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991.
El-Zaria ME 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(1):216-221
Charge transfer complexes (CTC) of 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetra(4-tolyl)porphyrin (TTP), 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMP), Zn-5,10,15,20-tetraphenylporphyrin (Zn-TPP), and Zn-5,10,15,20-tetra(4-tolyl)porphyrin (Zn-TTP) with tetracyanoethylene (TCNE) have been studied at various temperatures in CH(2)Cl(2) and CCl(4). The data are discussed in terms of equilibrium constant (K(CT)), molar extinction coefficient (varepsilon(CT)), thermodynamic standard reaction quantities (DeltaG degrees , DeltaH degrees and DeltaS degrees ), oscillator strength (f), and transition dipole moment (mu). The spectrum obtained for TPP/TCNE, TTP/TCNE, and TMP/TCNE systems shows two main absorption bands at 475 and 690nm, which are not due to the absorption of any of the reactants. These bands are characteristic of an intermolecular charge transfer involving the overlap of the lowest unoccupied molecular orbital (LUMO) of the acceptor with the highest occupied molecular orbital (HOMO) of the donor. The results reveal that the interaction between the donors and acceptor is due to pi-pi(*) transitions by the formation of radical ion pairs. The stoichiometry of the complexes was found to be 1:1 ratio by the Job and straight line methods between donors and acceptor with the maximum absorption bands at wavelengths of 475 and 690nm. The observed data show salvation effects on the spectral and thermodynamics properties of CTC. The ionization potential of the donors and the dissociation energy of the CTC were also determined and are found to be constant. 相似文献
992.
Mohamed GG Szesni N Fischer H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(1):161-168
The fragmentation pathways of allenylidene and carbene complexes have been studied using FAB mass spectrometry in comparison with thermal analyses (TGA, DrTG and DTA). Both the decomposition modes are investigated and the possible fragmentation pathways are suggested. The use of mass and thermal analyses (TGA and DTA) in the analyses of allenylidene and carbene complexes allowed the characterization of the fragmentation pathways in MS. The major pathway includes successive loss of carbon monoxide followed by fragmentation of the organic part of the allenylidene or carbene molecules. This is also confirmed by thermogravimetric analysis (TGA) where the first step involves the loss of carbon monoxide followed by the organic ligand. The nature of each step; exothermic or endothermic, is also studied using DTA technique. The kinetic parameters of the thermal decomposition are also studied using the Coates-Redfern method. 相似文献
993.
Abdel-Wadood HM Mohamed NA Mahmoud AM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(3):564-570
Two simple and sensitive spectrofluorometric methods have been developed and validated for determination of amlodipine besylate (AML) in tablets. The first method was based on the condensation reaction of AML with ninhydrin and phenylacetaldehyde in buffered medium (pH 7.0) resulting in formation of a green fluorescent product, which exhibits excitation and emission maxima at 375 and 480 nm, respectively. The second method was based on the reaction of AML with 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl) in a buffered medium (pH 8.6) resulting in formation of a highly fluorescent product, which was measured fluorometrically at 535 nm (lambda(ex), 480 nm). The factors affecting the reactions were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9949-0.9997) were found between the fluorescence intensity and the concentrations of AML in the concentration range of 0.35-1.8 and 0.55-3.0 microg ml(-1) for ninhydrin and NBD-Cl methods, respectively. The limits of assays detection were 0.09 and 0.16 microg ml(-1) for the first and second method, respectively. The precisions of the methods were satisfactory; the relative standard deviations were ranged from 1.69 to 1.98%. The proposed methods were successfully applied to the analysis of AML in pure and pharmaceutical dosage forms with good accuracy; the recovery percentages ranged from 100.4-100.8+/-1.70-2.32%. The results were compared favorably with those of the reported method. 相似文献
994.
Rapid screening of membrane protein activity: electrophysiological analysis of OmpF reconstituted in proteoliposomes 总被引:1,自引:0,他引:1
Solvent-free planar lipid bilayers were formed in an automatic manner by bursting of giant unilamellar vesicles (GUVs) after gentle suction application through micron-sized apertures in a borosilicate glass substrate. Incubation of GUVs with the purified ion channel protein of interest yielded proteoliposomes. These proteoliposomes allow for immediate recording of channel activity after GUV sealing. This approach reduces the time-consuming, laborious and sometimes difficult protein reconstitution processes normally performed after bilayer formation. Bilayer recordings are attractive for investigations of membrane proteins not accessible to patch clamp analysis, like e.g. proteins from organelles. In the presented work, we show the example of the outer membrane protein OmpF from Escherichia coli. We reconstituted OmpF in proteoliposomes and observed the characteristic trimeric conductance levels and the typical gating induced by pH and transmembrane voltage. Moreover, OmpF is the main entrance for beta-lactam antibiotics and we investigated translocation processes of antibiotics and modulation of OmpF by spermine. We suggest that the rapid formation of porin containing lipid bilayers is of potential for the efficient electrophysiological characterization of the OmpF protein, for studying membrane permeation processes and for the rapid screening of antibiotics. 相似文献
995.
Nouria A. Al-Awadi Maher R. Ibrahim Ismail A. Abdelhamid Mohamed H. Elnagdi 《Tetrahedron》2008,64(35):8202-8205
Arylhydrazonals were added to acrylonitrile or methyl vinyl ketone in the presence of DABCO or benzotriazole to yield the intermediate Baylis-Hillman adduct that cyclized under the reaction conditions with water elimination to yield dihydropyridazines. A pyridazine reacted with DMAD to yield a pyridine via a [4+2] Diels-Alder addition followed by retro Diels-Alder elimination of methylene aniline. Two pyridazines were condensed with DMFDMA to yield the corresponding enaminones that reacted with NH2NH2 to afford the pyrazolylpyridazines. 相似文献
996.
Palladium catalyzed cross-coupling of 3-amino- and 3-acylamido-2-bromopyridines 1a-f with triethyl phosphite allowed the synthesis of 3-amino- and 3-acylamido pyridine-2-phosphonic acid diethyl esters 2a-f, whereas nickel catalysts, although providing access to related anilido-2-phosphonates, proved inactive. Reduction of the aminophosphonate 2a with LiAlH4 afforded 3-amino-2-phosphinopyridine (3a), which was cyclocondensed with dimethylformamide dimethyl acetal (DMFA) via phosphaalkene intermediates 4a to the novel pyrido[b]-anellated 1,3-azaphosphole 5a. Reaction of amidophosphonates 2b-f with LiAlH4 did not result in the expected reductive cyclization, as shown by closely related anilido-2-phosphonates, but led to product mixtures containing N-secondary 3-amino-2-phosphinopyridines 3b-f as the main or major component. The conversion of 3b,d,e with DMFA to 5b,d,e provides first examples of N-substituted pyrido[b]-anellated azaphospholes. Structures were confirmed by multinuclear NMR and X-ray crystallography (for 2c, 3b). 相似文献
997.
Mohamed Salah K. Youssef Ragaa A. Ahmed Mohamed S. Abbady Shawkat A. Abdel-Mohsen Ahmed A. Omar 《Monatshefte für Chemie / Chemical Monthly》2008,45(8):553-559
4-(2-Aminothiazol-4-yl)-3-methyl-5-oxo-1-phenyl-2-pyrazoline was synthesized via the reaction of 4-bromoacetyl-3-methyl-5-oxo-1-phenyl-2-pyrazoline with thiourea [7] and was transformed to related fused
heterocyclic systems. The antifungal and antibacterial studies revealed in some cases excellent biocidal properties. 相似文献
998.
Emad M. El-Telbani Mohamed F. El Shehry Galal A. M. Nawwar 《Monatshefte für Chemie / Chemical Monthly》2008,387(2):685-689
Synthesis of the title ring system is described using ethyl 4-(2,4-dichlorophenoxy)-3-oxobutanoate as starting material. The
latter was prepared through acylating Meldrum’s acid with the phenoxy acid chloride derivative. 相似文献
999.
Summary. Several derivatives of 5-arylmethylenebis(1-methyl-6-amino-2-thiouracils) and 5-aryldipyrimidopyridines were prepared by stirring
of 6-amino-1-methyl-2-thiouracil and 6-amino-1-benzyluracil with different aromatic aldehydes in ethanol in the presence of
HCl or refluxing with AcOH. On the other hand, 6-alkylthio-3,9-dimethylpurine-2-ones were synthesized by the alkylation of 3,9-dimethyl-6-thioxanthine
which was prepared by treatment of 3,9-dimethylxanthine with P2S5. The structures of the novel compounds were characterized by spectroscopic methods. The effects of the novel compounds on
both HAV and HSV type 1 were investigated. Also, some compounds showed inhibitory effects on Gram-positive and Gram-negative bacteria as well as yeast and fungi.
On leave from Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt 相似文献
1000.
Bakr F. Abdel-Wahab Salwa F. Mohamed Abd El-Galil E. Amr Mohamed M. Abdalla 《Monatshefte für Chemie / Chemical Monthly》2008,139(9):1083-1090
Methyl 2-(thiazol-2-ylcarbamoyl)acetate was synthesized and used as starting material. It was treated with hydrazine hydrate
to afford the hydrazide, which was reacted with nitromethane and formaldehyde to give the saturated nitropyrimidine. The hydrazide
was reacted with phenyl isothiocyanate to afford the thiosemicarbazide, which was cyclized with ethyl bromoacetate, sodium
hydroxide, or sulfuric acid to afford N-phenylthiazolidinone, N-phenyltriazole, and thiadiazolyl derivatives. The methyl 2-(thiazol-2-ylcarbamoyl)acetate was coupled with diazonium salts
of aniline, 4-chloroaniline, 4-bromoaniline, or 4-aminobenzenesulfonamide to afford the carbamoyl acetates, which were reacted
with 2-aminobenzimidazole, 1,2,4,5-tetrachlorophthalic anhydride, and hydrazine hydrate to afford the corresponding thiazolylmalonamide,
tetrachloroisoindolylimide, and tri-azole derivatives. Schiff bases and imides are newly synthesized candidates obtained via simple condensation of the hydrazide with aldehydes, 2,3-pyridinedicarboxylic anhydride, or 1,8-naphthalenedicarboxylic anhydride.
The pharmacological screening showed that many of these compounds have good antihypertensive α-blocking activity and low toxicity.
Correspondence: Abd El-Galil E. Amr, National Research Center, Applied Organic Chemistry, Dokki, Cairo, Egypt. 相似文献