Small-sized albumin gel microspheres, MSs, containing 5-fluorouracil (5FU) with targeting moieties on their surfaces (average diameter: 1.5 μm) were prepared by the glutaraldehyde crosslinking method and suspension technique. Since galactose is known to interact specifically with the asialoglycoprotein receptor on hepato-cyte, the galactose residues were introduced on the surface of MSs as the targeting moieties for hepatoma through polyethylene glycol (PEG) spacers. PEG spacers were employed to depress the immu-nogenicity of albumin, to keep the mobility of the galactose residues, and to heighten the distributive stability of the MSs in aqueous solution. It was confirmed by ESC A analysis that the PEG chains were introduced onto the surfaces of MSs. The amount of galactose residues introduced to MS were estimated to be 0.013 wt%. The intra-MSs aggregation was observed by the addition of Ricinus Communis Agglutinin I (RCA120) into the MS suspension, and then the aggregation of MSs was dissociated by addition of free lactose. Moreover, by incubation of the MSs with human hepatoma HLE cells, the phenomena of MS's specific binding onto HLE cell surfaces and phagocytosis of MSs by HLE cells were observed. These results suggested that the galactose residues on the surface of MSs were recognized with the galactose receptors on hepatoma cell surfaces. The release rate of 5FU from MSs was investigated in vitro in physiological saline at 37OC. About 90% of encapsulated 5FU were found to be released from MSs through incubation for 8 h. 相似文献
A bienzyme biosensor in which the enzymes β‐galactosidase (β‐Gal), fructose dehydrogenase (FDH), and the mediator tetrathiafulvalene (TTF) were coimmobilized by cross‐linking with glutaraldehyde atop a 3‐mercaptopropionic acid (MPA) self‐assembled monolayer on a gold disk electrode, is reported. The working conditions selected were Eapp=+0.10 V and (25±1) °C. The useful lifetime of one single TTF‐β‐Gal‐FDH‐MPA‐AuE was surprisingly long, 81 days. A linear calibration plot was obtained for lactulose over the 3.0×10?5–1.0×10?3 mol L?1 concentration range, with a limit of detection of 9.6×10?6 mol L?1. The effect of potential interferents (lactose, glucose, galactose, sucrose, and ascorbic acid) on the biosensor response was evaluated. The behavior of the SAM‐based biosensor in flow‐injection systems in connection with amperometric detection was tested. The analytical usefulness of the biosensor was evaluated by determining lactulose in a pharmaceutical preparation containing a high lactulose concentration, and in different types of milk. Finally, the analytical characteristics of the TTF‐β‐Gal‐FDH‐MPA‐AuE are critically compared with those reported for other recent enzymatic determinations of lactulose. 相似文献
An amphiphilic polymeric conjugate was synthesized from cholic acid and a diamine‐terminated poly(ethylene glycol) containing a galactose moiety (abbreviated as LEC). The LEC conjugate was characterized by FT‐IR and 1H NMR spectroscopy. Investigations using fluorescent probes suggest that the LEC conjugate may associate in water to form core‐shell type nanoparticles. The critical association concentration (CAC) value of these conjugates was estimated to be 0.05 g/L. The LEC nanoparticles were spherical with diameters of around 10 to 30 nm. 相似文献
Insulin transport across the epithelial cell layer in the small intestine was studied using insulin/transferrin conjugates with and without the presence of P(MAA‐g‐EG) microparticles in contact with a co‐culture of Caco‐2/HT29‐MTX cells. The insulin/transferrin conjugate was shown to increase transport relative to pure insulin by a factor of 7, achieving an apparent permeability of 37 × 109 cm · s?1. The presence of P(MAA‐g‐EG) microparticles increased conjugate transport by a factor of 14 times relative to insulin, achieving an apparent permeability of 72.8 × 109 cm · s?1. The presence of the microparticles in solution was found to improve conjugate transport by nearly 100% with little to no change in cell monolayer integrity.
Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self‐assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self‐assembling gold nanoparticles on the surface of L ‐cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well‐defined redox peaks of DA on the GNP/LC/GCE was obtained at Epa=0.197 V and Epc=0.146 V, respectively. And the peak separation between DA and AA is about 0.2 V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10?8–8.5×10?5 mol L?1 and 1.0×10?6–2.5×10?3 mol L?1, with the detection limit of 2.0×10?8 mol L?1 and 3.0×10?7 mol L?1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result. 相似文献
A multiple grafting technique was used to synthesize arborescent‐branched high‐molecular mass poly(2,3‐epoxypropan‐1‐ol). In the first step, linear polyglycidol (M̄n = 10 300) was obtained. Some of the hydroxyl groups were transformed into alcoholate anions in a reaction with potassium tert‐butoxide, and the obtained polyanion was used to initiate the polymerization of 1‐ethoxyethyl glycidyl ether, the glycidol having a protected hydroxyl group. Removing the protecting groups yielded polyglycidol‐graft‐polyglycidol. This procedure was repeated twice to give three generations of comb‐burst branched polyglycidol chains with M̄n of 8.2×104, 7.4×105 and 1.8×106. 相似文献
The in‐site functionalization of 4‐aminothiophenol (4‐ATP) self‐assembled monolayer on gold electrode at physiological pH yields a redox active monolayer of 4′‐mercapto‐N‐phenylquinone diimine (MNPD). The functionalized electrode exhibits excellent electrocatalytic responses towards dopamine (DA) and ascorbic acid (AA), reducing the overpotentials by about 0.22 V and 0.34 V, respectively, with greatly enhanced current responses. Due to its different catalytic activities toward DA and AA, the modified electrode resolves the overlapping voltammetric responses of DA and AA into two well‐defined voltammetric peaks by differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly related to DA and AA concentration in the ranges of 5.0×10?6?1.25×10?4 M and 8.0×10?6?1.3×10?4 M with correlation coefficient of 0.999 and 0.998, respectively. The detective limits (3σ) for DA and AA were found to be 1.2×10?6 M and 2.4×10?6 M, respectively. The modified electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of DA and AA simultaneously in samples with satisfactory results. 相似文献
Galactosaminogalactan (GAG) is a prominent cell wall component of the opportunistic fungal pathogen Aspergillus fumigatus. GAG is a heteropolysaccharide composed of α‐1,4‐linked galactose, galactosamine and N‐acetylgalactosamine residues. To enable biochemical studies, a library of GAG‐fragments was constructed featuring specimens containing α‐galactose‐, α‐galactosamine and α‐N‐acetyl galactosamine linkages. Key features of the synthetic strategy include the use of di‐tert‐butylsilylidene directed α‐galactosylation methodology and regioselective benzoylation reactions using benzoyl‐hydroxybenzotriazole (Bz‐OBt). Structural analysis of the Gal, GalN and GalNAc oligomers by a combination of NMR and MD approaches revealed that the oligomers adopt an elongated, almost straight, structure, stabilized by inter‐residue H‐bonds, one of which is a non‐conventional C?H???O hydrogen bond between H5 of the residue (i+1) and O3 of the residue (i). The structures position the C‐2 substituents almost perpendicular to the oligosaccharide main chain axis, pointing to the bulk solvent and available for interactions with antibodies or other binding partners. 相似文献
A polysaccharide named as AMP‐1 was isolated from the root of Atractylodis macrocephalae Koidz, and purified by ethanol fractionation and gel filtration. The homogeneity of AMP‐1 was determined by HPLC and capillary electrophoresis that gave a single peak. AMP‐1 is composed of galactose and mannose in a molar ratio of 1.0:1.9. Its molecular weight is 3.8 × 103. The structure of ghycan was elucidated by IR, 1H NMR, 13C NMR and methylation analysis, and on the basis of the results was suggested that AMP‐1 contain a backbone of β. (1–2)‐D‐galactose residues with branches of single β‐D‐mannose residue being substituted at the O‐6. Bioactivity assay of AMP‐1 showed that it could inhibit growth of Sarcoma 180 and Lewis pulmonary carcinoma implanted in mice. 相似文献
Abstract Allyl ethers are convenient and widely used protecting groups in synthetic carbohydrate chemistry.2 One of the attractive reactions of the allyl ether group is its ready isomerization into a prop-1-enyl ether function under basic or metal-mediated conditions.2-4 In our research projects to extend galactosyltransferase reactions to the enzymic syntheses of βGal 1,1-linked sugars,5 1-O-allyl galactopyranoside was needed as a key synthetic intermediate. Anhydrous cation exchange resin (AmberlystR15:Rohm & Haas Co.) was chosen as the acidic catalyst owing to its ease of handling and removal. In this paper we report an unexpected result of this reaction which gave allyl 4,6-O-propylidene galactopyranoside from galactose and Amberlyst in refluxing allyl alcohol. On treatment of galactose (200 mg) and Amberlyst (100 mg) in allyl alcohol (5 mL) at 100–110 °C, TLC analysis (silica gel, acetonitrile:water, 10:1) indicated that the allyl glycosylation was completed within 15 min, affording allyl D-galactopyranoside. 相似文献
A novel route for the fabrication of neodymium hexacyanoferrate (NdHCF) modified glassy carbon electrodes (GCE) was proposed. The morphological characterization of NdHCF was examined by scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR). The performances of the NdHCF/GCE were characterized with cyclic voltammetry and differential pulse voltammograms (DPV). The modified electrode showed excellent electrocatalytic effect and high stability toward the electrochemical oxidation of dopamine (DA) in phosphate buffer solution (pH 5.5) with a diminution of the anodic overpotential of 155 mV. The anodic peak currents increased linearly with the concentration of DA from 5.0×10?7 to 6.0×10?4 M with a detection limit of 1.0×10?8 M (S/N=3). The most important is that the modified electrode could be used for the determination of DA in the presence of an ascorbic acid concentration as large as 100‐fold that of DA. The proposed method was used to determine DA in DA‐hydrochloride injection and showed excellent sensitivity and recovery. The ease of fabrication, high stability, and low cost of the modified electrode are the promising features of the proposed sensor. 相似文献
The separation of polysaccharides is time consuming. We developed and optimized a type‐J counter‐current chromatography system with a novel tri‐rotor spiral coil column for the rapid separation of polysaccharides. The optimal composition of an aqueous PEG1000/K2HPO4/KH2PO4 system was found to be 14:16:14 w/w/w where the lower phase was the mobile phase. Optimal performance was achieved at a column rotational speed, temperature, and flow rate of 1200 rpm, 45°C, and 3.0 mL/min, respectively. The mobile phase was pumped from the inner terminal in a ‘‘head‐to‐tail’’ elution mode. Polysaccharide LCP‐1 (10.7 mg) was successfully obtained in high purity in one step from 50.0 mg of a crude polysaccharide extracted from the lychee fruit (Litchi chinensis) within 100 min. LCP‐1 possess a number‐average molecular weight and weight‐average molecular weight of 1.05 × 105 and 1.59 × 105 kDa, respectively. The monosaccharide composition consists of the molar ratio of glucose, galactose, and arabinose of 1.3:3.5:1. 相似文献
A new sensor, gold‐6‐amino‐2‐mercaptobenzothiazole (6A2MBT), was fabricated via a self‐assembly procedure. Electrochemical properties of the monolayer were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified electrode showed excellent antifouling property against the oxidation products of DA, allowed us to construct a dynamic calibration curve with two linear parts, 1.00×10?6 to 3.72×10?4 and 3.72×10?4 to 6.42×10?4 M DA, with correlation coefficients of 0.997 and 0.992 and a detection limit of 1.57×10?7 M DA by using differential pulse voltammetry (DPV), respectively. Finally, the performance of the Au‐6A2MBT modified electrode was successfully tested for electrochemical detection of DA in a pharmaceutical sample. 相似文献
Galactomannans with galactose:mannose ratios 1:1.48 and 1:1.33, [α]D +67.9 and +76.4°, [η] 870.3 and 1337.1 mL/g, and molecular weights 999 and 1549 kDa, respectively, were isolated in 0.59
and 4.65% yields (of seed mass) from seeds of Astragalus alpinus and A. tibetanus (Fabaceae). Physicochemical methods (CrO3 oxidation; methylation–GC/MS; IR, NMR, and 13C spectroscopy) found that the main polysaccharide chain consisted of 1,4-β-D-mannopyranose units substituted 67.5% (A. alpinus) and 75.2% (A. tibetanus) at the C-6 position by single α -D-galactopyranose units. The contents of mannobiose blocks Man–Man, (Gal)Man–Man/Man–Man(Gal), and (Gal)Man–Man(Gal) variously
substituted with galactose were according to 13C NMR spectroscopy 15.9, 55.5, and 28.6% in A. alpinus galactomannan and 9.9, 42.3, and 47.8% in A. tibetanus galactomannan. 相似文献
A sensitive and selective electrochemical method for the determination of dopamine (DA) was developed using a calix[4]arene crown‐4 ether (CACE) film modified glassy carbon electrode (GCE).The modified electrode exhibited good electrocatalytic activity for electrochemical oxidation of DA in the pH 6.00 Britton–Robinson buffer solution, and ascorbic acid (AA) did not interfere with it. The diffusion coefficient (D=2.7×10?5 cm2 s?1), and the kinetic parameter such as the electron transfer coefficient (α=0.54) of DA at the surface of CACE were determined using electrochemical approaches. The catalytic oxidation peak currents showed a linear dependence on the DA concentration and a linear analytical curve was obtained in the range of 2.0×10?5–1.0×10?3 M of DA with a correlation coefficient of 0.9990. The detection limit (S/N=3) was estimated to be 3.4×10?6 M. This method was also examined for the determination of DA in an injection sample. In addition, effects of possible interferences were investigated. The present work shows the potential of the proposed method for the fabrication of a modified electrode, as it can be effectively used for voltammetric detection of DA. 相似文献