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51.
p-azidobenzoyloxy desferriferricrocin (AF) 2, a photoactivatable analog of ferrichrome, was prepared by selective acylation of the serine group of ferricrocin 1 in two steps: transesterification of ferricrocin followed by demetallation. A model compound, (L) 2-benzyloxycarbonylamino-3-p-azidobenzoyloxy N-isopropyl propionamide 8, was separately synthesized in order to set up optimal transesterification conditions to avoid , -elimination or epimerization of serine. Binding of iron-loaded AF (FeAF) to the FhuA outer membrane receptor protein of Escherichia coli AB2847 was demonstrated by inhibition of ferrichrome transport, interference with the infection by the bacteriophage 80 and with killing of cells by albomycin and colicin M. FeAF transported iron only weakly which indicates that the photoaffinity moiety is incompatible with transport or intracellular iron release from the siderophore. 相似文献
52.
Ute Möllmann Arun Ghosh Eric K. Dolence Julia A. Dolence Manuka Ghosh Marvin J. Miller R. Reissbrodt 《Biometals》1998,11(1):1-12
Conjugates of a carbacephalosporin with hydroxamate, spermexatol, N,N-bis(2,3-dihydroxybenzoyl)-L-lysine, mixed catecholate/hydroxamate and cyanuric acid-based siderophores were investigated for their potential to promote growth of siderophore indicator strains of Gram-negative and Gram-positive bacteria under iron depleted conditions, for their antibacterial activity and for their ability to use iron transport path-ways to penetrate the Gram-negative bacterial outer membrane. The selective growth promotion of enter-obacterial and pseudomonas strains by hydroxamate, spermexatol and mixed catecholate-hydroxamate siderophore-based conjugates bearing a L- or D-amino acid spacer was correlated with TonB dependent uptake routes. The preferred outer membrane siderophore receptor used in Escherichia coli was found to be Fiu, followed by Cir. Antagonistic effects of siderophores administered with the conjugates to determine antibacterial activity confirmed the active transport of conjugates via siderophore receptors. All of the conjugates were still able to diffuse through the porin proteins OmpC and OmpF. Nevertheless, strong inhibition of E. coli and Pseudomones aeruginosa outer membrane mutants DC2 and K799/61 compared to the parent strains indicated inefficient penetrability of all types of conjugates tested. Mycobacterium smegmatis SG 987 was able to use all of the siderophore-cephalosporin conjugates as growth promotors. Consequently there was no growth inhibition of this strain. © Rapid Science 1998. 相似文献
53.
54.
Fluorescent pseudomonads are involved in the natural suppressiveness of some soils to fusarium wilts. These bacteria have been applied successfully to suppress fusarium wilts of various plant species grown in conducive soils and growing substrates. Suppression of fusarium wilts by fluorescent pseudomonads can be ascribed to direct and indirect effects against pathogenic Fusarium oxysporum. Direct effects are expressed by a reduction of the saprophytic growth of the pathogen leading to delay and reduction of root infections. This antagonism was demonstrated to be related to siderophore‐mediated iron competition. Iron competition was also shown to enhance the antagonistic effect of non‐pathogenic F. oxysporum by making the pathogen more susceptible to fungal competition for carbon. Indirect effects of fluorescent pseudomonads against pathogenic F. oxysporum are mainly related to the induction of host plant resistance which can be associated with the bacterial lipopolysaccharides. Suppression of fusarium wilts by some fluorescent pseudomonads could also be related to their ability to detoxify fungal metabolites such as fusaric acid. Association of different mechanisms of suppression increases the efficacy and consistency of the biological control under various experimental conditions. Increased knowledge of mechanisms of suppression now enables management of the environment, to some extent, to favour expression of the beneficial activities. These activities are only expressed if the bacterial density is sufficiently high. 相似文献
55.
Cucumber, as a strategy I plant, and Maize as a strategy II plant, were cultivated in hydroponic culture in the presence of a ferrated siderophore mixture (1 M) from a culture of Penicillium chrysogenumisolated from soil. The siderophore mixture significantly improved the iron status of these plants as measured by chlorophyll concentration to the same degree as a 100-fold higher FeEDTA supply. Analysis of the siderophore mixture from P. chrysogenum by HPLC and electrospray mass spectrometry revealed that besides the trihydroxamates, coprogen and ferricrocin, large amounts of dimerum acid and fusarinines were present which represent precursor siderophores or breakdown products of coprogen. In order to prove the iron donor properties of dimerum acid and fusarinines for plants, purified coprogen was hydrolyzed with ammonia and the hydrolysis products consisting of dimerum acid and fusarinine were used for iron uptake by cucumber and maize. In short term experiments radioactive iron uptake and translocation rates were determined using ferrioxamine B, coprogen and hydrolysis products of coprogen. While the trihydroxamates revealed negligible or intermediate iron uptake rates by both plant species, the fungal siderophore mixture and the ammoniacal hydrolysis products of coprogen showed high iron uptake, suggesting that dimerum acid and fusarinines are very efficient iron sources for plants. Iron reduction assays using cucumber roots or ascorbic acid also showed that iron bound to hydrolysis products of coprogen was more easily reduced compared to iron bound to trihydroxamates. Ligand exchange studies with epi-hydroxymugineic acid and EDTA showed that iron was easily exchanged between coprogen hydrolysis products and phytosiderophores or EDTA. The results indicate that coprogen hydrolysis products are an excellent source for Fe nutrition of plants. 相似文献
56.
Andrew?T.?Koppisch Cindy?C.?Browder Amanda?L.?Moe Jacob?T.?Shelley Blaine?A.?Kinkel Larry?E.?Hersman Srinivas?Iyer Christy?E.?RuggieroEmail author 《Biometals》2005,18(6):577-585
The siderophores of Bacillus anthracis are critical for the pathogen’s proliferation and may be necessary for its virulence. Bacillus anthracis str. Sterne cells were cultured in iron free media and the siderophores produced were isolated and purified using a combination of XAD-2
resin, reverse-phase FPLC, and size exclusion chromatography. A combination of 1H and 13C NMR spectroscopy, UV spectroscopy and ESI-MS/MS fragmentation were used to identify the primary siderophore as petrobactin,
a catecholate species containing unusual 3,4-dihydroxybenzoate moieties, previously only identified in extracts of Marinobacter hydrocarbonoclasticus. A secondary siderophore was observed and structural analysis of this species is consistent with that reported for bacillibactin,
a siderophore observed in many species of bacilli. This is the first structural characterization of a siderophore from B. anthracis, as well as the first characterization of a 3,4-DHB containing catecholate in a pathogen. 相似文献
57.
Staphyloferrin A, the iron-transporting siderophore of Staphylococci, contains two citric acid residues linked to a D-ornithine backbone, having thus three chiral centers. While the chirality of the backbone can be determined after hydrolysis,
the chirality of the two citryl residues can only be determined from the intact staphyloferrin A molecule by circular dichroism
spectra. The chirality of the quarternary carbon atoms of citryl residues in fungal rhizoferrin and bacterial enantio-rhizoferrin have been determined previously to be R,R and S,S respectively. The present investigation shows that of the three
chiral centers in staphyloferrin A, the citryl residues can be assigned an S,S-configuration by comparison with synthetic
analogs, confirming a common chirality among the bacterial enantio-rhizoferrin and staphyloferrin A. This suggests that the bacterial carboxylates originate from a common biosynthetic pathway
leading to an S,S-configuration, while the fungal rhizoferrin possessing an R,R-configuration must have a different biosynthetic
origin. Growth promotion tests with staphylococci revealed that the S,S-configuration of staphyloferrin A and enantio-rhizoferrin enabled iron uptake, while the fungal rhizoferrin with R,R-configuration was not utilized.
Published online December 2004 相似文献
58.
Simon RL Spivak DA 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2004,804(1):203-209
A survey of commercially available amine-based monomers for binding and selectivity of carboxylate and phosphonic acid templates has revealed that the best selectivity is found for the pyridine-based monomers, while the highest affinity was found for 2-(dimethylamino)ethyl methacrylate (2-DEMA, 1). In fact, a more general finding is that selectivity is higher for aromatic amine-based monomers even though affinity remains higher for aliphatic amine-based monomers. An attempt to combine the optimal properties of these two classes of amine monomers, i.e. 2-vinylpyridine (2-VPY, 2), and 2-DEMA by using both simultaneously in a single imprinted polymer resulted in an MIP whose properties were dominated by the aliphatic amine-based monomer 2-DEMA. A controversy between the two commercially available vinylpyridine monomers, 2-VPY and 4-vinylpyridine (4-VPY, 3), was investigated, revealing that neither monomer is generally better for molecular imprinting; rather, the choice of 2-VPY or 4-VPY is template specific (although the preponderance of data tends to frequently favor 4-VPY). Phosphonic acid templates proved to be less successful as templates for molecular imprinting versus carboxylate functionalized templates, although binding was obtained and shown to be controllable via an ion-exchange process. 相似文献
59.
Dennis A EdwardsRobert M Harker Mary F MahonKieran C Molloy 《Inorganica chimica acta》2002,328(1):134-146
Silver carboxylates [Ag(O2CR): R=Me, tBu, 2,4,6-Me3C6H2], fluorocarboxlyates [Ag(O2CRf): Rf=C3F7, C6F13, C7F15] and their phosphine adducts [Ag(O2CR)·nPR3′: R=Me, tBu, 2,4,6-Me3C6H2, R′=Me, Ph, n=2; R=Me, R′=Me, n=3; Ag(O2CRf).2PPh3, Rf=C3F7, C6F13, C7F15] have been synthesised, characterised spectroscopically and used as precursors in the aerosol-assisted chemical vapour deposition of silver films. All the phosphine adducts produced films, though in general PMe3 adducts, proved more successful than PPh3 analogues. The fluoro-carboxylates and their PPh3 adducts all generated silver films, though the growth rate for the adducts was lower. All these latter films showed carbon impurities while fluorine was also evident in most cases. The X-ray structure of AgO2CC3F7·2PPh3 is also reported. 相似文献
60.
Keshia M. Kuhn Carolyn A. Dehner Jennifer L. Dubois Patricia A. Maurice 《Geomicrobiology journal》2013,30(9):780-791
This research investigated the potential role of siderophores in aerobic microbial Fe acquisition from natural organic matter (NOM; XAD-8 isolate and reverse osmosis concentrate pre- and post-Chelex® treatment) through the use of a siderophore-producing Pseudomonas mendocina wild type (WT) bacterium and an engineered mutant (Mt) that was incapable of siderophore production. NOM had complex effects on microbial growth under Fe-limited conditions as measured by optical density, most likely because of the presence of other toxic (trace) metals such as Al, NOM binding interference with additional trace metal nutrients, and/or biofilm development. However, a bioassay for cellular Fe status showed that both WT and Mt readily acquired Fe naturally associated with NOM. Thus, while siderophores may be useful for Fe acquisition from NOM by P. mendocina, they do not appear to be essential for this process. 相似文献