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161.
Somesh Singh Rishi. K. Vishwakarma R. J. Santosh Kumar Prashant D. Sonawane Ruby Bashir M. Khan 《Applied biochemistry and biotechnology》2013,170(3):729-741
Glycosylation of flavonoids is mediated by family 1 uridine diphosphate (UDP)-dependent glycosyltransferases (UGTs). Until date, there are few reports on functionally characterized flavonoid glycosyltransferases from Withania somnifera. In this study, we cloned the glycosyltransferase gene from W. somnifera (UGT73A16) showing 85–92 % homology with UGTs from other plants. UGT73A16 was expressed as a His6-tagged fusion protein in Escherichia coli. Several compounds, including flavonoids, were screened as potential substrates for UGT73A16. HPLC analysis and hypsochromic shift indicated that UGT73A16 transfers a glucose molecule to several different flavonoids. Based on kinetic parameters, UGT73A16 shows more catalytic efficiency towards naringenin. Here, we explored UGT73A16 of W. somnifera as whole cell catalyst in E. coli. We used flavonoids (genistein, apigenin, kaempferol, naringenin, biochanin A, and daidzein) as substrates for this study. More than 95 % of the glucoside products were released into the medium, facilitating their isolation. Glycosylation of substrates occurred on the 7- and 3-hydroxyl group of the aglycone. UGT73A16 also displayed regiospecific glucosyl transfer activity towards 3-hydroxy flavone compound, which is the backbone of all flavonols and also for a chemically synthesized compound, not found naturally. The present study generates essential knowledge and molecular as well as biochemical tools that allow the verification of UGT73A16 in glycosylation. 相似文献
162.
1,1′‐Ferrocene dicarbonyl chloride was prepared by an improved and efficient conversion method from 1,1′‐ferrocene dicarboxylic acid and reacted by esterification with p‐nitrophenol, followed by reduction, to form a ferrocene‐based diamine, 1,1′‐ferrocene bis (p‐amino phenylate). The diamine was characterized by elemental analysis, 1H NMR, and Fourier transform infrared (FTIR) spectroscopy and subsequently condensed with 1,1′‐ferrocene dicarbonyl chloride to form a novel main chain ferrocene‐containing polyamide, poly{imino ferrocene bis (p‐amino phenylate) ferrocenyl}. Its polymeric nature was confirmed by its physical properties, elemental analysis, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetric studies. 相似文献
163.
Tariq Bashir Majid Ali Sung‐Woo Cho Nils‐Krister Persson Mikael Skrifvars 《先进技术聚合物》2013,24(2):210-219
The functionalization of textile fibers with intrinsically conductive polymers has become a prominent research area throughout the world. A number of coating techniques have already been utilized and optimized to get the uniform layers of conductive polymers on the surface of different substrates. In our previous study, we produced poly(3,4‐ethylenedioxythiophene) (PEDOT)‐coated conductive fibers by employing oxidative chemical vapor deposition (oCVD) technique. This paper describes the effects of pre‐treatment steps, such as surface treatment of textile fibers with organic solvents, drying of oxidant‐enriched fibers at variable temperatures and time, and oxidant type on the electrical, mechanical, and thermal properties of PEDOT‐coated conductive fibers. Two well‐known oxidants, ferric(III)chloride and ferric(III)p‐toluenesulfonate (FepTS), were studied, and then their results were compared. In order to verify the PEDOT‐coated layer and, to some extent, its impregnation inside the viscose yarns, a morphological study was carried out by using the attenuated total reflectance Fourier transform infrared spectroscopic imaging technique and computed tomography scanning across the obtained conductive fibers. Differential scanning calorimetric and thermogravimetric analysis were utilized to investigate the thermal properties and the contents of PEDOT in PEDOT‐coated fibers. The mechanical properties of conductive fibers were evaluated by tensile strength testing of produced fibers. Effects of all of these pre‐treatment steps on electrical properties were analyzed with Kiethly picoammeter. This study cannot only be exploited to improve the properties of conductive fibers but also to optimize the oCVD process for the production of conductive textile fibers by coating with different conjugated polymers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
164.
Bashir Ahmad Dar Mohd. Mohsin Abdul Basit Mazahar Farooqui 《Journal of Saudi Chemical Society》2013,17(2):177-180
The aim of this work is to develop a cheap and green chemical process and this paper describes the catalytic commotion of locally collected sand in Friedel–Craft's Acylation of aromatic compounds like benzene, anisole, aniline, naphthalene and phenol etc. The sand consists of silica and alumina as analyzed by means of EDAX and acts as a green Lewis acid. The catalyst was also characterized by using BET, SEM, and XRD techniques. 相似文献
165.
Several classes of congruence-simple semirings are characterized and various further examples are constructed. Among others,
it is shown that every congruence-simple semiring fits into one of the following three classes: additively idempotent semirings,
additively cancellative semirings, additively nil-semirings of index 2. 相似文献
166.
Lidstone EA Chaudhery V Kohl A Chan V Wolf-Jensen T Schook LB Bashir R Cunningham BT 《The Analyst》2011,136(18):3608-3615
We introduce photonic crystal enhanced microscopy (PCEM) as a label-free biosensor imaging technique capable of measuring cell surface attachment and attachment modulation. The approach uses a photonic crystal optical resonator surface incorporated into conventional microplate wells and a microscope-based detection instrument that measures shifts in the resonant coupling conditions caused by localized changes in dielectric permittivity at the cell-sensor interface. Four model systems are demonstrated for studying cancer cells, primary cardiac muscle cells, and stem cells. First, HepG2/C3 hepatic carcinoma cells were cultured and observed via PCEM in order to characterize cell adhesion in the context of growth and locomotion. Second, Panc-1 pancreatic cancer cells were used to verify that cell attachment density decreases in response to staurosporine, a drug that induces apoptosis. Third, we used PCEM to confirm the influence of integrin-mediated signaling on primary neonatal cardiomyocyte growth and development. Rounded cardiomyocytes consistently showed decreased cell attachment density as recorded via PCEM, while spreading cells exhibited greater attachment strength as well as increased contractility. Finally, PCEM was used to monitor the morphological changes and extracellular matrix remodeling of porcine adipose-derived stem cells subjected to a forced differentiation protocol. Each of these experiments yielded information regarding cell attachment density without the use of potentially cytotoxic labels, enabling study of the same cells for up to several days. 相似文献
167.
Non-thermal and thermal processes due to femtosecond laser ablation of aluminum (Al) at low, moderate, and high-fluence regimes are identified by Atomic Force Microscope (AFM) surface topography investigations. For this purpose, surface modifications of Al by employing 25 fs Ti: sapphire laser pulses at the central wavelength of 800 nm have been performed to explore different nano- and microscale features such as hillocks, bumps, pores, and craters. The mechanism for the formation of these diverse kinds of structures is discussed in the scenario of three ablation regimes. Ultrafast electronic and non-thermal processes are dominant in the lower fluence regime, whereas slow thermal processes are dominant at the higher fluence regime. Therefore, by starting from the ablation threshold three different fluence regimes have been chosen: a lower fluence regime (0.06–0.5 J cm?2 single-shot irradiation under ultrahigh vacuum condition and 0.25–2.5 J cm?2 single-shot irradiation in ambient condition), a moderate-fluence regime (0.25–1.5 J cm?2 multiple-shot irradiation), and a high-fluence regime 2.5–3.5 J cm?2 multiple-shot irradiation. For the lower fluence (gentle ablation) regime, around the ablation threshold, the unique appearance of individual, localized Nano hillocks typically a few nanometers in height and less than 100 nm in diameter are identified. These Nano hillock-like features can be regarded as a nonthermal, electronically induced phase transition process due to localized energy deposition as a result of Coulomb explosion or field ion emission by surface optical rectification. At a moderate-fluence regime, slightly higher than ablation threshold multiple-pulse irradiation produces bump-formation and is attributed to ultrafast melting (plasma formation). The high-fluence regime results in greater rates of material removal with highly disturbed and chaotic surface of Al with an appearance of larger protrusions at laser fluence well above the ablation threshold. These nonsymmetrical shapes due to inhomogeneous nucleation, cluster formation, and resolidification of a metallic surface after melting are attributable to slow thermal processes (ps time scale). 相似文献
168.
Bashir Ahmad 《Results in Mathematics》2013,63(1-2):183-194
In this paper, we prove the existence of solutions of a nonlocal boundary value problem for nonlinear integro-differential equations of fractional order given by $$ \begin{array}{ll} ^cD^qx(t) = f(t,x(t),(\phi x)(t),(\psi x)(t)), \quad 0 < t < 1,\\x(0) = \beta x(\eta), x'(0) =0, x''(0) =0, \ldots, x^{(m-2)}(0) =0, x(1)= \alpha x(\eta), \end{array}$$ where $${q \in (m-1, m], m \in \mathbb{N}, m \ge 2}$, $0< \eta <1$$ , and ${\phi x}$ and ${\psi x}$ are integral operators. The existence results are established by means of the contraction mapping principle and Krasnoselskii’s fixed point theorem. An illustrative example is also presented. 相似文献
169.
Bashir Ahmad Sotiris K. Ntouyas Ahmed Alsaedi 《Journal of Applied Mathematics and Computing》2017,53(1-2):129-145
In this paper, we establish sufficient conditions for the existence and uniqueness of solutions for a boundary value problem of fractional differential equations with nonlocal and average type integral boundary conditions. The Leray–Schauder nonlinear alternative, Krasnoselskii’s fixed point theorem and Banach’s fixed point theorem together with Hölder inequality are applied to construct proofs for the main results. Examples illustrating the obtained results are also presented. 相似文献
170.
Rasha F. Al‐Bashir Nouria A. Al‐Awadi Osman M. E. El‐Dusouqui 《Journal of Physical Organic Chemistry》2011,24(4):311-319
Fourteen ketone/thione‐stabilized triphenylphosphonium methylides were subjected to conventional gas‐phase and flash vacuum pyrolysis (FVP). The kinetics of the first‐order thermal gas‐phase reactions of all these compounds were investigated over 360–653 K temperature range. The values of the Arrhenius log A and energy of activation of these ylides averaged 11.52 ± 0.34 s?1 and 133.20 ± 3.14 kJ mol?1, respectively. The products of sealed‐tube (static) and FVP were analyzed and compared. A mechanism is proposed to account for the products of reaction. The rate constants [k (s?1)] of the substrates at 500 K were calculated and used to substantiate the proposed mechanism of pyrolysis, and to rationalize the thermal gas‐phase reactivities of the ylides under study. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献