For the first time, a diffusive gradients in thin films (DGT) device using molecularly imprinted polymer (MIP) as the binding agent and nylon membrane (NM) as the diffusive layer (NM-MIP-DGT) has been developed for sampling 4-chlorophenol (4-CP) in water. The MIP was prepared by precipitation polymerization with methacrylic acid as monomer and ethyleneglycoldimethacrylate as cross-linker. The diffusion coefficient of 4-CP through NM was obtained to be 0.788 ± 0.040 μ cm2 s−1 by diffusion cell method. The ratio was 1.01 ± 0.05 (mean ± standard deviation) for the concentration of 4-CP sampled by NM-MIP-DGT and analyzed by HPLC method to the total concentration of 4-CP in the synthetic solution where free 4-CP species dominated. The results showed that NM-MIP-DGT could sample 4-CP in synthetic solution accurately. The performance of NM-MIP-DGT for sampling 4-CP was independent of pH in the range of 3–7 and ionic strength in the range of 0.0001–0.1 mol L−1 NaCl solution. The concentration of free form of 4-CP sampled by NM-MIP-DGT decreased with the increasing concentration of dissolved organic carbon in different water samples due to the electrostatic interaction of natural organic compounds with 4-CP. 1.8 mg L−1 of the free form of 4-CP was determined by HPLC which was sampled by NM-MIP-DGT in an intermediate untreated industrial effluent. The NM-MIP-DGT can be a potential passive tool for sampling the free form of 4-CP in water. 相似文献
Dynamic, continuous, and simultaneous multi-analysis of transmitters is important for the delineation of the complex interactions between the neuronal and intercellular communications. But the analysis of the whole repertoire of classical transmitters of diverse structure is challenging due to their different physico-chemical properties and to their high polarity feature which leads to poor retention in traditional reversed-phase columns during LC–MS analysis. Here, an online microdialysis coupled with hydrophilic interaction chromatography–tandem mass spectrometry (online MD-HILIC–MS/MS) detection method was developed for the simultaneous measurement of the repertoire of classical transmitters (acetylcholine, serotonin, dopamine, norepinephrine, glutamate, GABA, and glycine). Stable isotope labeled internal standards and authentic matrix have been applied to guarantee reliable results. The method was successfully employed to reveal the characteristics of transmitter release from embryonal carcinoma stem cells. The method features simple procedure (no sample preparation), high recovery (≥73%), high accuracy (89.36% ≤ RE ≤ 116.89%), good reproducibility (2.18% ≤ RSD ≤ 14.56%), and sensitive limits of detection (2 pg for acetylcholine, serotonin, and glutamate, 10 pg for dopamine, norepinephrine, GABA, and glycine). It can be flexibly applied to determine the contents of the classical transmitters in other biological matrix samples with minor changes. 相似文献
A newly-developed method of complete separation and sensitive determination of o-, m-, and p-aminobenzoic acid isomers was achieved by combining open-tubular columns for capillary electrochromatography (OT-CEC) and online sample stacking. In this study, spherical gold nanoparticles were modified by a covalent attachment of mono-6-thio-β-cyclodextrin, and OT-CEC was formed by immobilizing cyclodextrin-modified gold nanoparticles (CD-AuNP) on prederivatized 3-mercaptopropyl-trimethoxysilane fused-silica capillaries. Based on the theory of moving chemical reaction boundary, effects of several important factors such as the pH and concentration of running buffer and the conditions of stacking analytes were optimized. The optimized separations were carried out in 58 mmol/L HAc buffer at pH 3.0 using a capillary coated with CD-AuNP, while the optimized concentration was carried out in 50 mmol/L disodium hydrogen phosphate (pH 9.5). The linear ranges for m-, p-, and o-aminobenzoic acid were from 5.0 × 10−4–0.1, 5.0 × 10−4–0.1 and 1.0 × 10−4–0.1 mmol/L, respectively. And the detection limits (S/N = 3) were as low as 8.22 × 10−5, 8.21 × 10−5, and 3.76 × 10−5 mmol/L for m-, p-, and o-aminobenzoic acid, respectively. The run-to-run, day-to-day, and column-to-column reproducibilities of migration time were satisfactory with relative standard deviation values of less than 4.5 % in all cases. This method was successfully used in determining procaine hydrochloride injection sample with recoveries in the range of 96.1–106.6 % and relative standard deviations less than 5.0 %.
Chemical synthesis of a trisaccharide related to the cytotoxic triterpenoid saponins isolated from the bark of Albizia procera has been accomplished through a concise stepwise glycosylation strategy starting from commercially available D ‐xylose, 2‐acetamido‐2‐deoxy‐D ‐glucose and L ‐arabinose. The target trisaccharide was designed with a 4‐methoxyphenyl (MP) aglycone to extend the scope of conversion to suitable glycoconjugates via selective removal of 4‐methoxyphenyl (MP) group. An unexpected phenomenon, i.e., the arabinosyl residue assumed the 1C4 conformation instead of the typical 4C1 form, was observed. Deprotection could restore the normal conformation. 相似文献
The aim of this study is to analyze the growth and substance metabolism of neural stem cells (NSCs) cultured in biological collagen-based scaffolds. Mass transfer and metabolism model of glucose, lactic acid, and dissolved oxygen (DO) were established and solved on MATLAB platform to obtain the concentration distributions of DO, glucose, and lactic acid in culture system, respectively. Calculation results showed that the DO influenced their normal growth and metabolism of NSCs mostly in the in vitro culture within collagen-based scaffolds. This study also confirmed that 2-mm thickness of collagen scaffold was capable of in vitro cultivation and growth of NSCs with an inoculating density of 1?×?106 cells/mL. 相似文献
Purification and characterization of a chymosin from Rhizopus microsporus var. rhizopodiformis were investigated in the present study. A newly isolated R. microsporus var. rhizopodiformis F518 produced a high level of milk-clotting activity (1,001 SU/mL). A chymosin from the fungus was purified 3.66-fold with a recovery yield of 33.2 %. The enzyme appeared as a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with a molecular mass of 37.0 kDa. It was optimally active at 60 °C and was stable up to 40 °C. The purified enzyme was an acid protease with an optimum pH of 5.2 and retained 80 % of residual activity within pH 2.0–8.0. The inhibition of 96 and 100 % by pepstatin A at 0.01 and 0.02 mM, respectively, revealed that the enzyme is an aspartic protease. Thus, high milk-clotting activity of the chymosin with good stability will strengthen the potential use of the chymosin as a substitute for calf rennet in cheese manufacturing. 相似文献
A new near-neutral pH near-infrared (NIR) fluorescent probe utilizing a fluorophore–receptor molecular framework that can modulate the fluorescence emission intensity through a fast photoinduced electron transfer process was developed. Our strategy was to choose tricarbocyanine (Cy), a NIR fluorescent dye with high extinction coefficients, as a fluorophore, and N-methylpiperazine (MP) as a receptor. The pH titration indicated that MP-Cy can monitor the minor physiological pH fluctuations with a pKa of ~7.10 near physiological pH, which is valuable for intracellular pH researches. The probe responds linearly and rapidly to minor pH fluctuations within the range of 3.05–7.10 and exhibits strong dependence on pH changes. As expected, the real-time imaging of cellular pH and the detection of pH in situ was achieved successfully in living HepG2 cells by this probe. It is shown that the probe effectively avoids the influence of autofluorescence and native cellular species in biological systems and meanwhile exhibits high sensitivity, good photostability, and excellent cell membrane permeability. 相似文献
Herein, a facile and noncovalent modification for multiwalled carbon nanotubes (MWNTs) is adopted by the self-polymerization of dopamine (DOPA). And, the polydopamine-coated MWNTs (D-MWNTs) were further incorporated into poly(l-lactide) (PLLA) matrix through the solvent-casting method. It is found that the D-MWNTs tend to be well dispersed in PLLA matrix than the pristine MWNTs and the D-MWNTs that can act as heterogeneous nucleators that evidently affect the morphology and crystallization behavior of PLLA. In addition, the significant improvement of dispersion and the interface interaction of PLLA/D-MWNTs, via dopamine coating between the MWNTs and PLLA matrix, results in enhanced mechanical and thermal properties and electrical conductivity. This facile methodology is believed to afford broad application potential in carbon nanotubes (CNTs)-based polymer nanocomposites. 相似文献