基于离子选择性电极的硝酸盐快速检测系统

介绍了一种用于快速检测溶液中硝酸盐含量的流体控制系统。系统选用自主研发的以聚吡咯聚合物为膜材料的硝酸盐离子选择性电极作为传感单元,通过底层数据采集器编程控制微型泵和微型阀,实现检测溶液的自动传输控制。根据流体控制流程,离子选择性电极的标定溶液浓度选择为10-1、10-3和10-4 mol/L,标定时间可控制在4.5 min以内,每个样品检测时间为90 s。在10-4～10-1 mol/L的硝酸盐浓度范围内,电极的电势响应斜率值相对稳定,系统的硝酸盐含量检测下限约为10-4 mol/L,可基本满足对土壤浸提溶液和生活饮用水硝酸盐含量的快速和低成本检测要求。     

Effect of Polarity of Complexing Agents on Thermal and Rheological Properties of Rice Starch Gels

The ability of rice starch to complex with ligands of various polarities was studied to examine the mechanism of complex formation in an aqueous solution. Differential scanning calorimetry (DSC) showed that TNuS19 rice starch (27.9% amylose) formed inclusion complexes with all 12-C complexing agents. The onset melting temperatures (T_o) of the complexes were ≈93–96°C. The saturation concentrations of added ligands with high polarity, lauric acid (LA), and lauryl alcohol (LOH), had a range of 2–4% (w/w) of the starch, and both of the corresponding melting enthalpies (ΔH) were ≈3.0 J/g. In contrast, the saturation concentrations of ligands with low polarity, methyl laurate (ML) and dodecane (DO), were ≈1–2% (w/w), and the ΔH were 1.87 and 1.80 J/g, respectively. This implied that solubility of ligands had a significant effect on the extent of complexation. The T_o and ΔH increased with an increase of annealing time at 85°C, and the optima for the partially reversible complex formation were 2 hr of annealing in all cases. When measured by a dynamic rheometer, the TNuS19 rice starch gel with added LA or LOH showed a higher storage modulus (G′) than that with no complexing agent added during heating. The G′ and tan δ of the complexed gel were further increased during 12 hr of storage. The increase of G′ indicated that the elastic structure of the concentrated rice starch gels could be improved by complex formation and annealing, whereas the increase of tan δ suggested incompatibility of starch components during storage.     

Cu^2＋Zn^2＋和Cd^2＋对5种单细胞藻类生长的影响

报道承Ｃｕ＾２＋Ｚｎ＾２＋和Ｃｄ＾２＋的毒性作用下,三角褐指藻、湛江叉鞭藻、路氏巴夫藻、青岛大扁藻和小球藻等单细胞藻类的生长速度,密度都发生了不同程度的变化,叉鞭、扁藻及巴夫藻易中毒且恢复慢,当金属离子浓度较低时生长仍然缓慢。而小球藻和三角褐指藻耐毒能力较强,在２００×１０＾－６,甚至６００×１０＾－６离子浓度下仍可生长 。     

Pressurized water extraction of polysaccharides as secondary metabolites from Lentinula edodes

The suitability of pressurized water extraction (PWE) of crude polysaccharides as secondary metabolites from Lentinula edodes was investigated. A series of experiments were carried out to examine the effects of extraction times and pressures. The results indicated that the maximum recovery of polysaccharides was about 90% of the crude polysaccharides from mycelia pellets when the pressure was at 10.1 MPa for 70 min (28 degrees C). This was a drastic improvement over that of boiling water extraction (BWE) at 0.1 MPa for 40 min, which gave only 27.9% recovery. A nitroblue tetrazolium (NBT) reduction assay was used to examine the macrophage stimulating activities (MSA), and it was found that the PWE polysaccharides retained the MSA. The morphology of the macrophage cells treated by PWE polysaccharides was also examined and found to be similar to that of the positive control lipopolysaccharides treated. Finally, gel chromatographic and NMR experiments revealed that both PWE and BWE polysaccharides showed the presence of four similar molecular mass components and the alpha-(1-->4)-D-Glcp and beta-(1-->6)-D-Glcp linkage residues. The improved PWE efficiency is probably due to the possibility that under high pressure, the solid polysaccharide's hydrogen bonding is partially destroyed to increase structure elasticity and water solubility.     

Resveratrol content in strawberry fruit is affected by preharvest conditions

This study investigated the occurrence of resveratrol in Fragaria x ananassa Duchesne and the effect of preharvest conditions on resveratrol content. Both cis- and trans-resveratrol were detected in strawberry achenes (seeds) and pulp (receptacle tissue). Resveratrol was found to be higher in achenes than in fruit pulp. The levels of resveratrol were affected by genotype variations, fruit maturation, cultural practices, and environmental conditions. High growing temperature (25 and 30 degrees C) or enriched CO 2 in the atmosphere significantly enhanced resveratrol content of strawberries. Advancing maturation also increased resveratrol content. The mature pulp and achenes contained higher amounts of resveratrol than the immature fruit. Adding compost as a soil supplement or preharvest application of methyl jasmonate (MJ) also significantly enhanced the level of resveratrol in strawberry fruit. Among the plants grown in hill plasticulture, fruits of 'Ovation (B28)', 'Mohawwk', 'Earliglow', and 'B35' had higher amounts of resveratrol than fruits of other genotypes. 'Ovation' contained the highest amount of resveratrol among strawberries grown in matted row, whereas 'Latestar' contained the least. Ten of 14 tested genotypes (all except 'Allstar', 'Delmarvel', 'Northeaster', and 'MEUS 8') had higher amounts of resveratrol when grown in hill plasticulture compared to matted row.     

Mechanisms underlying Actinobacillus pleuropneumoniae exotoxin ApxI induced expression of IL-1β, IL-8 and TNF-α in porcine alveolar macrophages

ABSTRACT: Actinobacillus pleuropneumoniae (A. pleuropneumoniae) causes fibrino-hemorrhagic necrotizing pleuropneumonia in pigs. Production of proinflammatory mediators in the lungs is an important feature of A. pleuropneumoniae infection. However, bacterial components other than lipopolysaccharide involved in this process remain unidentified. The goals of this study were to determine the role of A. pleuropneumoniae exotoxin ApxI in cytokine induction and to delineate the underlying mechanisms. Using real-time quantitative PCR analysis, we found native ApxI stimulated porcine alveolar macrophages (PAMs) to transcribe mRNAs of IL-1β, IL-8 and TNF-α in a concentration- and time-dependent manner. Heat-inactivation or pre-incubation of ApxI with a neutralizing antiserum attenuated ApxI bioactivity to induce cytokine gene expression. The secretion of IL-1β, IL-8 and TNF-α protein from PAMs stimulated with ApxI was also confirmed by quantitative ELISA. In delineating the underlying signaling pathways contributing to cytokine expression, we observed mitogen-activated protein kinases (MAPKs) p38 and cJun NH2-terminal kinase (JNK) were activated upon ApxI stimulation. Administration of an inhibitor specific to p38 or JNK resulted in varying degrees of attenuation on ApxI-induced cytokine expression, suggesting the differential regulatory roles of p38 and JNK in IL-1β, IL-8 and TNF-α production. Further, pre-incubation of PAMs with a CD18-blocking antibody prior to ApxI stimulation significantly reduced the activation of p38 and JNK, and subsequent expression of IL-1β, IL-8 or TNF-α gene, indicating a pivotal role of β2 integrins in the ApxI-mediated effect. Collectively, this study demonstrated ApxI induces gene expression of IL-1β, IL-8 and TNF-α in PAMs that involves β2 integrins and downstream MAPKs.     

Polarization-modulated smectic liquid crystal phases

Any polar-ordered material with a spatially uniform polarization field is internally frustrated: The symmetry-required local preference for polarization is to be nonuniform, i.e., to be locally bouquet-like or "splayed." However, it is impossible to achieve splay of a preferred sign everywhere in space unless appropriate defects are introduced into the field. Typically, in materials like ferroelectric crystals or liquid crystals, such defects are not thermally stable, so that the local preference is globally frustrated and the polarization field remains uniform. Here, we report a class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves. The polar domains are locally chiral, and organized into patterns of alternating handedness and polarity. The fluid-layer undulations enable an extraordinary menagerie of filament and planar structures that identify such phases.     

Hemoglobin J-Korat in Thais

Hemoglobin J(Korat), a "fast" hemoglobin with an anomaly in its beta chain different from the anomalies previously reported, was the major hemoglobin component in the blood of nine subjects among 1923 Thais from northeastern Thailand. After hemoglobin E, J(Korat) is the second most frequent of the anomalous hemoglobins among Thais.     

Modified atmosphere packaging alleviates chilling injury in cucumbers

Cucumbers (Cucumis sativus L.) packaged in perforated or sealed 31.75 μm (1.25 mil) low density polyethylene (LDPE) bags were found to have less severe chilling injury than nonwrapped fruit in storage at 5 °C and 90–95% relative humidity. The onset of chilling injury was also delayed by the LDPE packaging compared to the nonpackaged control. The concentrations of CO₂ increased to 3% while O₂ levels decreased to 16% in the sealed bags. Fruit in the sealed bags had the least decay. The O₂ and CO₂ concentrations inside the perforated bags changed very little from the ambient atmosphere. However, there was a marked difference in the weight loss between nonwrapped cucumbers and fruit from perforated or sealed bags. The weight loss of nonwrapped fruit reached 9% in 18 days while perforated and sealed samples lost less than 1% during the same period. Chilling stress induced increases in putrescine levels in all treatments but the sealed fruit had the highest levels of putrescine. Sealed fruit and perforated fruit also had higher content of spermidine than non-wrapped fruit. These high levels of polyamines may have contributed to the increase of chilling tolerance in fruit from perforated and sealed packages.