在线衍生微流控芯片电泳和激光诱导荧光法测定单细胞中谷胱甘肽

微流控分析芯片的网络结构和微米通道尺寸适合于单细胞进样、控制和分离分析^[1~4].在测定细胞内容物时,大多采用柱前细胞内衍生法^[1,2,4],但操作复杂,需多次离心分离,且能透过细胞膜标记胞内组分的荧光试剂较少.     

JONES型电导池测量的LCR电桥等效电路选择

JONES电导池系统的交流阻抗由电极过程的相关阻抗和电极间溶液的电阻两部分组成,可用适当的等效电路模拟。采用LCR电桥测量JONES电导池中溶液的电阻时需要选择合适的等效电路为模型解析测量的交流阻抗。通过等效电路的分析发现,选择串联电路作为LCR电桥的解析等效电路测量JONES型电导池中溶液的电阻时引入的误差比并联电路小。     

碳载Pt和PtRu催化剂的甲醇电氧化比较

利用电化学方法对商用Pt/C和PtRu/C催化剂在酸性介质中的甲醇电氧化进行了比较研究.动电位和恒电位氧化实验结果皆表明PtRu/C比Pt/C对甲醇电催化活性高.PtRu合金的形成不仅改变了催化剂表面对氢的吸附性质,而且使氧化物还原峰电位向阴极方向移动.Ru与甲醇的相互作用为温度活化过程,需要较高的温度.     

Establishment of a metabolic pathway to introduce the 3-hydroxyhexanoate unit into LA-based polyesters via a reverse reaction of β-oxidation in Escherichia coli LS5218

New lactate (LA)-based terpolymers, P[LA-co-3-hydroxybutyrate (3HB)-co-3-hydroxyhexananoate (3HHx)]s, were produced in recombinant Escherichia coli LS5218 harboring three genes encoding LA-polymerizing enzyme (LPE), propionyl-coenzyme A (CoA) transferase (PCT) and (R)-specific enoyl-CoA hydratase (PhaJ4). When the recombinant LS5218 was grown on glucose with the feeding of butyrate, 3HB-CoA and 3HHx-CoA were supplied, probably via reverse reactions of the β-oxidation pathway and PhaJ4. LPE copolymerized the two monomers 3HB-CoA and 3HHx-CoA with LA-CoA, which was generated by PCT, to yield the terpolymers. Gas chromatography analysis revealed that the terpolymers consisted of 2.7-34 mol% LA, 38-81 mol% 3HB and 17-33 mol% 3HHx units, which can be varied depending on the butyrate concentration fed in the medium. In addition, ¹H-¹³C COSY NMR analysis provided evidence for a linkage between LA and 3HHx units in the polymer.     

The mean activity coefficients of LaCl3 in dilute aqueous solution at 298.15 K

The electromotive forces of a symmetrical concentration cell with transference, Ag; AgCl|LaCl₃ (m*):LaCl₃ (m)|AgCl; Ag, were measured over the concentration range from 8.762 × 10⁻⁴ mol kg⁻¹ to 6.788 × 10⁻² mol kg⁻¹ at 298.15 K to obtain the mean activity coefficients of LaCl₃. The mean activity coefficient for reference solution at 298.15 K and the ion size parameter for LaCl₃ in the extended Debye–Hückel equation are evaluated by using an approach extrapolating concentration to unlimited dilution. A modified Debye–Hückel equation with new parameters has been established for the studied concentration range. A comparison is done of the thermodynamic data of LaCl₃ that are determined by this experiment with those reported by previous literatures, and evaluated by some models.     

Analysis of amino acids and biogenic amines in breast cancer cells by capillary electrophoresis using polymer solutions containing sodium dodecyl sulfate

We describe simultaneous analysis of naphthalene-2,3-dicarboxaldehyde (NDA)-amino acid and NDA-biogenic amine derivatives by CE in conjunction with light-emitting diode-induced fluorescence detection using poly(ethylene oxide) (PEO) solutions containing sodium dodecyl sulfate (SDS). After sample injection, via EOF 0.1% PEO prepared in 100 mM TB solution (pH 9.0) containing 30 mM SDS entered a capillary filled with 0.5 M TB solution (pH 10.2) containing 40 mM SDS. Under this condition, 14 NDA-amino acid and NDA-amine derivatives were separated within 16 min, with high efficiency ((1.0–3.2) × 10⁵ theoretical plates) and sensitivity (LODs at S/N = 3 ranging from 2.06 to 19.17 nM). In the presence of SDS and PEO, analytes adsorption on the capillary wall was suppressed, leading to high efficiency and reproducibility. The intraday analysis RSD values (n = 3) of the mobilities for the analytes are less than 0.52%. We have validated the practicality of this approach by quantitative determination of 9 amino acids in breast cancer cells (MCF-7) and 10 amino acids in normal epithelial cells (H184B5F5/M10). The concentrations of Tau and Gln in the MCF-7 cells were different than those in the H184B5F5/M10 cells, respectively. Our results show the potential of this approach for cancer study.     

New separation methodologies for the distinction of the growth phases of Saccharomyces cerevisiae cell cycle

In the present work two separation techniques, namely the gravitational field-flow fractionation (GrFFF) and the reversed-flow gas chromatography (RFGC), are proposed for the distinction of the growth phases of Saccharomyces cerevisiae (AXAZ-1) yeast cycle at different temperatures (30 °C, 25 °C, 20 °C, and 15 °C) and pH (2.0, 3.0, 4.0 and 5.0) values. During the fermentation processes, differences observed in the peak profiles, obtained by GrFFF, can be related with the unlike cell growth. The distinction of the phases of AXAZ-1 cell cycle with the GrFFF, was also confirmed with the RFGC technique, which presented similar fermentation time periods for the alcoholic fermentation phases. Simultaneously, the reaction rate constant for each phase of the fermentation process and the activation energies were determined with the aid of the RFGC technique. Finally, the application of both the GrFFF and the RFGC techniques, in combination with high-performance liquid chromatography, allowed us to find the ideal experimental conditions (temperature and pH) for the alcoholic fermentation by AXAZ-1. The results indicate that S. cerevisiae cells performed better at 30 °C, whereas at lower temperatures decreases in the fermentation rate and in the number of viable cells were observed. Moreover, the pH of the medium (pH 5.0) resulted in higher fermentation rates and ethanol productivities.     

肾小管上皮细胞损伤及其诱导草酸钙晶体成核

肾上皮细胞损伤可促进肾结石形成.本文采用过氧化氢(H2O2)对人类肾小管上皮细胞(HKC)进行了氧化损伤,采用扫描电子显微镜(SEM)、X射线衍射分析(XRD)和倒置显微镜观察了HKC损伤前后的形态变化及其调控草酸钙(CaOxa)晶体成核、生长的差异;采用zeta电位分析仪检测了损伤前后HKC表面的zeta电位变化.结果表明,H2O2能明显地损伤HKC,降低细胞活性,且在H2O2浓度范围0.1～0.5mmol/L、作用时间0.5～1.5h内具有明显的剂量和时间的依赖性;使用0.5mmol/LH2O2作用1.5h可使HKC损伤达到饱和状态.HKC损伤程度增加后,其诱导的晶体数量显著增加,但晶体尺寸增加不明显(P0.05),表明损伤细胞诱导尿石症形成主要是增加晶体的成核位点而非促进晶体的生长.本文所建立的HKC氧化损伤的模型有助于进一步阐明CaOxa结石形成的细胞机制.     

Neuroprotection signaling pathway of nerve growth factor and brain-derived neurotrophic factor against staurosporine induced apoptosis in hippocampal H19-7 cells

Neurotrophins protect neurons against excitotoxicity; however the signaling mechanisms for this protection remain to be fully elucidated. Here we report that activation of the phosphatidyl inositol 3 kinase (PI3K)/Akt pathway is critical for protection of hippocampal cells from staurosporine (STS) induced apoptosis, characterized by nuclear condensation and activation of the caspase cascade. Both nerve growth factor (NGF) and brain-derived growth factor (BDNF) prevent STS-induced apoptotic morphology and caspase-3 activity by upregulating phosphorylation of the tropomyosin receptor kinase (Trk) receptor. Inhibition of Trk receptor by K252a altered the neuroprotective effect of both NGF and BDNF whereas inhibition of the p75 neurotrophin receptor (p75NTR) had no effect. Impairment of the PI3K/Akt pathway or overexpression of dominant negative (DN)-Akt abolished the protective effect of both neurotrophins, while active Akt prevented cell death. Moreover, knockdown of Akt by si-RNA was able to block the survival effect of both NGF and BDNF. Thus, the survival action of NGF and BDNF against STS-induced neurotoxicity was mediated by the activation of PI3K/Akt signaling through the Trk receptor.