β-Carotene Inhibits Expression of Matrix Metalloproteinase-10 and Invasion in Helicobacter pylori-Infected Gastric Epithelial Cells

Matrix metalloproteinases (MMPs), key molecules of cancer invasion and metastasis, degrade the extracellular matrix and cell–cell adhesion molecules. MMP-10 plays a crucial role in Helicobacter pylori-induced cell-invasion. The mitogen-activated protein kinase (MAPK) signaling pathway, which activates activator protein-1 (AP-1), is known to mediate MMP expression. Infection with H. pylori, a Gram-negative bacterium, is associated with gastric cancer development. A toxic factor induced by H. pylori infection is reactive oxygen species (ROS), which activate MAPK signaling in gastric epithelial cells. Peroxisome proliferator-activated receptor γ (PPAR-γ) mediates the expression of antioxidant enzymes including catalase. β-Carotene, a red-orange pigment, exerts antioxidant and anti-inflammatory properties. We aimed to investigate whether β-carotene inhibits H. pylori-induced MMP expression and cell invasion in gastric epithelial AGS (gastric adenocarcinoma) cells. We found that H. pylori induced MMP-10 expression and increased cell invasion via the activation of MAPKs and AP-1 in gastric epithelial cells. Specific inhibitors of MAPKs suppressed H. pylori-induced MMP-10 expression, suggesting that H. pylori induces MMP-10 expression through MAPKs. β-Carotene inhibited the H. pylori-induced activation of MAPKs and AP-1, expression of MMP-10, and cell invasion. Additionally, it promoted the expression of PPAR-γ and catalase, which reduced ROS levels in H. pylori-infected cells. In conclusion, β-carotene exerts an inhibitory effect on MAPK-mediated MMP-10 expression and cell invasion by increasing PPAR-γ-mediated catalase expression and reducing ROS levels in H. pylori-infected gastric epithelial cells.     

PSMA@Ag复合微球的制备及其在MALDI-MS分析小分子化合物中的应用研究

基质辅助激光解吸电离质谱(MALDI-MS)作为一种有力的分析手段,在生物分子分析中有着广泛的应用,但很难应用于分子量小于500的待测物的分析。该文利用聚多巴胺修饰还原法制备了核壳结构的聚苯乙烯-马来酸酐共聚物@银纳米壳层(PSMA@Ag)复合微球。采用傅立叶红外光谱法验证了聚多巴胺(PDA)的成功修饰。结合扫描电子显微镜(SEM)和紫外-可见光谱(UV-Vis)分析结果,发现Ag纳米壳层成功地包覆在PSMA微球的表面。将制备的PSMA@Ag复合微球作为辅助基质直接应用于MALDI-MS,成功地从0.5μL待测物样品中检测到2 pmol脯氨酸(M_w=115)和1 pmol丝氨酸(M_w=105)。研究结果证明PSMA@Ag微球对MALDI的离子化过程有促进作用,为解决MALDI-MS在分析小分子待测物时背景噪声过大,信号无法分辨的问题提供了一个有效途径。     

电感耦合等离子体原子发射光谱(ICP-AES)法测定锡精矿中8种杂质元素

应用电感耦合等离子体原子发射光谱(ICP-AES)法同时测定锡精矿中钙、镁、铜、铅、锌、砷、锑、铋8种杂质元素。对锡精矿样品的分解方法进行了合理选择,并对测定时的元素分析谱线、基体及各测定元素间干扰情况等进行了讨论。采用硝酸、盐酸、氢氟酸、高氯酸溶样,盐酸浸取。基体效应较小,各待测元素之间基本无干扰。测定结果与国家标准方法比对结果基本一致,相对标准偏差为1.3%~3.3%(n=11),方法加标回收率为96.0%~105%,能满足实际工作中准确、高效地分析锡精矿中杂质元素的需要。     

液相色谱-串联质谱法测定蜂产品中吡虫啉及其3种代谢物

建立了蜂蜜和蜂花粉中吡虫啉及其代谢物吡虫啉烯烃、吡虫啉脲、6-氯烟酸的液相色谱-串联质谱(LC-MS/MS)检测方法.在QuEChERS方法基础上,针对目标物化学性质和样品杂质情况,对提取溶液的pH值、提取次数、净化材料等参数进行了优化.最终以5％甲酸-乙腈溶液提取两次,无水MgSO4、NaCl盐析分层,提取液经增强型脂类去除材料(EMR)净化,以LC-MS/MS进行测定,基质外标法进行定量分析.结果表明,蜂蜜和蜂花粉中吡虫啉、吡虫啉烯烃、吡虫啉脲、6-氯烟酸的平均加标回收率为86.0％～111.5％, 相对标准偏差在1.7％～9.6％之间, 检出限分别为0.20, 3.50, 0.40和14.00 μg/kg,定量限分别为0.60, 11.64, 1.20和45.00 μg/kg.本方法分析速度快、灵敏度高、重现性好,适用于蜂蜜和蜂花粉中吡虫啉及其3种代谢物的快速测定.     

基质辅助激光解析/电离飞行时间质谱(MALDI-TOF MS)在微生物鉴定中的应用*

基质辅助激光解析/电离飞行时间质谱(MALDI-TOF MS)是一种新型软电离生物质谱,具有检测速度快、操作简便、结果准确等优点,目前已成为可靠的微生物快速鉴定技术。就工作流程而言,与常规生化方法相比,MALDI-TOF MS可以将微生物鉴定的时间缩短为一天甚至更短。对于具有抗生素耐药性的微生物,使用MALDI-TOF MS鉴定也有很好的准确性。在病毒鉴定中,MALDI-TOF MS也可以发挥作用,已有报道将MALDI-TOF MS和机器学习(ML)分析方法结合来检测鼻拭子中SARS-CoV-2。此外,MALDI-TOF MS还可用于细菌的无光谱库鉴定。目前,MALDI-TOF MS正通过与其他技术(例如傅里叶红外光谱FTIR)相结合进一步扩大微生物鉴定范围。     

Zeolitic imidazolate framework-8 as a dispersive solid phase extraction sorbent for simultaneous determination of 145 pesticide residues in polyphenol-rich plants

Many plants have a high polyphenol content, which causes the matrix effect and makes the analysis of trace pesticide residues highly challenging. A common approach to improving matrix effects is to purify pesticides through the use of sorbents, but this requires a combination of multiple sorbents and extensive use. Zeolitic imidazolate framework-8 is widely used for pesticide analysis due to its high porosity, large specific surface area, and versatility. Here, we established and validated a modified quick, easy, cheap, effective, rugged, and safe method based on a zeolitic imidazolate framework-8 that was used to test the removal ability for polyphenols. To this end, 145 pesticide residues in peppermint, perilla, fennel, and mulberry leaves were analyzed by the modified method coupled with liquid chromatography with tandem mass spectrometry. The mean recoveries of all pesticide residues were in the range of 74.3–103.7%, with mean relative standard deviations ≤9.1% at spiked concentrations of 1, 10, 50, and 100 μg/kg for mulberry leaves. The limits of quantitation of the method ranged from 1 to 50 μg/kg. This study offers a reliable approach for the accurate quantitative analysis of various trace substances in the polyphenol-rich plants.     

振型归一化对梁结构柔度曲率损伤指标的影响

结构柔度矩阵需由质量矩阵归一化振型获得,而质量矩阵归一化振型难以直接测得,限制了柔度曲率类损伤指标的应用。为分析振型归一化方法对梁结构柔度曲率类损伤指标的影响,根据梁结构的刚度、弯矩和位移曲率的关系,建立了均布荷载作用下结构损伤前后位移曲率与损伤程度的理论表达式,实现定量分析均匀荷载面曲率结构损伤程度。提出P-范数振型归一化方法,通过均匀荷载面曲率指标推导了振型质量矩阵归一化系数差x_α与损伤程度的关系。以三跨连续梁算例对理论进行了验证,结果表明,损伤程度定量指标效果良好,不同P-范数振型归一化方法下,损伤程度的偏差可由2x_α估算;2-范数振型归一化方法的损伤识别结果与质量矩阵振型归一化结果最接近,故当无法获得质量矩阵归一化振型时,可采用2-范数归一化振型代替。     

延性单晶非均匀变形的三维有限元模拟

对延性单晶在拉伸载荷作用下的应变局域化和颈缩等非均匀变形过程进行了三维有限元数值模拟。将相关晶体塑性本构模型及一种新的数值积分方法补充到ABAQUS6.1商用有限元软件中。该方法的特点是，利用晶体塑性的动力学方程，获得一个关于晶体弹性变形梯度的演化方程，采用半隐式积分方案进行求解。本文推导出一种新的应力变本构矩阵。按此方式更新本构矩阵，计算速度和计算稳定性大大提高。加载方式，边界条件和变形程度等因素影响着滑移系的启动状况，这是平面模型所不能预测的。本文利用三维有限元方法模拟了不同取向下滑移系的启动状况，全面地考虑了FCC单晶材料12个可能滑移系在变形过程中的启动状况，合理地模拟了FCC面心立方单晶沿不同取向加载时晶轴旋转导致的应变局域化和颈缩等非均匀变形过程。     

任意非亏损矩阵特征灵敏度分析的模态展开法

把特征向量的各阶导数表示成所有模态的线性组合，并利用左模态与右模态间的双正交性，首先导出了任意非亏损矩阵的重特征值的一阶导数所满足的特征值问题，然后根据此特征值问题无、看重根的情况，再导出了异导重特征值和等导重特征值对应的可微特征向量、特征值和特征向量各阶导数的一般计算公式。算例显示了方法的正确性。     

高温磨损中合金组成体的作用及其相互依赖

作者用其自制的高温磨损试验机考察了不同含碳量的Fe-Cr及Fe-Cr-Mn合金的高温耐磨性。通过数据分析及磨损面和亚表层之结构和组织的观察,论述了共晶碳化物及金属基体在高温磨损条件下对材料耐磨性的贡献和相互依赖性。作者指出,高硬度共晶碳化物在高温磨损过程中能够发挥一定的抵抗磨料的作用而使合金的耐磨性提高;基体组织在高温时的塑性变形是影响合金高温耐磨性的一个重要因素,它直接影响共晶碳化物发挥抵抗磨料作用的程度;Fe-Cr-Mn合金中由于Mn的加入改善了基体组织的性能,使其硬度和高温耐磨性均比Fe-Cr合金的高。