Ferric hydroxamate

ABC transporters involved in the uptake of siderophores, haem, and vitamin B]2 are widely conserved in bacteria and Archaea (see Figure 10). Very few species lack representatives of the siderophore family transporters. These species are mainly intracellular parasites whose metabolism is closely coupled to the metabolism of their hosts (e.g. mycoplasma), or bacteria with no need for iron (e.g. lactobacilli). In many cases, several systems of this transporter family can be detected in a single species, thus allowing the use of structurally different chelators. Most systems were exclusively identified by sequence data analysis, some were biochemically characterised, and their substrate specificity was determined. However, only very few systems have been studied in detail. At present, the best-characterised ABC transporters of this type are the fhuBCD and the btuCDF systems of E. coli, which might serve as model systems of the siderophore family. Therefore, in the following sections, this report will mainly focus on the components that mediate ferric hydroxamate uptake (fhu) and vitamin B12 uptake (htu). 

As mentioned above, transport of siderophores across the cytoplasmic membrane is less specific than the translocation through the outer membrane. In E. coli three different outer membrane proteins (among them FepA the receptor for enterobactin produced by most E. coli strains) recognise siderophores of the catechol type (enterobactin and structurally related compounds), while only one ABC system is needed for the passage into the cytosol. Likewise, OM receptors FhuA, FhuE, and Iut are needed to transport a number of different ferric hydroxamates, whereas the FhuBCD proteins accept a variety of hydroxamate type ligands such as albomycin, ferrichrome, coprogen, aerobactin, shizokinen, rhodotorulic acid, and ferrioxamine B [165,171], For the vast majority of systems, the substrate specificity has not been elucidated, but it can be assumed that many siderophore ABC permeases might be able to transport several different but structurally related substrates. 

An official gas chromatographic method [29] is available from the determination of volatile fatty acids in sewage sludge. This method is based on gas liquid chromatographic estimation with a flame ionization detector, and is applicable up to 2000mg total volatile fatty acids per litre, while the concentrations of individual fatty acids can also be determined. Where this method is not practicable an empirical method based on the spectrophotometric determination of ferric hydroxamates can be used, giving a value for total fatty acids expressed as acetic acid. For control purposes a rapid test is described in which the volatile fatty acids are determined by electrometric titrimetry on the neutralized sludge obtained from the determination of alkalinity. 

Mixed donor ligands. Tris(acetylhydrazine)iron(iii) trichloride has been pre-pared. ° The effect of pressure on ferric hydroxamates is to cause reduction to iron(ii), the amount of reduction being correlated with the position of the metal-> ligand charge-transfer band. Fe " complexes of A-hydroxyurea have been isolated. 8-Amino-7-hydroxy-4-methylcoumarin (58) forms the complex [FegLjCl ], in which the Fe " ions are in octahedral environments. A magnetic and Mossbauer study of [FeX(ox)2] and [FeX2(ox)] (X = Cl or... 

Nitriles Ferric hydroxamate-propylene glycol Red color 40... 

A remarkable property of the hydroxamates is the pronounced specificity for ferric iron and even very simple model compounds like acethy-droxamic acid have stability constants approaching 1030 (Table 1). Ferrous iron is bound only relatively weakly and this discrepancy in the avidity for the two oxidation states is powerful evidence that the ferric hydroxamates do not function biologically, as do the hemes, by alternate oxidation and reduction. On the other hand these properties provide a simple means of pick up, transfer and release of iron at the point of demand in living cells. 

Hassib et al. [29] determined mefenamic acid by ferric hydroxamate complex formation and measurement of the absorbance of the colored complex at 530 nm. The method is applicable to mefenamic acid amounts varying from 0.5 to 74.5 mg/25 mL, and Ponstan capsules were successfully determined using this method. 

Cephalothin can be determined by means of the colored complex formed on the addition of a ferric reagent to the corresponding hy-droxamic acid produced by treatment with hy-droxylamine. The method used is essentially the same.as the procedure described for penicillins. The ferric hydroxamate procedure is not specific for cephalothin or penicillins. For example, many amides, esters, and anhydrides form hydroxamic acids when reacted with hydroxyl-amine. This type of interference is eliminated by the blank determination wherein cephalothin is rendered incapable of forming hydroxamic acid by use of basic hydrolysis or enzymatic hydrolysis with cephalosporinase. Since cephalothin degradation products having an intact (3-lactam ring react as well as the parent compound, the method measures total 3-lactam content. ... 

Figure 19 shows the time-dependent 55Fe exchange between two ferric hydroxamate siderophore complexes ferrioxamine B and ferrichrome A.165) This process is an extremely slow pseudo-first order reaction under the conditions described, which is only 50% completed after 220 hours of incubation at 25 °C and pH 7.4. Lowering... 

A sensitive and reproducible colorimetric determination of the tropane alkaloids by the ferric hydroxamate method has been described,18 and so has the nitration and dehydration of tropane alkaloids on the microgram scale on tie. plates.19... 

In vitro release tests were carried out on 200 mg samples of polymer films, by determining pilocarpine release to a stirred aqueous medium (pH 6.98 phosphate buffer, 10.0 ml) at 30 °C. Solution samples (2.0 ml) were withdrawn at appropriate intervals, and were replaced with an equal amount of fresh buffer. Pilocarpine was analyzed spectrophotometrically by the ferric hydroxamate method described by Gibbs and Tuckerman... 

I. S. Gibbs and M. M. Tuckerman, Optimal Ferric Hydroxamate Method for Determination of Intact Pilocarpine, J. Pharm. Sci. 59 395 (1970). 

Although esters, like aldehydes and ketones, are neutral compounds that have a carbonyl group, they do not usually give a positive 2,4-dinitrophenylhydrazine test result. The two most common tests for identifying esters are the basic hydrolysis and ferric hydroxamate tests. 

Before starting, you must determine whether the compound to be tested already has enough enolic character in acid solution to give a positive ferric chloride test. Dissolve 1 or 2 drops of the imknown liquid or a few crystals of the unknown solid in 1 mL of 95% ethanol, and add 1 mL of 1 M hydrochloric acid. Add 1 or 2 drops of 5% ferric chloride solution. If a burgundy, magenta, or reddish-brown color appears, the ferric hydroxamate test cannot be used. It contains enolic character (see Experiment 52F). 

Detection with iodine vapour before quantitative determination has been used frequently, e.g. analysis of lipid esters in conjunction with gas chromatographic determination [187] or with colorimetric determination after conversion to ferric hydroxamate complexes [731] to detect analgesic drugs [215] (cf.Fig. 79) and steroids [217, 437] with subsequent spectrophotometric determination in the visible or UV regions to detect phospholipids, where phosphorus determination followed [6, 79, 637]. 

The color duration depends on the concentration [Fe +] and the pH of the solution. The optimal value of the latter is located in the range 1.2-1.3. The characterization and quantitative analysis (through absorption measurements) of compounds that can be transformed into hydroxamic acids benefit from the formation of ferric hydroxamates. This is the case with... 

The formed aldehyde, treated by phenylsulfohydroxamic acid in the presence of a ferric salt, offers the usual ferric hydroxamate complex. Phenylsulfohydroxamic acid gives sulfinic acid and nitroxyl (unstable intermediary of structure HNO) in basic medium. Nitroxyl is a nucleophilic species that attacks the carbonyl group of carboxaldehyde. A hydroxynitroso derivative forms. It is in tautomeric equilibrium with hydroxamic acid responsible for the color ... 

The formation of ferric hydroxamate permits the quantitative determination of pilocarpine ... 

Mnemonic for ferric hydroxamate uptake. Synonym with ton A. 

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