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Samer K. Albdallah Khaleel I. Assaf Khaled Bodoor Nada A. Al-Sakhen Lama D. Malhis Akef I. Alhmaideen Musa I. El-Barghouthi 《Journal of solution chemistry》2018,47(11):1768-1778
Molecular dynamics (MD) simulations were carried out to study the host–guest complexation in aqueous solution between cucurbit[7]uril (CB7) and the neutral and protonated forms of benzimidazole derivatives. Complexation occurs via encapsulation of the hydrophobic part (benzene ring) of the guest within the CB7 hydrophobic cavity, and the interactions of the amine group(s) of the imidazole ring of the guest with the CB7 carbonyl portals. The molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) method is used to estimate the host–guest Gibbs energy of binding. The results indicate that CB7 binds the protonated form more strongly than the neutral one, and that the dominant contribution to the Gibbs energy of complexation for the neutral and protonated guests is associated, respectively, with the host–guest van der Waals and electrostatic interactions. Quantum chemical calculations using dispersion-corrected density functional theory (DFT) are used to calculate the binding affinities and to predict the pKa values of the free and complexed guests. The calculated pKa values for the free guests reveal excellent agreement with the experimental values, while for the complexed guests, general trends are obtained. 相似文献
224.
In this paper, we propose simple but effective two different fuzzy wavelet networks (FWNs) for system identification. The FWNs combine the traditional Takagi–Sugeno–Kang (TSK) fuzzy model and discrete wavelet transforms (DWT). The proposed FWNs consist of a set of if–then rules and, then parts are series expansion in terms of wavelets functions. In the first system, while the only one scale parameter is changing with it corresponding rule number, translation parameter sets are fixed in each rule. As for the second system, DWT is used completely by using wavelet frames. The performance of proposed fuzzy models is illustrated by examples and compared with previously published examples. Simulation results indicate the remarkable capabilities of the proposed methods. It is worth noting that the second FWN achieves high function approximation accuracy and fast convergence. 相似文献
225.
Preparation,properties, and antibacterial behavior of a novel cellulose derivative containing lactam groups
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Fanny Joubert Gary J. Sharples Osama M. Musa David R. W. Hodgson Neil R. Cameron 《Journal of polymer science. Part A, Polymer chemistry》2015,53(1):68-78
Lactam groups were introduced onto the backbone of hydroxyethyl cellulose (HEC) to modify properties, such as solubility in organic solvents and solution viscosity and to introduce possible antibacterial activity. Functionalization was achieved using 1‐(hydroxymethyl)‐2‐pyrrolidinone (HMP), and the functionalization reactions were investigated using NMR spectroscopy. The covalent attachment between HEC and HMP was confirmed using 1H‐13C correlated NMR experiments. Degrees of functionalization were calculated using integrated 13C NMR spectra, with values of up to 0.9 being demonstrated on the primary alcohol functionality of HEC. The functionalized HECs showed markedly different properties to unfunctionalized HEC, including the ability to swell considerably in water. Functionalized HEC displayed increased thermal stability and reduced solution viscosity compared with unfunctionalized HEC. Moreover, functionalization altered the bacterial adhesion characteristics compared with unfunctionalized HEC. © 2014 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 68–78 相似文献
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Fakhri O. Yousef Raed Ghanem Noura H. Alshraa Nosayba M. Al Omari Khaled Bodoor Musa I. El-Barghouthi 《Journal of inclusion phenomena and macrocyclic chemistry》2017,88(3-4):171-180
The spectral properties of etoricoxib (ETR) at pH 2.0, 6.0 and 10.0 in the presence of cyclodextrins (CDs) were investigated. The absorption spectrum of ETR in acidic medium exhibited two bands centered at 236 and 273 nm, while in basic medium it exhibited two bands centered at 236 and 285 nm. No change in the spectrum was observed in the presence of CDs. The fluorescence emission spectra of ETR in acidic and basic media exhibited one band at 380 nm and another one at 484 nm. The emission band at 484 nm was enhanced when ETR was complexed with β-CD and γ-CD at pH 2.0, 6.0 and 10.0, while the band at 380 nm was enhanced selectively when ETR was complexed with α-CD at pH 2.0. Molecular dynamics simulations computations revealed that at pH 2.0, the sulfonyl moiety of H2ETR2+ is preferentially included within the α-CD cavity, which is believed to cause the enhancement of the band at 380 nm. Moreover, at pH 6.0 and 10.0, the enhancement of the band at 484 nm was related to the inclusion of the chloropyridinyl and methylpyridinyl groups of the bipyridine moiety of HETR+ and ETR within β-CD and γ-CD cavities. Benesi–Hildebrand analysis showed that the ETR/β-CD complex adopts a 1:1 stoichiometry with association constant of K 11?=?64.8 at pH 2.0, K 11?=?105.4 at pH 6.0 and K 11?=?520.5 at pH 10.0. 相似文献
227.
IntroductionThispaperisconcernedwiththenumericalsolution ,byfinitedifferencemethod ,ofthefollowingsingularlyperturbednonlocalboundaryvalueproblem :Lu≡-εu″ +a(x)u=f(x) ( 0 <x<l) ,( 1 )L0 u≡-εu′( 0 ) +γu( 0 ) =μ0 , ( 2 )L1u≡u(l) -δu(d) =μl ( 0 <d<l) ,( 3 )whereεisasmallpositiveparameter,… 相似文献
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Musa A. Said Herbert W. Roesky Carsten Rennekamp Marius Andruh Hans‐Georg Schmidt Mathias Noltemeyer 《Angewandte Chemie (International ed. in English)》1999,38(5):661-664
A unique three‐dimensional assembly is evident in the crystal structure of the cage compound 1 : each molecule participates in the formation of eight O−H⋅⋅⋅O hydrogen bonds with neighboring molecules to form cavities with approximate dimensions of 3×3×8 Å3. In contrast, compound 2 , which contains the same framework structure, does not show this behavior in the crystal. 相似文献
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