电催化剂Pt—WO3用作葡萄糖传感器工作电极性能的研究

用铂金属和溶解和三氧化钨电化学沉积制备Ｐｔ／ＷＯ３电极,利用流动分析等方法研究了电极作为葡萄糖传感器工作电极的性能。结果表明,该电极具有工作电位低、催化活性高、响应快、重复性好、抗干扰能力强及使用寿命长等特点。在２×１０＾－３－４×１０６－２ｍｏｌ／Ｌ范围内,峰高Ｉｐ与葡萄糖浓度呈现较好的线性关系。     

Antioxidants from a heated histidine-glucose model system. I: Investigation of the antioxidant role of histidine and isolation of antioxidants by high-performance liquid chromatography

The radical-combining activity of Maillard reaction products [MRP_(aq)], produced by heating d-glucose and l-histidine (3:1) in a 0.1 M phosphate buffer for 10 h at 105°C (final pH 6.53), was estimated directly by means of a diphenylpicrylhydrazyl radical (DPPH^·) method. Additionally, the indirect methods of peroxide values changes (oven test), hexanal formation, and protection factors (Rancimat method) were determined on a lipid model system that consisted of sunflower seed oil/water (1:2), emulsified with 3% (w/w) Tween 40. Results from the DPPH^· method showed a potential antioxidant activity of MRP_(aq), which was confirmed by the indirect methods. Surprisingly, histidine in solution alone (heated or not) exhibited an antioxidant activity greater than or similar to the MRP_(aq) activity in the indirect methods with the lipid model system, in contrast to the results from the DPPH^· method. The suitability of various solvents for extraction of potential antioxidant compounds from freeze-dried MRP_(aq) was examined, and ethanol extracts showed the greatest activity by the DPPH^· method. Consequently, the ethanol extract of freeze-dried MRP_(aq) was separated by means of preparative reverse-phase high-performance liquid chromatography (HPLC) with a 0.05 M phosphate buffer (pH 4.4)/water/acetonitrile gradient system. The antioxidant activity of the eluate was measured through the DPPH^· method, and a fraction (Fraction A) with antiradical activity was further purified by preparative HPLC. Fraction B was collected, and its freeze-dried residue exhibited potent antiradical activity, significantly greater than that of the same level of n-propyl gallate.     

Novel porous matrix and bioreactors for high density cultures of insulinoma cell lines: Insulin secretion and response to glucose

This paper describes the use of a novel porous matrix, Porocell, for high density, tissue-like culture of two insulinoma cell lines, CRI-D2 and CRI-D11. Both these cell lines have previously been shown not to secrete insulin in response to glucose. Porocell is a macro-porous, polymeric material manufactured in the shape of discs that are 6·2 mm in diameter and 2 mm in thickness. Insulinoma cells were cultured in two different mini-bioreactors, each containing six Porocell discs inoculated with 2·5 × 10⁶ cells per disc. In surface aerated, stirred bioreactors, the insulinoma cells grew as closely packed dense cell sheets penetrating deep into the pores of Porocell. In a second type of system, a packed-bed perfused mini-bioreactor, flat, extended monolayers of cells were observed growing throughout the Porocell matrix. In both bioreactor configurations, viable cell populations were maintained for 30 days because of the excellent oxygen and nutrient transfer properties of Porocell. CRI-D2 insulinoma cells cultured in static flasks and on Porocell did not show any insulin secretion in response to 30 min exposures in media supplemented with 5·5–16·7 mmol dm⁻³ glucose. However, in long term (14–19 day) cultures, CRI-D2 cells growing in Porocell secreted low, but measurable amounts (25–35 pmol dm⁻³) of insulin in medium supplemented with elevated (14·5 mmol dm⁻³) glucose concentrations. The glucose uptake rates of cells cultured in 4·0 mmol dm⁻³ glucose increased linearly from 1·0 to 2·3 mmol dm⁻³ day⁻¹ over a period of 19 days. At 14·5 mmol dm⁻³ glucose concentration, the uptake rate increased from 1·0 to 7·05 mmol dm⁻³ day⁻¹ over the same period of culture. Contrary to previous studies, we have demonstrated that the CRI-D2 cell line cultured at high cell density in Porocell is capable of secreting insulin when exposed to prolonged and elevated concentrations of glucose. The Porocell mini-bioreactors are easy to use, robust systems that can be used for long-term studies of primary and tumorgenic islet cell function and response to secretagogues. © 1998 SCI.     

Catalytic dehydration of glucose to 5‐hydroxymethylfurfural with a bifunctional metal‐organic framework

Glucose conversion to 5‐hydroxymethylfurfural (HMF) generally undergoes catalytic isomerization reaction by Lewis acids followed by the catalytical dehydration to HMF with Brönsted acid. In this work, a sulfonic acid functionalized metal‐organic framework MIL‐101(Cr)‐SO₃H containing both Lewis acid and Brönsted acid sites, was examined as the catalyst for γ‐valerolactone‐mediated cascade reaction of glucose dehydration into HMF. Under the optimal reaction conditions, the batch heterogeneous reaction gave a HMF yield of 44.9% and selectivity of 45.8%. Reaction kinetics suggested that the glucose isomerization in GVL with 10 wt % water follows the second‐order kinetics with an apparent activation energy of 100.9 kJ mol^?1. Continuous reaction in the fixed‐bed reactor showed that the catalyst is highly stable and able to provide a steady HMF yield. This work presents a sustainable and green process for catalytic dehydration of biomass‐derived carbohydrate to HMF with a bifunctional metal‐organic framework. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4403–4417, 2016     

The Impact of Soy Isoflavones on MCF-7 and MDA-MB-231 Breast Cancer Cells Using a Global Metabolomic Approach

Despite substantial research, the understanding of the chemopreventive mechanisms of soy isoflavones remains challenging. Promising tools, such as metabolomics, can provide now a deeper insight into their biochemical mechanisms. The purpose of this study was to offer a comprehensive assessment of the metabolic alterations induced by genistein, daidzein and a soy seed extract on estrogen responsive (MCF-7) and estrogen non-responsive breast cancer cells (MDA-MB-231), using a global metabolomic approach. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that all test compounds induced a biphasic effect on MCF-7 cells and only a dose-dependent inhibitory effect on MDA-MB-231 cells. Proton nuclear magnetic resonance (¹H-NMR) profiling of extracellular metabolites and gas chromatography-mass spectrometry (GC-MS) profiling of intracellular metabolites confirmed that all test compounds shared similar metabolic mechanisms. Exposing MCF-7 cells to stimulatory concentrations of isoflavones led to increased intracellular levels of 6-phosphogluconate and ribose 5-phosphate, suggesting a possible upregulation of the pentose phosphate pathway. After exposure to inhibitory doses of isoflavones, a significant decrease in glucose uptake was observed, especially for MCF-7 cells. In MDA-MB-231 cells, the glutamine uptake was significantly restricted, leading to alterations in protein biosynthesis. Understanding the metabolomic alterations of isoflavones represents a step forward in considering soy and soy derivates as functional foods in breast cancer chemoprevention.     

Comparison of backbone structures of glucose isomerase from Streptomyces and Arthrobacter

The C backbones of the glucose isomerase molecules of Streptomycesrubiginosus and Arthrobacter have been determined by X-ray crystallographyand compared. Each molecule is a tetramer of eight-stranded/ß barrels, and the mode of association of the tetramersis identical in each case. The Arthrobacter electron densityshows four additional amino acids at the carboxyl terminus.There is also an insertion of six amino acids at position 277,and two individual insertions at about positions 348 and 357(numbering according to the Streptomyces structure). There isa close structural homology throughout the whole molecule, whichis most accurate up to position 325. The r.m.s. displacementfor 315 homologous C positions up to this position is 0.92 Å.     

HPLC-ELSD法同时测定天麻中天麻素、葡萄糖、果糖和蔗糖含量

建立天麻中活性成分天麻素及风味物质果糖、葡萄糖和蔗糖的含量同时测定方法。以氨基色谱柱为分离柱,采用高效液相色谱-蒸发光散射检测器（high performance liquid chromatography-evaporative light scattering detector,HPLC-ELSD）对4种成分进行分离、分析,在优化的色谱条件下天麻素、果糖、葡萄糖和蔗糖分离度及色谱峰峰形均良好,可实现天麻中4种成分含量同时测定。采用主成分分析（principal component analysis,PCA）和聚类分析（cluster analysis,CA）方法对不同产地、批次天麻中4种成分含量进行分析。结果表明,不同批次的天麻样品中4种成分含量有明显差异,其中贵州产地的天麻样品目标成分含量最高,而且质量分布均匀,可与其他产地天麻进行区分;云南、陕西、湖北地区中的同一产地样品质量分布不均,离散度较高,无法被明显区分。     

基于代谢组学分析Slr0643蛋白在调控集胞藻PCC6803葡萄糖混养适应中的重要性

本研究文采用集胞藻PCC6803野生型藻株和Slr0643敲除突变体(Δslr0643)藻株,通过生理实验和基于气相色谱-质谱联用(GC-MS)技术的植物代谢组学分析,对Slr0643蛋白调控集胞藻PCC6803葡萄糖混养适应的机制进行探讨.在2.5 mM葡萄糖混养条件下,野生型藻株的生长速率较光自养条件明显加快,而Δ...     

羟基保护法制备聚(D-乳酸-葡萄糖)共聚物及其性能研究

以α-D-葡萄糖为原料,采用羟基保护法制备1,2:5,6-双-O-异丙叉基-α-D-呋喃葡萄糖(ODG),并与聚D-乳酸(PDLA)熔融共聚合成聚(D-乳酸-1,2:5,6-双-O-异丙叉基-α-D-呋喃葡萄糖)共聚物(PDLAODG),然后水解脱羟基制备聚(D-乳酸-葡萄糖)共聚物(PDLAG).采用核磁共振氢谱、傅...     

马齿苋多糖对高糖诱导的人晶状体上皮细胞发生上皮间质转化的影响

目的 观察马齿苋多糖对高糖作用下永生系人晶状体上皮细胞(SRA01/04)上皮间质转化的影响。方法 体外培养SRA01/04细胞,将传代的细胞随机分为正常对照组、高糖组、高糖+马齿苋多糖组,分别用含5.5mmol/L葡萄糖、30mmol/L葡萄糖、30mmol/L葡萄糖+0.5mg/mL马齿苋多糖的培养基培养48h,于培养的0h、6h、12h、24h、48h在倒置显微镜下分别观察三组的细胞形态学变化;48h后Western-blot检测细胞ZO-1、E-cadherin及α-SMA、Vimentin的蛋白表达变化,结果与对照组相比,高糖组细胞随时间延长细胞变长出现成纤维改变,细胞数量也逐渐减少;高糖联合马齿苋多糖组与正常组的形态变化基本趋于一致,没有随着时间延长而发生明显的梭形改变,与对照组相比,高糖组ZO-1、E-cadherin表达下降(P<0.01),α-SMA和Vimentin的表达上升(P<0.01);高糖联合马齿苋多糖组ZO-1、E-cadherin表达下降(P<0.05),α-SMA和Vimentin的表达上升(P<0.05)?与高糖组相比,高糖联合马齿苋多糖组ZO-1、E-cadherin表达上升(P<0.01),α-SMA和Vimentin的表达下降(P<0.01)。结论 高糖可以诱导晶状体上皮细胞发生上皮间质转化,马齿苋多糖可以抑制这一过程。