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181.
Hussein YH Anderson N Lian TT Abdou IM Strekowski L Timoshchuk VA Vaghefi MM Netzel TL 《The journal of physical chemistry. A》2006,110(13):4320-4328
The goal of this work is to produce high yields of long-lived AQ(*-)/dA(*+) charge transfer (CT) excited states (or photoproducts). This goal fits within a larger context of trying generally to produce high yields of long-lived CT excited states within DNA nucleoside conjugates that can be incorporated into DNA duplexes. Depending upon the energetics of the anthraquinonyl (AQ) (3)(pi,pi) state as well as the reduction potentials of the subunits in particular anthraquinonyl-adenine conjugates, CT quenching of the AQ (3)(pi,pi*) state may or may not occur in polar organic solvents. In MeOH, bis(3',5'-O-acetyl)-N(6)-(anthraquinone-2-carbonyl)-2'-deoxyadenosine (AQCOdA) behaves as intended and forms a (3)(AQ(*-)/dA(*+)) CT state with a lifetime of 3 ns. However, in nonpolar THF the AQ(*-)/dA(*+) CT states of AQCOdA are too high in energy to be formed, and in DMSO a (1)(AQ(*-)/dA(*+)) CT state is formed but lives only 6 ps. Although the lowest energy excited state for AQCOdA in MeOH is a (3)(AQ(*-)/dA(*+)) CT state, for N(6)-(anthraquinone-2-methylenyl)-2'-deoxyadenosine (AQMedA) in the same solvent it is a (3)(pi,pi*) state. Changing the linking carbonyl in AQCOdA to methylene in AQMedA makes the anthraquinonyl subunit harder to reduce by 166 mV. This raises the energy of the (3)(AQ(*-)/dA(*+)) CT state above that of the (3)(pi,pi*) in AQMedA. The conclusion is that anthraquinonyl-dA conjugates will not have lowest energy AQ(*-)/dA(*+) CT states in polar organic solvents unless the anthraquinonyl subunit is also substituted with an electron-withdrawing group that raises the AQ-subunit's reduction potential above that of AQ. A key finding in this work is that the lifetime of the (3)(AQ(*-)/dA(*+)) CT excited state (ca. 3 ns) is ca. 500-times longer than that of the corresponding (1)(AQ(*-)/dA(*+)) CT excited state (ca. 6 ps).' 相似文献
182.
A nonavalent glycodendrimer bearing terminal alpha-d-mannopyranoside units has been synthesized with a convergent approach. Terminal trivalent mannoside dendrons bearing p-halophenyl ethers were prepared by glycosylation of pentaerythritol derivatives having three 2-hydroxyethyl ether substituents. Two efficient routes were developed for the synthesis of the pentaerythritol-based core (17), which has three terminal propargyl ethers. Conditions were found under which the triple Sonogashira coupling reaction of the dendron and the tri-O-propargyl ether (17) proceeded efficiently. The product was deprotected and it and precursors were fully characterized by NMR spectroscopy and FT-ICR mass spectrometry. 相似文献
183.
Ruiz C Parikh A José J Buchmann L Caggiano JA Chen AA Clark JA Crawford H Davids B D'Auria JM Davis C Deibel C Erikson L Fogarty L Frekers D Greife U Hussein A Hutcheon DA Huyse M Jewett C Laird AM Lewis R Mumby-Croft P Olin A Ottewell DF Ouellet CV Parker P Pearson J Ruprecht G Trinczek M Vockenhuber C Wrede C 《Physical review letters》2006,96(25):252501
The strength of the Ec.m. = 184 keV resonance in the 26gAl(p, gamma)27 reaction has been measured in inverse kinematics using the DRAGON recoil separator at TRIUMF's ISAC facility. We measure a value of omega gamma = 35 +/- 7 microeV and a resonance energy of Ec.m. = 184 +/- 1 keV, consistent with p-wave proton capture into the 7652(3) keV state in 27Si, and discuss the implications of these values for 26GAl nucleosynthesis in typical oxygen-neon white-dwarf novae. 相似文献
184.
Ahmed M. Hussein 《Journal of Saudi Chemical Society》2010,14(1):61-68
An easy and efficient route for the synthesis of some tetrazolo[1,5-a]-, pyrazolo[1,5-a]- and pyrimido[1,6-a] pyrimidine derivatives was described through the reaction of sodium salts of formyl ketones with 5-aminotetrazole, 5-aminopyrazole derivatives and 6-aminothiouracil, respectively. The antimicrobial screening of some derivatives of the prepared compounds has been achieved, and it exhibited a moderate activity against the tested microorganisms. 相似文献
185.
186.
Hussein Samma Chee Peng Lim Junita Mohamad Saleh Shahrel Azmin Suandi 《Memetic Computing》2016,8(3):235-251
In this paper, a novel fuzzy support vector machine (FSVM) coupled with a memetic particle swarm optimization (MPSO) algorithm is introduced. Its application to a license plate recognition problem is studied comprehensively. The proposed recognition model comprises linear FSVM classifiers which are used to locate a two-character window of the license plate. A new MPSO algorithm which consists of three layers i.e. a global optimization layer, a component optimization layer, and a local optimization layer is constructed. During the construction process, MPSO performs FSVM parameters tuning, feature selection, and training instance selection simultaneously. A total of 220 real Malaysian car plate images are used for evaluation. The experimental results indicate the effectiveness of the proposed model for undertaking license plate recognition problems. 相似文献
187.
188.
Mohammed A. Al-Nuri Mohammed A. Hannoun Nidal A. Zatar Maher A. Abu-Eid Waheed J. Al-Jondi Ahmad I. Hussein 《光谱学快报》2013,46(4):409-416
A new method for isolation and spectrophotometric determination of plumbagin is presented. Plumbagin was isolated by thin layer chromatography (TLC) and column chromatography (CC) techniques, as an orange tinged yellow long crystalline substances. Plumbagin exhibits two absrop-tion maxima at 410 and 510 nm. Stability of the color, pKa value, and the effect of pH were studied. Beer's law is obeyed over the range 0.9-45 ppm. The method is applied to the determination of plumbagin in roots, stems, and leaves of Plumbago europaea L. plant. 相似文献
189.
Ammonium and nitrate ion-selective electrodes were applied as sensors in bacterial growth curves for the isolation of nitrate and nitrite reductase. A nitrate ion-selective electrode was used as a successful new technique for the assay of nitrate reductase activity: the decrease in nitrate concentration was followed continuously. Likewise, an ammonium ion-selective electrode was used to follow the increase in ammonium ion concentration. Excellent agreement with spectrophotometric procedures ( < 5%) was obtained. 相似文献
190.
Nitrate ion-selective electrodes were successfully applied both in stationary solutions and in flow streams as new analytical techniques for the assay of nitrate reductase activity. An ammonium-selective electrode was similarly used to measure the increase in ammonium ion concentration during the enzymatic reduction of nitrate to ammonium. Preliminary studies on a true enzyme electrode for assay of nitrate ion are discussed. 相似文献