Syntheses of a new type of chiral phosphines from glucose

Methyl 3-deoxy-3-(diphenylphosphino)-4,6-O-benzylidene-α-D-altropyranoside (1) and methyl 2-deoxy-2-(diphenylphosphino)-4,6-O-benzylidene-α-D-altropyranoside (2) were prepared from methyl 2,3-anhydro-4,6-O-benzylidene-O-D-mannopyranoside and methyl 2,3-anhydro-4,6-O-benzyl-idene-α-D-allopyranoside,respectively,via regioselective and stcreospecific ring-opening reactions in high yields.Compounds 1 and 2 were oxidized to give the corresponding phosphine oxides (3 and 4).     

Preparation and adsorption properties of glucose molecularly imprinted polymers in hydrous solution for effective determination of glucose in fruits by MISPE–HPLC

In this paper, a kind of surface molecular imprinting polymers in hydrous solution, with glucose selectively recognition, was successfully synthesized by surface molecular imprinting method, using glucose (Glu) as template molecule, acrylamide as functional monomers, N,N′-methylenebisacrylamide as the cross-linking agent, ammonium peroxydisulfate as the initiator, activated silica gel (SiO₂@NH₂) as support particles. The influences of cross-linker, initiator as well as support particles amount on the adsorption capacity of Glu-MIPs were performed by single-factor experiments. The optimum conditions were 100 mg of cross-linker, 25 mg of initiator and 1 g of SiO₂@NH₂. The adsorption and thermodynamics research revealed that the adsorption of MIPs was fitted to Langmuir, maximum imprinting factor of 2.49 and maximum absorption capacity of 50.06 mg/g. Furthermore, a procedure of extraction of glucose from real fruits samples using the Glu-MIPs as solid-phase extraction adsorbent was developed to apply in analytical techniques.     

Thermodynamic study of the influence of polyols and glucose on the thermal stability of holo-bovine α-lactalbumin

Thermal stability of bovine α-lactalbumin in buffer and dilute aqueous solutions of erythritol, xylitol, sorbitol, inositol and glucose was evaluated by fluorescence spectroscopy and circular dichroism. Results show that at the selected conditions, the transition is reversible and is well described by a two-state model. At low concentration the cosolutes do not show a structure stabilizing effect, and some of them even destabilize the protein. At higher concentration, all of them stabilize the native protein conformation; however, the extent of stabilization is lower than the effect shown with other proteins, presumably due to the lactalbumin incomplete unfolding.     

Synthesis of N-glycyl-β-glycopyranosyl amines,derivatives of natural oligosaccharides — glucose analogs of Lex antigen

Treatment of the natural tri-, tetra-, and pentasaccharides, β-d-Galp-(1→4)-[α-l-Fucp-(1→3)]-d-Glcp, α-l-Fucp-(1→2)-β-d-Galp-(1→4)-[α-l-Fucp-(1→3)]-d-Glcp, and α-l-Fucp-(1→2)-[α-d-GalNAcp-(1→3)]-β-d-Galp-(1→4)-[α-l-Fucp-(1→3)]-d-Glcp, which are glucose analogs of Le^x, with ammonium carbamate in aqueous methanol gave the corresponding β-glycopyranosyl amines. After their N-acylation with N-Z-glycine N-hydroxysuccinimidyl ester (Z is benzyloxycarbonyl) with subsequent hydrogenolytic removal of Z-group, corresponding N-glycyl-β-glycopyranosyl amines were obtained in yields up to 70%.     

Preparation of an ultrafiltration membrane from the copolymer of acrylonitrile–glycidylmethacrylate utilized for immobilization of glucose oxidase

Ultrafiltration membrane has been prepared from the copolymer of acrylonitrile–glycidylmethacrylate and the porosity of the membrane was studied. The asymmetric structure was proved by scanning electron microscopy. The basic characteristics of the membrane were measured – water permeability, water content, membrane selectivity, etc. The membrane obtained was used as a carrier for immobilization of glucose oxidase. The immobilization was carried out covalently by two methods: direct bonding of the enzyme and indirectly by a spacer (hexamethylenediamine) and cross-linking agent (glutar aldehyde). The amount of bound protein and relative activity of the immobilized glucose oxidase were determined. Temperature optimum, pH optimum and storage stability of the immobilized glucose oxidase were determined. It was proved that glucose oxidase immobilized by the direct method shows better characteristics compared with the indirect method.     

Azetidine iminosugars from the cyclization of 3,5-di-O-triflates of α-furanosides and of 2,4-di-O-triflates of β-pyranosides derived from glucose

Primary amines with either 3,5-di-O-ditriflates of α-furanosides or 2,4-di-O-triflates of β-pyranosides form bicyclic azetidines in high yield.     

Macrokinetics of processes in glucose oxidase—peroxidase bienzyme systems when assaying glucose by the H2O2 reduction current: Effect of the enzyme ratio on the steady-state potential and H2O2 reduction current in glucose solutions of different concentrations

The effect of the enzyme ratio on the steady-state potential and H₂O₂ reduction current at a bienzyme glucose oxidase-peroxidase electrode in glucose solutions of different concentrations is studied. The derived equations adequately describe the experimental data and allow one to estimate characteristics of bienzyme electrodes in the linear domain of the current variation with the glucose concentration and the system’s sensitivity     

Synthesis of ZnO nanobundles via Sol–Gel route and application to glucose biosensor

ZnO nanobundles were fabricated by Sol–Gel route. The as-prepared ZnO nanobundles were characterized by XRD, FE-SEM, TEM and PL. ZnO nanobundles structure are composed of many nanorods of about 80 nm in diameter and 0.6 μm in length. It showed weaker UV emission and stronger green emission. A glucose biosensor was constructed using these ZnO nanobundles as supporting materials for glucose oxidase (GO_X) loading by chitosan-assisted cross-linking technique. The biosensor exhibits a high affinity, high sensitivity, and fast response for glucose detection. These results demonstrate that zinc oxide nanostructures have potential applications in biosensors.     

Sol–gel synthesis and XPS study of vanadium pentoxide xerogels intercalated with glucose

Vanadium–glucose xerogels (C₆H₁₂O₆)_xV₂O₅·nH₂O with different amounts of glucose (x = 0; 0.3 and 0.5) have been synthesized by sol–gel method. The scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods were used to investigate the morphology and composition of obtained xerogels. SEM results show that after intercalation of the glucose molecules the surface structure became more spongy and porously. XPS analysis show that the increasing of glucose concentration in the compounds the reduction ratio of vanadium ions increases. The oxygen ions in the synthesized vanadium–glucose xerogels are bounded to the vanadium ions, carbon ions are involved in a chemical bounding in the hydroxyl group. The determined carbon ions chemical bonds are characteristic for glucose (C–C, CH–OH and C–O bonds). Some of the oxygen ions in the pure vanadium pentoxide xerogels are bonded in water molecules. This fact and the absence of the oxygen component which corresponds to the water in glucose-vanadium xerogels indicate that glucose molecules displaced structural water in vanadium hydrate and are intercalated between the vanadium–oxygen layers.     

A novel sensitive non-enzymatic glucose sensor

Cu nanoclusters were electrochemically deposited on the film of a Nafion-solubilized multi-wall carbon nanotubes (CNTs) modified glassy carbon electrode (CNTs-GCE), which fabricated a Cu-CNTs composite sensor (Cu-CNTs-GCE) to detect glucose with non-enzyme. The linear range is 7.0×10-7 to 3.5×10-3 mol/L with a high sensitivity of 17.76μA/(mmol L), with a low detection limit 2.1×10-7 mol/L, fast response time (within 5 s), good reproducibility and stability.     

Carbohydrate hydration: heavy water complexes of α and β anomers of glucose, galactose, fucose and xylose

The singly and doubly hydrated complexes of the α and β anomers of a systematically varied set of monosaccharides, O-phenyl D-gluco-, D-galacto-, L-fuco- and D-xylopyranoside, have been generated in a cold molecular beam and probed through infrared-ultraviolet double resonance ion-dip (IRID) spectroscopy coupled with quantum mechanical calculations. A new 'twist' has been introduced by isotopic substitution, replacing H(2)O by D(2)O to separate the carbohydrate (OH) and hydrate (OD) vibrational signatures and also to relieve spectral congestion. The new spectroscopic and computational results have exposed subtle aspects of the intermolecular interactions which influence the finer details of their preferred structures, including the competing controls exerted by co-operative hydrogen bonding, bi-furcated and OH-π hydrogen bonding, stereoelectronic changes associated with the anomeric effect, and dispersion interactions. They also reassert the operation of general 'working rules' governing conformational change and regioselectivity in both singly and doubly hydrated monosaccharides.     

Direct electrochemistry of glucose oxidase on a graphite nanosheet–Nafion composite film modified electrode

The direct electrochemistry of glucose oxidase (GOD) immobilized in a modified electrode based on a composite film of exfoliated graphite nanosheets (GNSs) and Nafion has been investigated for the first time. Direct electron communication between GOD and the electrode was achieved with a fast electron transfer rate (12.6 s^?1). In addition, the bioactivity of GOD was retained after immobilization in the composite film and glucose could be determined based on the decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen. The resulting biosensor exhibited higher sensitivity (3.4 μA mM^?1). Considering much lower cost of GNSs and ready preparation from graphite, the GNSs-based modified electrode described here is superior to the carbon nanotubes (CNTs)-based modified electrodes and should have wide applications in third-generation biosensors, bioelectronics and electrocatalysis.     

Predominating stable adsorption and direct electrochemistry of glucose oxidase on carbon nanotubes by oxygen-containing groups

Stable adsorption and direct electrochemistry of glucose oxidase (GOx) occurred on nitric acid (HNO3)-treated multi-walled carbon nanotubes (MWNTs) instead of as-received MWNTs, demonstrating the critical roles of oxygen-containing groups in stableadsorption and direct electrochemistry of GOx on carbon nanotubes (CNTs).     

Electrodeposition of PtCo alloy nanoparticles on inclusion complex film of functionalized cyclodextrin–ionic liquid and their application in glucose sensing

Platinum–cobalt (PtCo) alloy nanoparticles (NPs) are successfully fabricated by ultrasonic-electrodeposition method, using an inclusion complex (IC) film of functionalized cyclodextrin (CD)–ionic liquid (IL) as support. The morphology and composition of the PtCo alloy NPs are characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. It is found that they are well-dispersed on the CD–IL surface and exhibit many unique features. The resulting modified glassy carbon electrode shows excellent catalytic activity for glucose oxidation. Under the physiological condition, the oxidation current of glucose is linear to its concentration up to 20 mM with sensitivity of 13.7 μA mM^?1 cm^?2. In addition, the interference from the oxidation of ascorbic acid and uric acid could be effectively avoided. Therefore, it is promising as a nonenzymatic glucose sensor.     

First application of mass spectrometry and gas chromatography in investigation of α-cellulose hydrolysates: the influence of climate changes on glucose molecules in pine tree-rings

We present the first results of the quantitative and qualitative gas chromatographic and isotope ratio mass spectrometric analysis of monosaccharides derived from acid hydrolysis of α-cellulose extracted from annual pine tree-rings. The conifers investigated in this study grew in the Niepolomice Forest in Poland, and the annual rings covered the time span from 1940 to 2000 AD. The main components of the α-cellulose samples were two saccharides: glucose and mannose. The amount of glucose in the annual rings varied between 17 and 44%. The δ(13)C of glucose was found to be less negative than that of α-cellulose and the δ(18)O values in glucose were less positive than those in α-cellulose. The content of monosaccharides in the α-cellulose samples has an influence on the isotope fractionation factors. The values of the carbon isotope fractionation factor increase with an increase in the monosaccharides concentration in α-cellulose, while the values of the oxygen isotope fractionation factor decrease with an increase in monosaccharides concentration in α-cellulose. The challenge is to establish, with respect to climate changes and environmental conditions, the significance of the interannual variations in the observed monosaccharide concentration.     

Electropolymerization of carboxymethyl-β-cyclodextrin based on co-electrodeposition gold nanoparticles electrode: electrocatalysis and nonenzymatic glucose sensing

A facile strategy is developed to fabricate an Au-CMCD/PCMCD electrode with high efficiency, universal, and selectivity electrocatalysis through electro-depositing carboxymethyl-β-cyclodextrins with gold nanoparticles (Au-CMCD) followed by employing electro-polymerization carboxymethyl-β-cyclodextrin (PCMCD). The chemical structure, microstructure, electrochemical activity, and electrocatalytic properties of Au-CMCD/PCMCD electrode are investigated. Due to the synergistic effect of the PCMCD and Au-CMCD layers, the as-prepared electrode exhibits an outstanding enhancement of universal electrocatalytic activity to eight kinds of crucial biomolecules and drugs, such as chloramphenicol, thymine, and glucose. Then, as a target analyte, glucose is used to investigate the sensing performances of Au-CMCD/PCMCD electrode. The amperometric detection of glucose shows a wide linear range expanding to 0.001～110 mM with a low detection limit of 0.99 μM. More importantly, the absorption effect of PCMCD is stronger to glucose than other interfering species, which is favorable to avoid the influence of possible interfering substances. Furthermore, the glucose sensors reveal good stability and repeatability.     

FT-IR microscopy characterization of sol–gel layers prior and after glucose oxidase immobilization for biosensing applications

Micro-Attenuated Total Reflection (ATR) Fourier Transform Infrared spectroscopy was used to investigate sol–gel layers for biosensing applications prior and after glucose oxidase (GOD) immobilization. The changes occurring in sol–gel infrared spectrum after GOD immobilization were clearly evidenced confirming the retaining of the enzyme activity. Moreover, micro-ATR experimental technique allowed us to investigate the spatial distribution of enzyme concentration. The non-destructive nature of our approach also enabled to monitor the time stability of sol–gel layers and of embedded GOD. The temporal evolution of some peaks in infrared spectra of these sol–gel layers was compared with absorption and steady-state fluorescence measurements. The results reported here confirm that micro-ATR infrared spectroscopy can be usefully employed for a non- or minimally invasive detailed characterization of supports for enzyme immobilization.