GC-MS Analysis and Microbiological Evaluation of Caraway Essential Oil as a Virulence Attenuating Agent against Pseudomonas aeruginosa

The emergence of resistant microbes threatens public health on our planet, and the emergence of resistant bacteria against the most commonly used antibiotics necessitates urgent alternative therapeutic options. One way to fight resistant microbes is to design new antimicrobial agents, however, this approach takes decades of research. An alternative or parallel approach is to target the virulence of bacteria with natural or synthetic agents. Active constituents from medicinal plants represent a wide library to screen for natural anti-virulence agents. Caraway is used as a traditional spice and in some medicinal applications such as carminative, antispasmodic, appetizer, and expectorant. Caraway essential oil is rich in terpenes that were previously reported to have antimicrobial activities. In our study, we tested the caraway essential oil in sub-inhibitory concentration as a virulence agent against the Gram-negative bacteria Pseudomonas aeruginosa. Caraway essential oil in sub-inhibitory concentration dramatically blocked protease activity, pyocyanin production, biofilm formation, and quorum sensing activity of P. aeruginosa. The gas chromatography–mass spectroscopy (GC-MS) profile of caraway fruit oil identified 13 compounds representing 85.4% of the total oil components with carvone and sylvestrene as the main constituents. In conclusion, caraway essential oil is a promising virulence-attenuating agent that can be used against topical infections caused by P. aeruginosa.     

含三苯胺单元的超支化共轭聚合物的合成、表征及应用

本实验采用Wittig方法制得了未封端和封端的超支化聚三苯胺-对苯乙烯撑型聚合物,对两种共轭聚合物进行了表征和性能测试.聚合物溶液和固体膜在紫外光照射下均发出较强的绿光.首次对这类聚合物在硝基芳烃化合物荧光猝灭能力进行了初步研究,结果表明:与未封端产物相比,封端后的超支化共轭聚合物在邻硝基甲苯(o-NT)的荧光猝灭效率上有明显提高,当o-NT浓度为21.5×10^-3mol/L时,荧光猝灭效率达到97%.这类共轭聚合物不仅合成操作较为简便,猝灭效率也较高,是一种很有潜力的硝基芳烃化合物荧光检测材料.     

穿心莲提取物与牛血清白蛋白相互作用的研究

以芦丁(rutin)为对照品,测定了穿心莲提取物中总黄酮的含量.采用荧光光谱(三维荧光、时间驱动模式)和紫外-可见吸收光谱研究了穿心莲提取物与牛血清白蛋白(BSA)间的相互作用,讨论了药物对BSA构象的影响,证实了二者间相互作用为单一的动态猝灭过程,求出了猝灭常数Ksv=0.95 × 103,并依据能量转移理论确定了药物与蛋白的最近距离r=2.15 nm.     

一种分子内电荷转移荧光探针与牛血清白蛋白相互作用的研究

应用荧光光谱法研究了分子内电荷转移荧光探针1-酮-2-(对二甲氨基苯亚甲基)-四氢萘(KDTN)与牛血清白蛋白(BSA)的相互作用。研究表明,KDTN能与牛血清白蛋白形成稳定的络合物从而猝灭BSA的荧光,疏水作用是结合反应的主要作用力,二者的结合常数为3.274 2×104 L·mol-1,结合位点数n=0.938 9(30 ℃时)。同时考察了KDTN的加入对BSA构象的影响。     

酸度对氧氟沙星与牛血清白蛋白结合的影响

牛血清白蛋白在不同pH的溶液中存在N（pH ～7.0）,B（pH ～9.0）和E（pH 3.5以下）等几种同分异构形态。 采用紫外-可见光谱和荧光光谱研究了酸度对牛血清白蛋白（BSA）的结构以及对不同结构的BSA和氧氟沙星的相互作用的影响,应用荧光猝灭现象和Frster理论,求出了4个不同pH下两者结合的猝灭常数、 能量转移效率和结合距离等参数。结果显示,氧氟沙星与牛血清白蛋白在pH 4.9时结合常数最大（1.928 1×105 L·mol-1）,结合距离小（r=2.55 nm）,猝灭效应最好（8.63×104 L·mol-1）;氧氟沙星与牛血清白蛋白的结合过程中,静态猝灭和非辐射能量转移是导致牛血清白蛋白荧光猝灭的原因;中性、 弱酸和弱碱性环境对两者的结合没有太大的影响,静电作用不是两者相互作用的主要作用力。使用同步荧光技术考察了氧氟沙星对BSA构象的影响。     

荧光光谱法研究二溴羟基卟啉与蛋白质的结合作用机理

应用荧光光谱法研究了meso-四(3,5-二溴-4-羟基苯基)卟啉[T(DBHP)P]与牛血清白蛋白(BSA)之间的结合反应,基于T(DBHP)P对BSA内源荧光的猝灭机理,测定了两者之间在不同温度下的结合常数,温度为27 ℃时,荧光猝灭法测得反应的结合常数为K=1.30×106 L·mol-1,温度为48 ℃时,K=6.32×105 L·mol-1,结合常数随温度升高而减小,由此判定该猝灭类型为静态猝灭。根据Frster非辐射能量转移理论,确定了T(DBHP)P与BSA之间的能量转移效率E=0.91,能量给体(BSA)与受体[T(DBHP)P]之间的结合距离r=2.39 nm<7 nm,符合非辐射能量转移条件。依据热力学参数ΔG<0,ΔH<0,ΔS>0确定了T(DBHP)P与BSA之间的作用力主要是静电引力。同时,利用同步荧光光谱,考察了T(DBHP)P对BSA构象的影响,结果发现,T(DBHP)P的加入使BSA构象发生变化,BSA内部残基所处环境的疏水性降低。     

罗丹明6G荧光猝灭法测定农产品中痕量铁

在稀硫酸溶液中,铁(Ⅲ)与碘化钾反应生成游离碘(以络阴离I-,3 状态存在).所释出的I-,3与罗丹明6G反应生成离子缔合络合物,导致罗丹明 6G 的荧光猝灭.在激发波长 483 nm 及发射波长 551 nm 处测定空白试液及含铁试样溶液的荧光强度F,o及F,s并算得荧光猝灭强度△F.试验结果表明:铁(Ⅲ)的质量浓度在 0.01～0.40 mg·L-1范围内与其相应的荧光猝灭值△F 之问呈线性关系,并测得其检出限(S/N=3)为 0.005 mg·L-1.应用此方法测定了3种农产品试样中的含铁量,并以此试样为基体加入铁(Ⅲ)标准溶液测定了方法的回收率在 95.7%～99.3%之间.     

水杨基荧光酮荧光猝灭法测定茶叶中微量钼

在HCI介质中.吐温80(Tween80)存在下.钼与水杨基荧光酮(SAF)形成复杂配合物使荧光熄灭.由此建立了测定微量钼的荧光熄灭新方法.该体系的最大激发波长λex=365mm,最大发射波长λex =518mm.Mo(Ⅵ)含量在0-25 ug/25mL范围荧光熄灭程度(△F)与Mo(Ⅵ)浓度呈线性关系,线性回归方程为△F=24/4c(ug/25mL)-0.246.相关系数R2=0.9995,检出限为1.32ug/L.该方法灵敏度高,选择性好,用于测定茶叶中的微量钼,回收率在98.2%~100.3%之间,结果令人满意.     

Substrate effects on photophysical properties of fluorescent self‐assembled monolayers (SAMs)

Substrate materials play an important role to modulate the photophysical properties of fluorescent self‐assembled monolayers (SAMs) constructed on them. The substrate–fluorophore interactions in fluorescent SAMs can affect their fluorescence intensity. Hence, it is important to take into account such alteration of fluorescence properties and study the underlying mechanisms. In this brief overview, substrate effects on fluorescence properties of chemisorbed or physisorbed fluorescent SAMs on two‐dimensional (chips) and three‐dimensional (nanoparticles) surfaces are highlighted. Examples of fluorescence quenching and enhancement on various substrate materials by different factors are discussed and analyzed. Additionally, some strategies to limit metallic substrate–fluorophore interactions are discussed briefly. Copyright © 2016 John Wiley & Sons, Ltd.     

Novel isoindigo‐based conjugated polyelectrolytes: Synthesis and fluorescence quenching behavior with water‐soluble poly(p‐phenylenevinylene)s

Two novel ID‐based water‐soluble conjugated polymers (+)‐PIDPV and (?)‐PIDPV were synthesized by Heck coupling reaction. These two polyelectrolytes are both consisted of isoindigo units and phenylenevinylene units. In the UV–vis absorption spectra, both (+)‐PIDPV and (?)‐PIDPV exhibit broad absorption bands that almost cover the whole visible region. Photophysical investigations reveal that the fluorescence of water‐soluble PPV can be efficiently quenched by oppositely charged PIDPV at a very low concentration. Cationic PPV shows an efficient quenching effect with Κ_SV = 1.01 × 10⁶ M^?1 in the presence of (?)‐PIDPV while the anionic PPV gives a lager quenching constant with Κ_SV = 1.71 × 10⁶ M^?1 in the presence of (+)‐PIDPV. Furthermore, the blend films of water‐soluble PPVs and oppositely charged PIDPV also exhibit excellent quenching effect. These properties suggest that (+)‐PIDPV and (?)‐PIDPV are promising materials in the application of ionic photoactive layer in the organic solar cells. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2223–2237