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1.
2.
Sherif El-Basil Gani Jashari Jan V. Knop Nenad Trinajstić 《Monatshefte für Chemie / Chemical Monthly》1984,115(11):1299-1312
The reduced graph model, when used in conjunction with the search trees method, provides a novel combinatorial procedure for the enumeration and generation ofKekulé structures. The procedure is suited for large benzenoid hydrocarbons consisting of cata- and thin peri-condensed parts.
Zur Anwendung des Reduced Graph Model im Zusammenhang mit Search Trees zur Ermittlung der Anzahl möglicherKekulé-Strukturen
Zusammenfassung Das Modell erlaubt mit der im Titel genannten Kombination eine neuartige Methode zur Ermittlung und Generierung vonKekulé-Strukturen. Das Verfahren ist für große benzoide Kohlenwasserstoffe geeignet, die aus cata- und (dünnen) peri-kondensierten Teilstrukturen bestehen.相似文献
3.
Sherif El-Basil 《Theoretical chemistry accounts》1986,70(1):53-65
Clar structures recently used as basis-set to compute resonance energies [9] are identified as maximal independent sets of benzenoid hydrocarbons colored in a special way. Binomial properties of such objects are induced for several catafusenes and perifusenes (Eqs. 2–31). Novel polynomials, called Clar polynomials, are given for perifusens in terms of units of catafusenes which allow display and enumeration of the populations of their Clar structures. The work is particularly pertinent to that of [8] and [9].This paper is dedicated to Professor Eric Clar; the Doyen of aromatic chemistry. 相似文献
4.
Ahmed Abd El-Fattah Mohamad Nageeb Hassan Ahmad Rashad Mona Marei Sherif Kandil 《International Journal of Polymer Analysis and Characterization》2020,25(5):362-373
Abstract An injectable composite hydrogel composed of polyvinyl alcohol (PVA) and bioactive glass (BG) particles were synthesized by a physical crosslinking approach. The morphology, mechanical properties, and viscoelasticity of the PVA/BG composite hydrogel were characterized. Scanning electronic microscopy (SEM) showed uniform and homogeneous distribution of BG particles throughout the composite hydrogel. The incorporation of 2.5?wt% of BG particles in the composite hydrogel formulations, enhanced the static compressive strength and static elastic modulus by 325% and 150%, respectively. The storage molds (G′) was greater than the loss modules (G′′) at all the frequency range studied, which revealed a self-standing elastic composite hydrogel with a smooth injectability. The PVA/BG composite hydrogel was also implanted subcutaneously in the dorsal region of adult male rats. After 4?weeks of implantation, no inflammatory cells were seen within and around the implant, which indicated that the composite hydrogel was biocompatible. The properties of the synthesized injectable PVA/BG composite hydrogel demonstrate its capability toward bone regeneration. 相似文献
5.
Sherif El-Basil 《International journal of quantum chemistry》1982,21(5):779-792
Kekulé structures of 10 nonlinear acenes comprising 83 graphs are studied through the use of connectivities [M. Randi?, J. Am. Chem. Soc. 97 , 6609 (1975)] of their corresponding submolecules [H. Joela, Theor. Chim. Acta 39 , 241 (1975)]. In certain rare cases states were identified to have identical branching indices but different Kekulé indices [A. Graovac, I. Gutman, M. Randi?, and N. Trinajsti?, J. Am. Chem. Soc. 95 , 6267 (1973)]. Such states are termed pseudodegenerate states. A method is described to forecast and another to remedy such situations. The method emphasizes the relation between VB (resonance) and MO theories using graph-theoretical concepts. 相似文献
6.
Sherif El-Basil 《International journal of quantum chemistry》1982,21(5):793-797
Molecular connectivities of submolecules [H. Joela, Theor. Chim. Acta 39 , 241 (1975)] corresponding to Kekulé structures of nine nonalternate hydrocarbons and four nonbenzenoid hydrocarbons containing four-membered rings are correlated with their Kekulé indices. In the latter class of compounds it was observed that the corresponding submolecules contain cut vertices and bridges in contrast to submolecules of benzenoid hydrocarbons which are devoid of such bridges. It was observed, furthermore, that the branching index goes up with the number of bridges in the submolecule. The results present an application to the abstract relation [D. Cvetkovi?, I. Gutman, and N. Trinajsti?, J. Chem. Phys. 61 , 2700 (1974)] between resonance and MO theories. 相似文献
7.
Wagnat W. Wardakhan Hatem M. Gaber Salama A. Ouf Sherif M. Sherif 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):601-618
Abstract Heterocyclic enamines1 reacted with ethyl acetoacetate to afford the corresponding amide derivatives2. Treatment of2 with carbon disulphide yielded the dipotassium salts3which reacted in-situ with a variety of α -haloketones to give the respective substituted thiophenes5,8, and13. The reactivity of the latter products towards various chemical reagents was studied to yield their fused thiophene derivatives7,10,12, and14, respectively. Some representative compounds were tested for antimicrobial activity. 相似文献
8.
Sherif O. Kolade Josephat U. Izunobi Eric C. Hosten Idris A. Olasupo Adeniyi S. Ogunlaja Oluwole B. Familoni 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(8):810-820
The title compound, 10‐iodo‐1,2‐dihydroisoquinolino[2,1‐b][1,2,4]benzothiadiazine 12,12‐dioxide, C15H11IN2O2S ( 8 ), was synthesized via the metal‐free intramolecular N‐iodosuccinimide (NIS)‐mediated radical oxidative sp3‐C—H aminative cyclization of 2‐(2′‐aminobenzenesulfonyl)‐1,3,4‐trihydroisoquinoline, C15H16N2O2S ( 7 ). The amino adduct 7 was prepared via a two‐step reaction, starting from the condensation of 2‐nitrobenzenesulfonyl chloride ( 4 ) with 1,2,3,4‐tetrahydroisoquinoline ( 5 ), to afford 2‐(2′‐nitrobenzenesulfonyl)‐1,3,4‐trihydroisoquinoline, C15H14N2O4S ( 6 ), in 82% yield. The catalytic hydrogenation of 6 with hydrogen gas, in the presence of 10% palladium‐on‐charcoal catalyst, furnished 7 . Products 6 – 8 were characterized by their melting points, IR and NMR (1H and 13C) spectroscopy, and single‐crystal X‐ray diffraction. The three compounds crystallized in the monoclinic space group, with 7 exhibiting classical intramolecular hydrogen bonds of 2.16 and 2.26 Å. All three crystal structures exhibit centrosymmetric pairs of intermolecular C—H…π(ring) and/or π–π stacking interactions. The docking studies of molecules 6 , 7 and 8 with deoxyribonucleic acid (PDB id: 1ZEW ) revealed minor‐groove binding behaviours without intercalation, with 7 presenting the most favourable global energy of the three molecules. Nonetheless, molecule 8 interacted strongly with the DNA macromolecule, with an attractive van der Waals energy of ?15.53 kcal mol?1. 相似文献
9.
El-Safty SA Ismail AA Matsunaga H Mizukami F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(33):9245-9255
Appropriate design of nanosensors for optically selective, sensitive sensing systems is needed for naked-eye detection of pollutants for environmental cleanup of toxic heavy-metal ions. Mesostructured materials with two- or three-dimensional (2D or 3D) geometries and large particle morphologies show promise as probe carriers, and can therefore be used to reproducibly fabricate uniformly packed nanosensors. This is the first report on the effects of significant key properties of the mesostructured carriers, such as morphology, geometry, and pore shape, on the functionality of optical nanosensor designs. Such mesostructured sensors with superior physical characteristics can be used as components in sensing systems with excellent stability and sensitivity, and with rapid detection response. The nanosensor design can enhance the selectivity even at low concentrations of the pollutant target ions (nanomolar level). Among the nanosensors developed here, the large pore-surface grains of highly ordered 3D monoliths (HOM) exhibited a high adsorption capability of the Pyrogallol Red probe and high accessibility to analyte ion transport, leading to possible naked-eye detection of Sb(III) ions at concentrations as low as 10(-9) mol dm(-3) and at a wide detection range of 0.5 ppb to 3 ppm. A key finding in our study was that our mesostructured nanosensor designs retained highly efficient sensitivity without a significant increase in kinetic hindrance, despite the slight decrease of the specific activity of the electron acceptor/donor strength of the probe functional group after several regeneration/reuse cycles. The results, in general, indicate that large-scale reversibility of optical nanosensors is feasible in such metal-ion sensing systems. 相似文献
10.
Kedar N. Baryal Sherif Ramadan Guowei Su Changxin Huo Yuetao Zhao Jian Liu Linda C. Hsieh-Wilson Xuefei Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202211985
Heparan sulfate (HS) has multifaceted biological activities. To date, no libraries of HS oligosaccharides bearing systematically varied sulfation structures are available owing to the challenges in synthesizing a large number of HS oligosaccharides. To overcome the obstacles and expedite the synthesis, a divergent approach was designed, where 64 HS tetrasaccharides covering all possible structures of 2-O-, 6-O- and N-sulfation with the glucosamine-glucuronic acid-glucosamine-iduronic acid backbone were successfully produced from a single strategically protected tetrasaccharide intermediate. This extensive library helped identify the structural requirements for HS sequences to have strong fibroblast growth factor-2 binding but a weak affinity for platelet factor-4. Such a strategy to separate out these two interactions could lead to new HS-based potential therapeutics without the dangerous adverse effect of heparin-induced thrombocytopenia. 相似文献