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981.
Sara Tavakkolifard Dr. Kohei Sekine Lisa Reichert Mina Ebrahimi Ketevan Museridz Elena Michel Dr. Frank Rominger Rasool Babaahmadi Prof. Alireza Ariafard Prof. Brian F. Yates Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(52):12180-12186
Precise control of the selectivity in organic synthesis is important to access the desired molecules. We demonstrate a regiospecific annulation of unsymmetrically substituted 1,2-di(arylethynyl)benzene derivatives for a geometry-controlled synthesis of linear bispentalenes, which is one of the promising structures for material science. A gold-catalyzed annulation of unsymmetrically substituted 1,2-di(arylethynyl)benzene could produce two isomeric pentalenes, but both electronic and steric effects on the aromatics at the terminal position of the alkyne prove to be crucial for the selectivity; especially a regiospecific annulation was achieved with sterically blocked substituents; namely, 2,4,6-trimetyl benzene or 2,4-dimethyl benzene. This approach enables the geometrically controlled synthesis of linear bispentalenes from 1,2,4,5-tetraethynylbenzene or 2,3,6,7-tetraethynylnaphthalene. Moreover, the annulation of a series of tetraynes with a different substitution pattern regioselectively provided the bispentalene scaffolds. A computational study revealed that this is the result of a kinetic control induced by the bulky NHC ligands. 相似文献
982.
983.
984.
Maxwell D. Cummings Jimmy Lindberg Tse‐I Lin Herman de Kock Oliver Lenz Elisabet Lilja Sara Felländer Vera Baraznenok Susanne Nyström Magnus Nilsson Lotta Vrang Michael Edlund Åsa Rosenquist Bertil Samuelsson Pierre Raboisson Kenneth Simmen 《Angewandte Chemie (International ed. in English)》2010,49(19):3250-3250
985.
986.
A highly accurate method for simulating surfactant-covered droplets in two-dimensional Stokes flow with solid boundaries is presented. The method handles both periodic channel flows of arbitrary shape and stationary solid constrictions. A boundary integral method together with a special quadrature scheme is applied to solve the Stokes equations to high accuracy, also for closely interacting droplets. The problem is considered in a periodic setting and Ewald decompositions for the Stokeslet and stresslet are derived. Computations are accelerated using the spectral Ewald method. The time evolution is handled with a fourth-order, adaptive, implicit-explicit time-stepping scheme. The numerical method is tested through several convergence studies and other challenging examples and is shown to handle drops in close proximity both to other drops and solid objects to high accuracy. 相似文献
987.
Surya Subianto Sara Cavaliere Deborah J. Jones Jacques Rozière 《Journal of polymer science. Part A, Polymer chemistry》2013,51(1):118-128
The effect of the side‐chain length (short side chain and long side chain, SSC and LSC, respectively) of perfluorosulfonic acid (PFSA) ionomers on the properties of nanofibers obtained by electrospinning ionomer dispersions in high dielectric constant liquids has been investigated with a view to obtaining electrospun webs as components of fuel cell membranes. Ranges of experimental conditions for electrospinning LSC and SSC PFSAs have been explored, with a scoping of solvents, carrier polymer and PFSA ionomer concentrations, and carrier polymer molecular weight. Under optimal conditions, the electrospun mats derived from SSC and from LSC PFSA show distinct fiber dimensions that arise from the different chain lengths of the respective ionomers. Enhanced interchain interactions in SSC PFSA with low equivalent weight compared to LSC PFSA result in a considerably lower average fiber diameter and a markedly narrower fiber size distribution. The proton conductivity of nanofiber mats of SSC and LSC PFSA with equivalent weights of 830 and 900 g mol?1, respectively, are 102 and 58 mS cm?1 at 80°C and 95% relative humidity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
988.
Maxwell D. Cummings Jimmy Lindberg Tse‐I Lin Herman de Kock Oliver Lenz Elisabet Lilja Sara Felländer Vera Baraznenok Susanne Nyström Magnus Nilsson Lotta Vrang Michael Edlund Åsa Rosenquist Bertil Samuelsson Pierre Raboisson Kenneth Simmen 《Angewandte Chemie (International ed. in English)》2010,49(9):1510-1510
989.
The partition coefficients for several solutes (five nitrophenylated-monosaccharides and four proteins) were experimentally determined, at 23 °C, in three different tie-lines of two polymer–salt aqueous two-phase systems (ATPS): UCON-K2HPO4 and UCON-NaH2PO4. These partition coefficients together with others obtained from the literature for five dinitrophenylated-amino acids were used to investigate the suitability of the Collander equation to correlate partition coefficients in polymer–salt ATPS. This equation was first proposed to describe the linear correlation between partition coefficients of solutes in different water–organic solvent systems. More recently, it was proved that partition coefficients for several biomolecules in polymer–polymer ATPS can also be correlated with this equation. In this work, several correlations were tested: partition coefficients obtained for different tie-lines within the same system and also partition coefficients obtained from different systems. In both cases, a linear relation was observed, despite a less satisfactory correlation was found when different ATPS were compared. Overall, it was demonstrated that the Collander equation can be used to satisfactorily correlate solute partitioning in the studied polymer–salt ATPS. 相似文献
990.
Stefano Salmaso Alessandra Semenzato Sara Bersani Francesca Mastrotto Anna Scomparin Paolo Caliceti 《European Polymer Journal》2008,44(5):1378-1389
A two step protocol has been set up to selectively conjugate PEG to buried amino acids of proteins. The process involves site-specific glycation followed by PEGylation of the oxidized glycosides. Aimed at glycating the cysteine groups of proteins, two maleimide-glycosylic linkers have been synthesised: galactosyl-glucono-CO–NH–(CH2)12–NH–CO–(CH2)2-maleimide and maltosyl-glucono-CO–NH–(CH2)12–NH–CO–(CH2)2-maleimide. The linkers were extensively characterized by 1H NMR, FT-IR, ESI–TOF mass spectrometry and colorimetric assays. Complete conjugation of the activated linkers to Cys34 of human serum albumin was obtained in about 2 h. The selective oxidation of the galactosyl and maltosyl moieties by periodate treatment yielded two and three available aldehyde groups, respectively. The PEG-hydrazide conjugation to the aldehyde groups was found to be 100% in about 40 h, whereas less than 30% protein modification was obtained by direct conjugation of commercial PEG-maleimide to Cys34. The pH dependent PEG-glycosyl hydrazone bond hydrolysis at various pH values was verified. PEG release was faster under mild acidic and basic conditions than at neutral pH. Furthermore, the maltosyl derivatives, by virtue of the higher number of coupled PEG chains, showed a slower protein release as compared to the galactosyl counterpart, indicating that the choice of the glycosylic linker allows for control of protein release kinetics. 相似文献