Ferrioxamine B as does cis-dicyclohexano-18-crown-6.
-
Second-Sphere Coordination of Ferrioxamine B and Association of DeferriFerrioxamine B, CH(3)(CH(2))(4)NH(3)(+), NH(4)(+), K(+), and Mg(2+) with Synthetic Crown Ethers and the Natural Ionophores Valinomycin and Nonactin in Chloroform.
Inorganic chemistry, 1996Co-Authors: Ines Batinic-haberle, Ivan Spasojevic, Alvin L. CrumblissAbstract:The interaction of Ferrioxamine B, FeHDFB(+), through a protonated amine side chain, with various host ionophore structures to form a host-guest complex in the second coordination shell has been investigated. Host-guest association constants (K(a)) in water saturated chloroform are reported for synthetic crown ethers with different cavity size and substituents (18-crown-6 and its dicyclohexano, benzo, and dibenzo derivatives; dibenzo and dicyclohexano derivatives of 24-crown-8; and dibenzo-30-crown-10). The natural ionophores valinomycin and nonactin were also found to form stable second-sphere complexes with Ferrioxamine B in wet chloroform. Results are reported for both picrate and perchlorate salts of FeHDFB(+). Since the protonated amine side chain of Ferrioxamine B may be viewed as a substituted amine, the host-guest association constants for FeHDFB(+) are compared to the interaction of Mg(2+), K(+), NH(4)(+), CH(3)(CH(2))(4)NH(3)(+), and H(4)DFB(+) with the same ionophores. This is the first report of nonactin complexation of this series of cations in an organic medium of low polarity and one of the few reports of valinomycin complexation. To the best of our knowledge these are the first reported stability constants for the association of (Mg(2+),2pic(-)) with natural and synthetic ionophores in chloroform. K(a) values for Ferrioxamine B complexation by the synthetic crown ethers are influenced by ring size and substituent. Despite significant preorganization capabilities, the large cavities of valinomycin, nonactin and benzo-30-crown-10 do not form as stable host-guest assemblies with bulky substituted amine cations such as Ferrioxamine B as does cis-dicyclohexano-18-crown-6.
Ines Batinic-haberle - One of the best experts on this subject based on the ideXlab platform.
-
Lariat Ether Carboxylic Acids as Ionizable Hosts in the Second Coordination Sphere of the Siderophore Ferrioxamine B in Chloroform
Inorganic Chemistry, 1998Co-Authors: Ines Batinic-haberle, Ivan Spasojevic, Y. Jang, Richard A. Bartsch, Alvin L. CrumblissAbstract:A new series of lariat ether carboxylic acids (LnCOOH) was synthesized with different lengths of side arm (6, 9, and 12 atom spacers between the benzo-18-crown-6 crown ether ring and the carboxylic acid functional group). These lariat ethers were used as neutral and anionic hosts for the molecular recognition of the cationic siderophore, Ferrioxamine B. Lariat ether pKa values were determined by potentiometric titration in 50% methanol (v/v) to be in the range 5.23−5.32. Molecular recognition of Ferrioxamine B occurs through second-sphere complexation of the pendant protonated amine (−(CH2)5NH3+) by the lariat ether cavity, utilizing an ion−dipole host−guest interaction to form a supramolecular assembly in wet chloroform. At conditions where the pendant carboxylic acid side arm is not ionized (pH = 3.2), the lariat ethers behave as the parent unsubstituted crown ether structure, benzo-18-crown-6 (B18C6). At pH conditions well above their pKa values, the lariat ether carboxylic acids function both as a hos...
-
Second-Sphere Coordination of Ferrioxamine B and Association of DeferriFerrioxamine B, CH(3)(CH(2))(4)NH(3)(+), NH(4)(+), K(+), and Mg(2+) with Synthetic Crown Ethers and the Natural Ionophores Valinomycin and Nonactin in Chloroform.
Inorganic chemistry, 1996Co-Authors: Ines Batinic-haberle, Ivan Spasojevic, Alvin L. CrumblissAbstract:The interaction of Ferrioxamine B, FeHDFB(+), through a protonated amine side chain, with various host ionophore structures to form a host-guest complex in the second coordination shell has been investigated. Host-guest association constants (K(a)) in water saturated chloroform are reported for synthetic crown ethers with different cavity size and substituents (18-crown-6 and its dicyclohexano, benzo, and dibenzo derivatives; dibenzo and dicyclohexano derivatives of 24-crown-8; and dibenzo-30-crown-10). The natural ionophores valinomycin and nonactin were also found to form stable second-sphere complexes with Ferrioxamine B in wet chloroform. Results are reported for both picrate and perchlorate salts of FeHDFB(+). Since the protonated amine side chain of Ferrioxamine B may be viewed as a substituted amine, the host-guest association constants for FeHDFB(+) are compared to the interaction of Mg(2+), K(+), NH(4)(+), CH(3)(CH(2))(4)NH(3)(+), and H(4)DFB(+) with the same ionophores. This is the first report of nonactin complexation of this series of cations in an organic medium of low polarity and one of the few reports of valinomycin complexation. To the best of our knowledge these are the first reported stability constants for the association of (Mg(2+),2pic(-)) with natural and synthetic ionophores in chloroform. K(a) values for Ferrioxamine B complexation by the synthetic crown ethers are influenced by ring size and substituent. Despite significant preorganization capabilities, the large cavities of valinomycin, nonactin and benzo-30-crown-10 do not form as stable host-guest assemblies with bulky substituted amine cations such as Ferrioxamine B as does cis-dicyclohexano-18-crown-6.
-
Hydrolysis of Ferrioxamine B in Aqueous Micellar Solution
Inorganic Chemistry, 1994Co-Authors: Ines Batinic-haberle, Ivan Spasojevic, Alvin L. CrumblissAbstract:The association constant for the Fe(III) complex of the linear trihydroxamic acid siderophore Ferrioxamine B (FeHDFB + ;HDFB 2 =H 3 N-[(CH 2 ) 5 -N(O)C(O)-(CH 2 ) 2 C(O)NH-] 2 (CH 2 ) 5 -N(O)C(O)-CH 3 binding sulfate (SDS) micelles was deterined by ultrafiltration and kinetics methods. Both methods are in agreement and yield an average value of the association constant K m =98 M -1 . Association constants for the Al(III) analogue of Ferrioxamine B, AlHDFB + , and the metal-free ligand deferriFerrioxamine B, H 4 DFB + , were also determined by ultrafiltration and found to be K m =90 and 362 M -1 , respectively
Yeala Shaked - One of the best experts on this subject based on the ideXlab platform.
-
Metallophores associated with Trichodesmium erythraeum colonies from the Gulf of Aqaba
Metallomics, 2019Co-Authors: Martha Gledhill, Subhajit Basu, Yeala ShakedAbstract:Trichodesmium is a globally important marine nitrogen fixing cyanobacteria which forms colonies and utilizes atmospherically derived dust as a source for the limiting micro-nutrient iron. Here we report the identification of metallophores isolated from incubations of natural Trichodesmium colonies collected from the Gulf of Aqaba in the Red Sea. Three of our compounds were identified as the Ferrioxamine siderophores B, E, and G. The remaining fifteen metallophores had mass to charge ratios that, to our knowledge, are not common to known siderophores. Putative sum formulas suggest most of these compounds were not structurally related to each other. We also found that the novel metallophores readily formed complexes with aluminium and were less specific for iron than the Ferrioxamines. In our incubations of Trichodesmium colonies, the abundance of ten of the novel metallophores positively correlated with Trichodesmium biomass, but not with bacterial biomass, whilst Ferrioxamine siderophores were more strongly associated with bacterial biomass. We identified Ferrioxamines and our novel metallophores in filtered surface seawater samples from the Gulf of Aqaba. However, our novel metallophores were only observed in the surface seawater sample collected at the time of highest Trichodesmium abundance, while Ferrioxamines were observed even when Trichodesmium was not present. We hypothesize that the novel metallophores were specifically associated with Trichodesmium colonies. Together with the bacterially produced Ferrioxamines they likely contribute to a distinctive "ligandosphere" surrounding the Trichodesmium colonies, with potential implications for metal homeostasis within the colony environment.