Synthesis and properties of porous CLEAs lipase by the calcium carbonate template method and its application in biodiesel production

In this work, porous cross-linked enzyme aggregates (p-CLEAs) were synthesized by the in situ co-precipitation method using CaCO₃ microparticles as templates. The preparation procedure involved the immobilization of crude lipase as CLEAs via precipitation with ammonium sulfate and entrapping these lipase molecules into the CaCO₃ templates, followed by DTT (dithiothreitol)-induced assembly of lipase molecules to form lipase microparticles (lipase molecules were assembled into microparticles internally using disulfide bonds within the lipase molecules as the molecular linkers and stimulated by dithiothreitol); finally, the removal of CaCO₃ templates was performed by EDTA to form pores in CLEAs. The scanning electron microscopy analysis of p-CLEAs showed a porous structure. p-CLEAs showed obvious improvement in thermal stability (after incubation at 65 °C, p-CLEAs lipase retained 86% relative activity, while free lipase retained only 33.67%) and pH stability (p-CLEAs relative activity was over 90% while for free lipase, the relative activity ranged from 72% to 89% from pH 6 to 9) than free lipase and could hold relatively high activity retention without activity loss at 4 °C for more than six months. The application of p-CLEAs in producing biodiesel showed a higher degree of conversion. The conversion of fatty acid methyl ester (FAME) was 89.7%; this value was higher by approximately 7.4% compared to that of the conventional CLEAs under the optimized conditions of a methanol–oil molar ratio of 6 : 1, with a p-CLEAs lipase dose of 20% and water content of 3% at 45 °C for 24 h. The FAME conversion remained greater than 70% even after reusing the p-CLEAs lipase for 8 reactions. The results demonstrated that the p-CLEAs lipase is suitable for applications in the preparation of biodiesel.

Porous cross-linked enzyme aggregates (p-CLEAs) were synthesized. This p-CLEAs presented a complete structure with abundant channels, large specific surface and more efficient catalytic effect compared with conventional CLEAs.     

Characterization of novel non-protein-coding RNA from V. cholerae O1 El Tor

IntroductionA plethora of bacterial small RNA (npcRNA) has progressively gained momentum in revising our apprehension on their engagement as key player in modulating general stress responses and bacterial virulence. Vibrio cholerae serogroup O1, biotype El Tor causes cholera, which is an acute dehydrating, watery diarrhoeal disease, with epidemic and pandemic potential. We have identified a total of 224 novel npcRNA candidates from V. cholerae El Tor by experimental RNomics strategy. Objective: To characterize the expression profile and functionality of identified novel npcRNA from V. cholerae O1 El Tor.MethodsDifferential expression of selected npcRNA candidates was studied using Northern blot analysis under various stress conditions in the background wild type strain as well as Hfq protein knockout strain. Interaction of the selected npcRNA candidates with Hfq protein was also evaluated.Results & DiscussionTwo intergenic npcRNA genes were incorporated as targets in a multiplex PCR that could be a crucial tool in molecular epidemiological study of V. cholerae. Differential expression of 9 selected npcRNA candidates under a series of stress conditions was demonstrated. Interestingly, one of the candidate, Vc_npcR_3853 was demonstrated to have the potential in negatively regulating the expression of VC0092 and VC0304, which encodeLexA repressor and guanosine-5′-triphosphate, 3′-diphosphate pyrophosphatase, respectively.ConclusionCollectively, differential expression of those npcRNA candidates under wild type and Hfq knockout background as well as their interaction with Hfq protein set the stage towards discerning the functional role of these novel npcRNAs in orchestrating pathophysiology of V. cholerae El Tor.     

Control of bursting behavior in neurons by autaptic modulation

Firing properties of biological neurons have long been recognized to be determined by extrinsic synaptic afferents that neurons receive and intrinsic ionic mechanisms that neurons possess, however, previous researches have also demonstrated that firing behavior of single neurons can be modulated by the neurons themselves, realized by the autapses. Thus in this investigation, we argued that how autaptic modulations shape the bursting behavior of biological neurons. We considered the issue from the following two aspects: autaptic-excitation and -inhibition. Our results suggested that for autaptic-excitation, under the condition of relatively weak stimulus, regular bursting was more incline to occur when the autaptic strength was weak, while regular spiking was more likely to appear when the autaptic strength was strong. However, larger stimulus would diminish the portion of bursting, but increase the portion of spiking. For autaptic-inhibition, under relatively weak stimulus, a wide range of regular bursting emerges when the autaptic strength was small, but when stronger stimulus were applied, the range of regular bursting shrinked into a small region. Meanwhile, we observed that synaptic delays have no obvious effects in the case of autaptic-excitation, while a subtle effect of synaptic delays was observed in the case of autaptic-inhibition. These results showed that bursting behavior of neurons could be controlled and modulated by the autaptic mechanisms that biological neurons intrinsically possess, and the final results may further promote the understanding in the generation of various neuronal firing patterns.     

商业保险机构参与长期护理保险经办模式比较——基于北京市海淀区、青岛市的分析

本文从公私合作角度比较商业保险机构参与长期护理保险经办的两种典型模式的异同及应用前景。本文选取了北京市海淀区、青岛市作为典型模式代表。两种模式中商保机构均是由市区政府招标引入,并委托相应机构进行监管,但海淀区模式中商保机构参与度比青岛市模式更深;在盈亏承担方面,海淀区模式比青岛市模式的商保机构承担更多盈亏风险。两种模式的应用前景方面,海淀区模式适合在人口多、经济发达、管理水平高的大城市推广,而青岛市模式更适合在人口规模较小、商业保险机构独立承办风险较大、监管能力较弱的城市实行。     

人骨唾液蛋白非融合荧光蛋白载体的构建及在乳腺癌细胞中的表达

背景：人骨唾液蛋白基因在矿化组织以外的易发生骨转移的人乳腺癌中表达。临床观察显示骨转移处的乳腺癌细胞骨唾液蛋白的表达量要高于原发部位的乳腺癌细胞，因此骨唾液蛋白有可能与肿瘤特异性骨转移的关系密切。研究乳腺癌骨转移可为将来临床的预防和治疗提供新的药物靶点。目的：建立骨唾液蛋白的稳定表达乳腺癌细胞系，观察骨唾液蛋白在乳腺癌骨转移的整个过程中的作用。设计：对照实验。单位：华南理工大学生物科学与工程学院，解放军广州军区广州总医院医学实验中心。材料：实验于2003-11／2004-03在解放军广州军区广州总医院医学实验室完成。质粒、菌种和细胞：pIRES2-EGFP载体质粒，E．Coli．Top10、含有人骨唾液蛋白基因全长的克隆载体pB-hBSP和发生特异性骨转移以及脑转移的人乳腺癌细胞株MDA-MB-231BO和MDA-MB-23lBR。方法：将人骨唾液蛋白基因通过聚合酶链式反应的方法从构建好的pB-hBSP载体中亚克隆出来，在其5’和3’端分别引入BglⅡ和PsiⅠ限制性酶切位点，定向克隆至真核表达载体pIRES2-EGFP，构建重组载体pIRES2-hBSP-EGFP。利用脂质体转染的方法将构建好的重组质粒转入特异性脑转移和骨转移的乳腺癌细胞株MDA-MB-231BR和MDA-MB-231BO中。主要观察指标：pIRES2-hBSP-EGFP重组表达载体的构建。重组表达载体pIRES2-hBSP-EGFP转染乳腺癌细胞。结果：①成功构建人骨唾液蛋白和绿色荧光蛋白非融合表达的真核表达载体pIRES2-hBSP-EGFP。②成功转染特异骨转移和脑转移的乳腺癌细胞株，可在荧光显微镜下观察到荧光蛋白标记，人骨唾液蛋白得到相应表达。结论：真核表达载体pIRES2-hBSP-EGFP的构建及转染可为骨唾液蛋白在乳腺癌骨转移中的作用的体内、外研究奠定一定的基础。     

Oligomeric proanthocyanidins alleviate hexabromocyclododecane-induced cytotoxicity in HepG2 cells through regulation on ROS formation and mitochondrial pathway

Hexabromocyclododecane (HBCD), a type of brominated flame retardants (BFR), has become ubiquitous organic contaminants in recent years. However, studies on HBCD toxicity and the related molecular mechanisms are so far limited. The objective of the present study was to investigate the effects of oligomeric proanthocyanidins (OPCs) on cytotoxicity induced by HBCD and the underlying molecular mechanisms. HepG2 cells were treated with HBCD and/or OPCs at different concentrations, and cell viability, cell apoptosis, reactive oxygen species (ROS) production, cellular Ca²⁺ level, mitochondrial membrane potential (ΔΨ), cytochrome C (Cyt-c) release, and nuclear factor-erythroid 2-related factor 2 (Nrf2) proteins expression were evaluated. Results showed that HBCD induced toxic effects in HepG2 cells in a concentration-dependent manner. HBCD at high concentrations (40 and 60 μM) caused a significant decrease of cell viability and led to elevated cell apoptosis ratio, intracellular Ca²⁺ level, cytoplasmic Cyt-c level, and ROS production, together with a loss of ΔΨ and mobilization of Nrf2. Pretreatment with OPCs effectively attenuated the cytotoxic effects and ROS production, as well as mitochondrial responses induced by HBCD. Thus, OPCs could alleviate cytotoxicity in HepG2 cells induced by HBCD through regulation on intracellular Ca²⁺ level and ROS formation in a mitochondrial pathway.     

广东阳江产仙人草挥发油化学成分研究

采用超声波辅助水蒸气蒸馏方法提取阳江产仙人草（Mesona chinensis Benth）中的挥发油,用气相色谱-质谱（GC-MS）方法对其成分进行分析鉴定。实验结果说明,从挥发油中分离和鉴定出37种成分,占总峰面积的90.20%。其中含有丰富的对人体健康有益的化学成分,如O-丁子香酚、n-棕榈酸、alpha-毕橙茄醇、反式-石竹烯、石竹烯氧化物等,含量均在5%以上。     

An Experimental Study on the Dynamic Mechanical Properties of Epoxy Polymer Concrete under Ultraviolet Aging

Epoxy polymer concrete (EPC) is widely applied in engineering for its excellent mechanical properties. The impact loads and severe climatic conditions such as ultraviolet radiation, temperature change and rain erosion are in general for its engineering practice, potentially degrading the performance of EPC. In this paper, a procedure of accelerated aging for EPC, imitating the aging effect of ultraviolet radiation and hygrothermal conditions based on the meteorological statistics of Guangzhou city, was designed. After various periods of accelerated aging, the dynamic behaviors of EPC were studied by using a Split Hopkinson Pressure Bar (SHPB). The verification of the experimental data was performed. The two-stage dynamic compression stress-strain curves were obtained: (a) linear growth stage following by strain hardening stage at impact velocity 12.2 m/s and 18.8 m/s, (b) linear growth stage and then a horizontal stage when impact velocity is 25.0 m/s, (c) linear growth stage following by strain softening stage at impact velocity 29.2 m/s. The experimental results show that the specimens after longer accelerated aging tend to be more easily broken, especially at impact velocity 12.2 m/s and 18.8 m/s, while the strain rate is the main factor affecting the compression strength and stiffness. Ultimately the influence of strain rate and equivalent aging time on dynamic increase factor was revealed by a fitting surface.     

In-Situ Synthesis,Microstructure, and Mechanical Properties of TiB2-Reinforced Fe-Cr-Mn-Al Steel Matrix Composites Prepared by Spark Plasma Sintering

In-situ synthesis, microstructure, and mechanical properties of four TiB₂-Reinforced Fe-Cr-Mn-Al Steel Matrix Composites have been researched in this work. The microstructure and phases of the prepared specimens have been characterized by using scanning electron microscopy (SEM), X-ray diffraction technique, and transmission electron microscopy (TEM). The sintered specimens consisted of Fe₂AlCr, CrFeB-type boride, and TiB₂. The mechanical properties, such as hardness and compression strength at room temperature (RT) and at elevated temperatures (600 °C and 800 °C) have been evaluated. The compressive strength and Vickers hardness of the sintered specimens increase with the volume fraction of TiB₂ in the matrix, which are all much higher than those of the ex-situ TiB₂/Fe-15Cr-20Mn-8Al composites and the reported TiB₂/Fe-Cr composites with the same volume fraction of TiB₂. The highest Vickers hardness and compressive strength at room temperature are 1213 ± 35 HV and 3500 ± 20 MPa, respectively. As the testing temperature increases to 600 °C, or even 800 °C, these composites still show relatively high compressive strength. Precipitation strengthening of CrFeB and in-situ synthesis of TiB₂ as well as nanocrystalline microstructure produced by the combination of mechanical alloying (MA) and spark plasma sintering (SPS) can account for the high Vickers hardness and compressive strength.