ABSTRACT Five multivalent β-D-GalNAc-(1→4)-β-D-Gal oligomers were selected and synthesized as probes for investigating the adhesin-receptor interactions of P. aeruginosa pili with multivalent receptors. They were synthesized by the amide coupling reactions of 8-(N-2-aminoethyl)carboxamidooctyl 4-O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-β-D-galactopyranoside (7) with EDTA dianhydride, EDTA, Kemp's triacid and adipic acid with EDC, DIC and DCC combined with HOBt as coupling reagents and by the reaction of per-O-acetylated 7 with 1,3,5-benzenetricarbonyl trichloride followed by de-O-acetylation. These resulting multivalent compounds contain flexible C9 spacer arms as linkers attached to either flexible hydrophilic moieties or rigid hydrophobic cores. 相似文献
A fluorescent probe for the sensitive and selective determination of sulfide ions is presented. It is based on the use of graphene quantum dots (GQDs) which emit strong and stable blue fluorescence even at high ionic strength. Copper(II) ions cause aggregation of the GQDs and thereby quench fluorescence. The GQDs-Cu(II) aggregates can be dissociated by adding sulfide ions, and this results in fluorescence turn on. The change of fluorescence intensity is proportional to the concentration of sulfide ions. Under optimal conditions, the increase in fluorescence intensity on addition of sulfide ions is linearly related (r2 = 0.9943) to the concentration of sulfide ions in the range from 0.20 to 20 μM, and the limit of detection is 0.10 μM (at 3 σ/s). The fluorescent probe is highly selective for sulfide ions over some potentially interfering ions. The method was successfully applied to the determination of sulfide ions in real water samples and gave recoveries between 103.0 and 113.0 %.
A graph is symmetric if its automorphism group acts transitively on the set of arcs of the graph. In this paper, we classify hexavalent symmetric graphs of order for each prime . 相似文献
The chemical oxidation polymerization of m-phenylenediamine (MPD) by ammonium persulfate (APS) at room temperature results in the formation of poly(m-phenylenediamine) (PMPD) microparticles. The subsequent treatment of such microparticles with an aqueous AgNO(3) solution produces Ag nanoparticle (AgNP)-decorated PMPD microparticles. It was found that as-formed AgNPs exhibited remarkable catalytic performance toward the reduction of hydrogen peroxide (H(2)O(2)). The enzymeless H(2)O(2) sensor constructed with such composites showed a fast amperometric response time of less than 5 s, and the corresponding linear range and detection limit were estimated to be from 0.1 to 30 mM and 4.7 μM, respectively, at a signal-to-noise ratio of 3. 相似文献
Morphology control of functional materials is generally performed by controlling the growth rates on selected orientations or faces. Here, we control particle morphology by "crystal templating": by choosing appropriate precursor crystals and reaction conditions, we demonstrate that a material with rhombohedral symmetry-namely the layered, positive electrode material, LiCoO(2)-can grow to form a quadruple-twinned crystal with overall cubic symmetry. The twinned crystals show an unusual, concaved-cuboctahedron morphology, with uniform particle sizes of 0.5-2 μm. On the basis of a range of synthetic and analytical experiments, including solid-state NMR, X-ray powder diffraction analysis and HRTEM, we propose that these twinned crystals form via selective dissolution and an ion-exchange reaction accompanied by oxidation of a parent crystal of CoO, a material with cubic symmetry. This template crystal serves to nucleate the growth of four LiCoO(2) twin crystals and to convert a highly anisotropic, layered material into a pseudo-3-dimensional, isotropic material. 相似文献
In this Communication, we report water-soluble nano-C(60) in the first use as an effective fluorescent sensing platform for the highly sensitive and selective detection of Ag(+). The general concept used in this approach is based on a fluorescently labeled single-stranded DNA (ssDNA) probe that adsorbs on nano-C(60), leading to substantial dye fluorescence quenching; however, in the presence of Ag(+), C-Ag(+)-C coordination induces the probe to fold into a hairpin structure, which does not adsorb on nano-C(60) and thus retains the dye fluorescence. This sensing system exhibits a detection limit as low as 1 nM and has a high selectivity against other metal ions. Finally and most importantly, we demonstrate its performance in real sample analysis. 相似文献