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161.
Devkota KP Choudhary MI Nawaz SA Lannang AM Lenta BN Fokou PA Sewald N 《Chemical & pharmaceutical bulletin》2007,55(4):682-684
The microbial transformation of a steroidal alkaloid, dictyophlebine (1) with Rhizopus stolonifer (ATCC 10404) afforded three oxidized metabolites 2-4. Compound 2 was found to be a new product. These metabolites were structurally characterized on the basis of modern spectroscopic techniques. Their inhibitory activity towards acetyl- and butyrylcholinesterase has been evaluated and the new product 2 has been found to be more potent than the parent compound and other metabolites. 相似文献
162.
The present research work is concerned with the biotransformation of l-tyrosine to dopamine (DA) by calcium alginate entrapped conidiospores of a mutant strain of Aspergillus oryzae. Different strains of A. oryzae were isolated from soil. Out of 13 isolated strains, isolate-2 (I-2) was found to be a better DA producer. The wild-type I-2 was chemically improved by treating it with different concentrations of ethyl methyl sulfonate (EMS). Among seven mutant variants, EMS-6 exhibiting maximal DA activity of 43 μg/ml was selected. The strain was further exposed with l-cysteine HCl to make it resistant against diversion and environmental stress. The conidiospores of selected mutant variant A. oryzae EMS-6 strain were entrapped in calcium alginate beads. Different parameters for immobilization were investigated. The activity was further improved from 44 to 62 μg/ml under optimized conditions (1.5 % sodium alginate, 2 ml inoculum, and 2 mm bead size). The best resistant mutant variable exhibited over threefold increase in DA activity (62 μg/ml) than did wild-type I-2 (21 μg/ml) in the reaction mixture. From the results presented in the study, it was observed that high titers of DA activity in vitro could effectively be achieved by the EMS-induced mutagenesis of filamentous fungus culture used. 相似文献
163.
A structural investigation of heteroleptic pentavalent antimonials and their leishmanicidal activity
Rabia Mushtaq Muhammad Khawar Rauf Marcus Bond Amin Badshah Muhammad Irshad Ali Akhtar Nadhman Masoom Yasinzai Muhammad Nawaz Tahir 《应用有机金属化学》2016,30(6):465-472
In the quest for new drug candidates for the safe treatment of parasitic diseases like leishmaniasis, a series of heteroleptic pentavalent antimonials of the type [SbR3(OOCR′)2] were synthesized and characterized using elemental analysis, Fourier transform infrared spectroscopy and multinuclear (1H and 13C) NMR spectroscopy. The carboxylate moieties are predominantly substituted benzoates with some complexes that fit in acetato or nicotinato ligands. The crystal structures of [Sb(p‐Tol)3(p‐CH3C6H4COO)2], [Sb(p‐Tol)3(3,5‐Cl2C6H3COO)2] and [Sb(p‐Tol)3(3‐nicotinato)2] were determined crystallographically and shown to adopt geometries intermediate between trigonal bipyramidal and square pyramidal, and essentially monomeric with a five‐coordinated Sb center. The leishmanicidal activity was assessed against the Leishmania tropica KWH23 parasite, and the cytotoxicity level was also measured on human macrophage blood cells. It was observed that IC50 of the antimonials was 100‐fold superior as compared with the standard antimonial drug used. Cytotoxicity results showed that these antimonials are highly active even at low concentrations and are biocompatible with human macrophages, making them highly promising drug candidates for further investigation. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
164.
Sahoo JK Tahir MN Yella A Branscheid R Kolb U Tremel W 《Langmuir : the ACS journal of surfaces and colloids》2011,27(1):385-391
A major drawback in the application of layered chalcogenide nanoparticles/tubes is their inertness to chemical and biological modification and functionalization. Their potential use in composite materials might be greatly enhanced by improving the chalcogenide/matrix interface bonding. A novel modification strategy for layered chalcogenide nanoparticles based on the chalcophilic affinity of metals and the chelating terpyridine is reported. The terpyridine anchor group can be conjugated to fluorescent tags or hydrophilic/hydrophobic groups that confer solubility in various solvents to the otherwise insoluble chalcogenide nanoparticles. The functionalized particles are characterized using TEM/HRTEM, optical and vibrational spectroscopy, and confocal laser scanning microscopy. 相似文献
165.
166.
The present analysis deals with diffraction of acoustic waves by an oscillating strip focusing on the exact and concise formulation of a series solution in the complex domain. The complete solution is represented by a series, the eigenfunctions of which are generalized gamma functions. An exact expression of this special function, with argument being ‘integer +1/2’, is derived. The convergence analysis of the series solution in transformed domain is discussed graphically. Finally, the scattered and total acoustic fields are obtained by exact and asymptotic evaluations of inverse Fourier transforms. The significance of the present investigation is the derivation of a high order accurate solution in a convenient form. 相似文献
167.
The problem of reconstructing the spatial support of an extended radiating electric current source density in a lossy dielectric medium from transient boundary measurements of the electric fields is studied. A time reversal algorithm is proposed to localize a source density from loss-less wave-field measurements. Further, in order to recover source densities in a lossy medium, we first build attenuation operators thereby relating loss-less waves with lossy ones. Then based on asymptotic expansions of attenuation operators with respect to attenuation parameter, we propose two time reversal strategies for localization. The losses in electromagnetic wave propagation are incorporated using the Debye's complex permittivity, which is well-adopted for low frequencies (radio and microwave) associated with polarization in dielectrics. 相似文献
168.
169.
This investigation explores the characteristics of melting heat transfer in a boundary layer flow of the Jeffrey fluid near the stagnation point on a stretching sheet subject to an applied magnetic field. The governing boundary layer equations are transformed to ordinary differential equations by similarity transformations. Resulting nonlinear problems are solved analytically by the homotopy analysis method. It is noticed that an increase in the melting parameter decreases the dimensionless velocity and temperature, while an increase in the Deborah number increases the velocity and momentum boundary layer thickness. 相似文献
170.
Solution of fractional-order integro-differential equations using optimal homotopy asymptotic method
Nawaz Rashid Khattak Abraiz Akbar Muhammad Ahsan Sumbal Shah Zahir Khan Adam 《Journal of Thermal Analysis and Calorimetry》2021,146(3):1421-1433
Journal of Thermal Analysis and Calorimetry - In this article, a semi-analytical technique called optimal homotopy asymptotic method (OHAM) is presented for numerical solutions of fractional-order... 相似文献