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Different Spacers (different + spacer)

Distribution by Scientific Domains
Chemistry75%

Terms modified by Different Spacers

  • different spacer length
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    Selected Abstracts

    Fluorescent polymer particles by emulsion and miniemulsion polymerization

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2003
    Frédéric Tronc
    Abstract We describe the synthesis and characterization of latex particles labeled with a brightly fluorescent yellow dye (HY) based on the benzothioxanthene ring structure. Three dye derivatives were synthesized with different spacers connecting the HY nucleus to a methacrylate group. For one of the dyes (HY2CMA, rA), we show that the reactivity ratios with styrene (rA = 0.71, rB = 0.25) and butyl methacrylate (rA = 0.87, rB = 0.14) should lead to random dye incorporation if the amount of dye in the feed is small. Seeded emulsion polymerization fails to lead to significant dye incorporation unless large amounts of nonionic surfactant are present. In contrast, miniemulsion polymerization worked well to yield latex particles of polystyrene, poly(butyl methacrylate), and poly(methyl methacrylate) with high monomer conversion and essentially quantitative dye incorporation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 766,778, 2003 [source]

    Synthesis of Imidazole Derivatives with Antimycobacterial Activity

    ARCHIV DER PHARMAZIE, Issue 1 2010
    Pedro O. Miranda
    Abstract 4-Substituted 1-(p -methoxybenzyl)imidazoles were designed and synthesized in order to mimic parts of the structure of highly potent antimycobacterial 6-aryl-9-(p -methoxybenzyl)purines. 4-Haloimidazoles were subjected to Pd-catalyzed cross-coupling in order to introduce a (hetero)aryl group, or they were converted to Grignard reagents and reacted with (hetero)arylaldehydes. Further transformations of the adducts gave a variety of potential antimycobacterials with different "spacers" between the imidazole and (hetero)aryl group. The adduct from furfural was rearranged to a cyclopentenone derivative when treated with methanol under acidic conditions. Several target compounds exhibited antimycobacterial activity in vitro (IC90 13 ,g/mL for the best inhibitors), but they were not as active as the most potent purines and pyrimidines synthesized before. [source]

    Gold Manno -Glyconanoparticles: Multivalent Systems to Block HIV-1 gp120 Binding to the Lectin DC-SIGN,

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 38 2009
    Olga Martínez-Ávila Dr.
    Abstract The HIV envelope glycoprotein gp120 takes advantage of the high-mannose clusters on its surface to target the C-type lectin dendritic cell-specific intracellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) on dendritic cells. Mimicking the cluster presentation of oligomannosides on the virus surface is a strategy for designing carbohydrate-based antiviral agents. Bio-inspired by the cluster presentation of gp120, we have designed and prepared a small library of multivalent water-soluble gold glyconanoparticles (manno- GNPs) presenting truncated (oligo)mannosides of the high-mannose undecasaccharide Man9GlcNAc2 and have tested them as inhibitors of DC-SIGN binding to gp120. These glyconanoparticles are ligands for DC-SIGN, which also interacts in the early steps of infection with a large number of pathogens through specific recognition of associated glycans. (Oligo)mannosides endowed with different spacers ending in thiol groups, which enable attachment of the glycoconjugates to the gold surface, have been prepared. manno- GNPs with different spacers and variable density of mannose (oligo)saccharides have been obtained and characterized. Surface plasmon resonance (SPR) experiments with selected manno -GNPs have been performed to study their inhibition potency towards DC-SIGN binding to gp120. The tested manno -GNPs completely inhibit the binding from the micro- to the nanomolar range, while the corresponding monovalent mannosides require millimolar concentrations. manno- GNPs containing the disaccharide Man,1-2Man, are the best inhibitors, showing more than 20,000-fold increased activity (100,% inhibition at 115,nM) compared to the corresponding monomeric disaccharide (100,% inhibition at 2.2,mM). Furthermore, increasing the density of dimannoside on the gold platform from 50 to 100,% does not improve the level of inhibition. [source]

    Synthesis and Photoinduced Electron-Transfer Properties of Phthalocyanine,[60]Fullerene Conjugates

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2008
    Maurizio Quintiliani Dr.
    Abstract A series of three novel ZnPc,C60 conjugates (Pc=phthalocyanine) 1,a,c bearing different spacers (single, double, and triple bond) between the two electroactive moieties was synthesized and compared to that of ZnPc,C60 conjugate 2, in which the two electroactive moieties are linked directly. The synthetic strategy, towards the preparation of 1,a,c, involved palladium-catalyzed cross-coupling reactions over a monoiodophthalocyanine precursor 4 to introduce the corresponding spacer, and subsequent dipolar cycloaddition reaction to C60. Detailed photophysical investigations of 1,a,c and 2 prompted an intramolecular electron transfer that evolves from the photoexcited ZnPc to the electron-accepting C60. In particular, with the help of femtosecond laser photolysis charge separation was indeed confirmed as the major deactivation channel. Complementary time-dependent density functional calculations supported the spectral assignment, namely, the spectral identity of the ZnPc.+ radical cation and the C60., radical anion as seen in the differential absorption spectra. The lifetimes of the correspondingly formed radical ion-pair states depend markedly on the solvent polarity: they increase as polarity decreases. Similarly, although to a lesser extent, the nature of the linker impacts the lifetime of the radical ion-pair states. In general, the lifetimes of these states tend to be shortest in the system that lacks any spacer at all (2), whereas the longest lifetimes were found in the system that carries the triple-bond spacer (1,a). [source]