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Waleed E. Mahmoud A.A. Al-Ghamdi Mohammad W. Kadi 《Radiation Physics and Chemistry》2012,81(6):693-696
This contribution represents the manufacturing of a hybrid organic–inorganic proton conducting compound, which involves the introduction of heteropoly acid (HPA) of different concentrations into poly-vinyl alcohol (PVA). These compounds were irradiated by γ-rays at different doses of 10, 20, 30, and 40 kGy. The unirradiated and irradiated compounds were characterized by XRD and DSC. The XRD results showed that the crystallinity and d-spacing were strongly influenced by the amount of HPA and irradiation doses. The DSC results showed that the melting point was decreased as a result of HPA concentration and irradiation doses. The degree of crystallinity calculated from XRD is in good agreement with that calculated from DSC. The activation energy of the Unirradiated and irradiated compounds was calculated using the Flynn–Wall–Ozawa model. 相似文献
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Solvent-free Claisen-Schmidt reactions of cycloalkanones with various substituted benzaldehydes (aryl aldehydes) using solid NaOH (20 mol%) and applying a grinding technique were studied. Quantitative yields (96-98%) of α,α'-bis-(substituted-benzylidene)cycloalkanones were obtained. Aliphatic aldehydes also provided α,α'-bis-(substituted-alkylidene)cycloalkanones in very good yields with minor amounts of a-(substituted-alkylidene)cycloalkanones. The catalytic performance of solid NaOH was examined. The molar ratio of NaOH was optimized. The catalytic effect of solid NaOH was also evaluated by comparing it with KOH, NaOAc, and NH(4)OAc and it turns out that 20 mol% of solid NaOH was good enough to catalyze the Claisen-Schmidt reactions of cycloalkanones with various substituted benzaldehydes. Additionally, the regioselectivity of the Claisen-Schmidt reaction of acetone with benzaldehyde was examined. Using the same method, we could synthesize the corresponding bis-benzylidene- and mono-benzylideneacetone separately in 98% and 96% yields, respectively. 相似文献
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Zdenk ezá und Karel Kadi 《Fresenius' Journal of Analytical Chemistry》1962,190(3):305-309
Zusammenfassung Es wird eine photometrische Bestimmung des Nitrat- und Gesamtstickstoffes in Kammerschwefelsäure beschrieben, die auf der Ntrierung der Salicylsäure und Messung der gelben Farbe des Nitrierungsproduktes in alkalischer Lösung beruht. Die Methode ist einfach, schnell und für Serienuntersuchungen geeignet.Wir danken dem Fräulein D. Myslivcová für ihre unermüdliche Mitarbeit 相似文献
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Oves-Costales D Kadi N Fogg MJ Song L Wilson KS Challis GL 《Chemical communications (Cambridge, England)》2008,(34):4034-4036
The AsbB enzyme, which is involved in the biosynthesis of the virulence-conferring siderophore petrobactin in Bacillus anthracis, is shown to catalyze efficient ATP-dependent condensation of spermidine, but not N(1)-(3,4-dihydroxbenzoyl)-spermidine, with N(8)-citryl-spermidine or N(1)-(3,4-dihydroxbenzoyl)-N(8)-citryl-spermidine, suggesting that N(1)-(3,4-dihydroxbenzoyl)-spermidine is very unlikely to be a significant intermediate in petrobactin biosynthesis, contrary to previous suggestions. 相似文献
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Kadi N Arbache S Song L Oves-Costales D Challis GL 《Journal of the American Chemical Society》2008,130(32):10458-10459
Putrebactin is a dihydroxamate iron chelator produced by the metabolically versatile marine bacterium Shewanella putrefaciens. It is a macrocyclic dimer of N-hydroxy-N-succinyl-putrescine (HSP) and is structurally related to desferrioxamine E, which is a macrocyclic trimer of N-hydroxy-N-succinyl-cadaverine (HSC). We recently showed that DesD, a member of the NIS synthetase superfamily, catalyzes the key step in desferrioxamine E biosynthesis: ATP-dependent trimerisation and macrocylization of HSC. Here we report identification of a conserved gene cluster in the sequenced genomes of several Shewanella species, including Shewanella putrefaciens, which is hypothesized to direct putrebactin biosynthesis from putrescine, succinyl-CoA and molecular oxygen. The pubC gene within this gene cluster encodes a protein with 65% similarity to DesD. We overexpressed pubC from Shewanella species MR-4 and MR-7 in E. coli. The resulting His6-PubC fusion proteins were purified by Ni-NTA affinity and gel filtration chromatography. The recombinant proteins were shown to catalyze ATP-dependent cyclodimerization of HSP to form putrebactin. The uncyclized dimer of HSP pre-putrebactin was shown to be an intermediate in the conversion of two molecules of HSP to putrebactin. The data indicate that pre-putrebactin is converted to putrebactin via PubC-catalyzed activation of the carboxyl group by adenylation, followed by PubC-catalyzed nucleophilic attack of the amino group on the carbonyl carbon of the acyl adenylate. This mechanism for macrocycle formation is very different from the mechanism involved in the biosynthesis of many other macrocyclic natural products, where already-activated acyl thioesters are converted by thioesterase domains of polyketide synthases and nonribosomal peptide synthetases to macrocycles via covalent enzyme bound intermediates. The results of this study demonstrate that two closely related enzymes, PubC and DesD, catalyze specific cyclodimerization and cyclotrimerization reactions, respectively, of structurally similar substrates, raising intriguing questions regarding the molecular mechanism of specificity. 相似文献
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Kadi M Hansson P Almgren M Bergström M Garamus VM 《Langmuir : the ACS journal of surfaces and colloids》2004,20(10):3933-3939
Mixtures of the partly fluorinated cationic surfactant HFDePC (N-(1, 1,2,2-tetrahydroperfluorodecanyl)-pyridinium chloride and deuterated headgroup) with C16TAC, hexadecyl-trimethylammonium chloride, have been investigated using small angle neutron scattering with contrast matching. Earlier results from this system suggested that a demixing occurred, into two coexisting populations of micelles, hydrocarbon-rich and fluorocarbon-rich, respectively. The present results could be explained by one type of mixed micelles with an inhomogeneous distribution of fluorinated and hydrogenated surfactants within the micelles although a demixing cannot be definitely excluded. 相似文献
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A highly efficient and sensitive LC‐MS/MS method for the determination of afatinib in human plasma: application to a metabolic stability study 下载免费PDF全文
Adnan A. Kadi Ali S. Abdelhameed Hany W. Darwish Mohamed W. Attwa Nasser S. Al‐Shakliah 《Biomedical chromatography : BMC》2016,30(8):1248-1255
Afatinib (AFT) is a new tyrosine kinase inhibitor approved for the treatment of nonsmall cell lung cancer. In the present study, a simple, specific, rapid and sensitive liquid chromatography tandem mass‐spectrometric method for the quantification of AFT in human plasma, was developed and validated. Chromatographic separation of the analytes was accomplished on a reversed‐phase Luna®‐PFP 100 Å column (50 × 2.0 mm; 3.0 μm) maintained at ambient temperature. Isocratic elution was carried out using acetonitrile–water (40:60, v/v) containing 10 mm ammonium formate buffer (pH 4.5) adjusted with formic acid at a flow rate of 0.4 mL min?1. The analytes were monitored by electrospray ionization in positive ion multiple reaction monitoring mode. The method yields a linear calibration plot (r2 = 0.9997) from a quantification range of 0.5–500 ng mL?1 with the lower limit of quantification and lower limit of detection of 1.29 and 0.42 ng mL?1, respectively. The intra‐ and inter‐day precision and accuracy were estimated and found to be in the ranges of 1.53–4.11% for precision and ?2.80–0.38% for accuracy. Finally, quantification of afatinib in a metabolic stability study in rat liver microsomes was achieved through the proposed method. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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