A family of fifteen glycoclusters based on a cyclic oligo‐(1→6)‐β‐D ‐glucosamine core has been designed as potential inhibitors of the bacterial lectin LecA with various valencies (from 2 to 4) and linkers. Evaluation of their binding properties towards LecA has been performed by a combination of hemagglutination inhibition assays (HIA), enzyme‐linked lectin assays (ELLA), and isothermal titration microcalorimetry (ITC). Divalent ligands displayed dissociation constants in the sub‐micromolar range and tetravalent ligands displayed low nanomolar affinities for this lectin. The influence of the linker could also be demonstrated; aromatic moieties are the best scaffolds for binding to the lectin. The affinities observed in vitro were then correlated with molecular models to rationalize the possible binding modes of these glycoclusters with the bacterial lectin. 相似文献
The two-dimensional potential energy scan shows that the pseudo-trans conformer of 1,5-dinitrobiuret (DNB) is the most stable form of isolated molecule, while the pseudo-cis conformer is about 7.5 kJ/mol higher in energy. Thus, the structure of gaseous DNB is different from that in crystal state, where the molecules have pseudo-cis conformation. The value of enthalpy of formation of gaseous DNB (?257 ± 5 kJ/mol) is calculated from isodesmic reactions using G4 energies. Combining this value with empirically estimated enthalpy of sublimation, the enthalpy of formation of crystal DNB is predicted to be ?415 ± 15 kJ/mol. The bond dissociation enthalpies are calculated for all bonds. The energy of the weakest N–NO2 bonds is equal to 190–200 kJ/mol. Similar calculations were carried out for biuret. The gaseous biuret exists predominantly in the pseudo-trans form. The calculated enthalpy of formation of gaseous biuret agrees well with the experimental one. The correlation of calculated bond energies with corresponding bond distances and electron density is discussed for biuret and DNB. 相似文献
A new electrochemical method for the detection of cannabinoids in food products is proposed. The method is based on the voltammetry of microparticles at a paraffin‐impregnated graphite electrode. In square‐wave voltammetry, in 0.1 M KNO3 at pH 7, the responses of delta‐9‐tetrahydrocannabinol, cannabinol and cannabidiol consist of a single peak with the maximum at 0.55 V±0.01 V. This peak is ascribed to the electrooxidation of the phenol group to phenoxy radical. In microparticles of hemp and marijuana cannabinoids can be detected in pure drug as well as in the mixture with foreign insoluble powders. 相似文献
For the first time, nascent soot particles are probed by using helium‐ion microscopy (HIM). HIM is a technique that is similar to scanning electron microscopy (SEM) but it can achieve higher contrast and improved surface sensitivity, especially for carbonaceous materials. The HIM microscope yields images with a high contrast, which allows for the unambiguous recognition of smaller nascent soot particles than those observed in previous transmission electron microscopy studies. The results indicate that HIM is ideal for rapid and reliable probing of the morphology of nascent soot, with surface details visible down to approximately 5 nm, and particles as small as 2 nm are detectable. The results also show that nascent soot is structurally and chemically inhomogeneous, and even the smallest particles can have shapes that deviate from a perfect sphere. 相似文献
Human acetylcholinesterase (AChE) is a widely studied target enzyme in drug discovery for Alzheimer’s disease (AD). In this paper we report evaluation of the optimum structure and chemistry of the supporting material for a new AChE-based fluorescence sensing surface. To achieve this objective, multilayered silicon wafers with spatially controlled geometry and chemical diversity were fabricated. Specifically, silicon wafers with silicon oxide patterns (SiO2/Si wafers), platinum-coated silicon wafers with SiO2 patterns (SiO2/Pt/Ti/Si wafers), and Pt-coated wafers coated with different thicknesses of TiO2 and SiO2 (SiO2/TiO2/Pt/Ti/Si wafers) were labelled with the fluorescent conjugation agent HiLyte Fluor 555. Selection of a suitable material and the optimum pattern thickness required to maximize the fluorescence signal and maintain chemical stability was performed by confocal laser-scanning microscopy (CLSM). Results showed that the highest signal-to-background ratio was always obtained on wafers with 100 nm thick SiO2 features. Hence, these wafers were selected for covalent binding of human AChE. Batch-wise kinetic studies revealed that enzyme activity was retained after immobilization. Combined use of atomic-force microscopy and CLSM revealed that AChE was homogeneously and selectively distributed on the SiO2 microstructures at a suitable distance from the reflective surface. In the optimum design, efficient fluorescence emission was obtained from the AChE-based biosensing surface after labelling with propidium, a selective fluorescent probe of the peripheral binding site of AChE.
Figure
Micropatterned silicon wafers containing covalently bound human acetylcholinesterase. The binding and displacement of the fluorescent probe propidium (red areas) from the enzyme's peripheral binding site is visualized by scanning laser microscopy 相似文献
The research into the aqueous photocatalytic oxidation of the anti-inflammatory drug prednisolone was undertaken with P25 titanium dioxide (Evonik) and visible light-sensitive sol-gel synthesized titania-based photocatalysts containing carbon, sulphur, and iron. Possible prednisolone photocatalytic oxidation reaction pathways were proposed based on a number of oxidation by-products determined in the present study. The prednisolone adsorption properties, effects of initial prednisolone concentration, pH, usual wastewater matrix admixtures, like carbamide and sucrose, were studied. The nontoxicity of doped catalysts towards Tetrahymena thermophila, a ciliate protozoa present in the activated sludge, indicated their lower oxidative ability compared to P25, but also implied their potential application in pre-treatment of toxic hazardous materials under VIS or solar radiation before the biological degradation stage. 相似文献
We report on the time-resolved detection of the three fluoroquinolone (FQs) antibiotics ciprofloxacin (CIP), enrofloxacin (ENR) and flumequine (FLU). On addition of terbium(III) ions, the terbium(III)-FQs chelates are formed in-situ in an on-capillary derivatization reaction of a microfluidic system. The laser-induced terbium(III)-sensitized luminescence of the chelates is measured at excitation/emission wavelengths of 337/545 nm. The analytes can be separated and quantified within less than 4 min. A solid phase extraction step for analyte preconcentration can be included prior to chelation and microchip capillary electrophoresis. The analytical ranges of the calibration graphs for CIP, ENR and FLU are from 10.6 to 60.0, 10.3 to 51.0, and 11.5 to 58.8 ng mL−1, respectively, and the detection limits are 3.2, 3.1 and 3.6 ng mL−1, respectively. The precision was established at two concentration levels of each analyte and revealed relative standard deviations in the range from 3.0 to 10.2 %. The method was applied to the analysis of FQ-spiked water samples.
We report on the time-resolved detection of the three fluoroquinolone antibiotics. The analytes can be separated and quantified within less than 4 min. A solid phase extraction step for analyte preconcentration can be included prior to chelation and microchip capillary electrophoresis.
15, 16, and 17-Membered lactones based on the bis-3,4(indol-1-yl)maleimide framework were obtained using intramolecular esterification reaction starting from 3-(1-ω-carboxyalkyl-2,3-dihydroindol-1-yl)-4-(1-ω-hydroxyalkyl-2,3-dihydroindol-1-yl)-maleimides. 3,4-Dibromo-maleimide, ω-(2,3-dihydroindol-3-yl)alkanoic acids, and ω-(2,3-dihydroindol-3-yl)alkanoles were used as starting compounds. Substitution of Br for the substituted indolines followed by the intramolecular cyclization of O-silylated hydroxyl acids derivatives led to macrolactones that incorporated 4-(dihydroindol-1-yl)-3-(indol-1-yl)maleimide moieties. Indoline nuclei in these compounds were dehydrogenated by DDQ in refluxing toluene to give 15, 16 or 17-membered lactones 3-[(ω-3-carboxyalkylindol-1-yl)-4-(ω-hydroxyalkylindol-1-yl)maleimides. Quantum chemical calculations showed that the formation of macrolactones of smaller size (13-membered) corresponds to the higher Gibbs energy ΔG# and correlates with the absence of the target reaction product. 相似文献
The modification of relevant chemical properties of rhodopsin-based molecular photoswitches is presented. We show how both the substituents present and the nitrogen atom quaternization are capable to change the wavelength of absorption and the thermal stability of the photoisomer. Adjusting these properties, the molecular switches could be turned into useful compounds for solar energy storage devices. 相似文献