A Highly Selective and Sensitive Ratiometric Fluorescent Probe for pH Measurement Based on Fluorescence Resonance Energy Transfer

Fluorescein-rhodamine 6G(Flu-Rh) was synthesized and used as the fluorescence probe for pH measurement based on fluorescence resonance energy transfer(FRET). In the probe, fluorescein fluorophore and pH-sensitive rhodamine 6G hydrazide were used as FRET donor and acceptor, respectively. The values of acidity constant(pK_a) and fluorescence quantum yield(Φ) of Flu-Rh were 3.71 and 0.72, respectively. The fluorescence efficiency of Flu-Rh remains almost constant when the pH value of the sample solution changed 10 times in a range of 4.78-7.03 continuously. The present probe is simple and easy-to-use for the pH measurement in acidic media.     

Fluorescein-derived fluorescent probe for cellular hydrogen sulfide imaging

In this work, a fluorescein-derived fluorescent probe for H2 S based on the thiolysis of dinitrophenyl ether is reported. This probe exhibits turn-on fluorescence imaging of H2 S in living cells and bulk solutions with excellent selectivity. The reaction mechanism was explained by means of absorption, fluorescence and HPLC–MS.     

Hypervalent iodine oxidation of benzil-α-arylimino oximes: an efficient synthesis of 2,3-diphenylquinoxaline-1-oxides

A mild and efficient synthetic protocol for the oxidation of benzil-α-arylimino oximes 3 utilizing iodobenzene diacetate (IBD) as an oxidizing agent has been developed. Oximes 3, obtained by the condensation of (E)-benzil monoxime 2 with various appropriately substituted anilines 1, on treatment with iodobenzene diacetate in dichloromethane at room temperature underwent oxidative cyclization to afford 2,3-diphenylquinoxaline-1-oxide 4 in excellent yields.     

Homogeneous indirect fluorescence quenching immunoassay for the determination of low molecular weight substances

This paper describes the principle of a homogeneous indirect fluorescence quenching immunoassay that uses monoclonal antibodies. It is a carrier-free assay system that is performed completely in solution. The assay system was established for the determination of a low molecular weight substance (hapten), the herbicide diuron, used as a model analyte. A fluorescein–monuron conjugate together with a fluorescence-quenching monoclonal anti-fluorescein antibody and an anti-analyte antibody (here an anti-diuron/monuron monoclonal antibody) were used as central components of the assay. The fluorescein–monuron conjugate can be bound either by the anti-fluorescein monoclonal antibody or by the anti-diuron/monuron monoclonal antibody. Due to steric hindrance, binding of both antibodies to the conjugate was not possible at the same time. By selecting the antibody concentrations appropriately, a dynamic equilibrium can be established that permits the preferential binding of the anti-diuron/monuron antibody to the conjugate, which allows the fluorescein in the conjugate to fluoresce. This equilibrium can be easily altered by adding free analyte (diuron), which competes with the conjugate to bind to the anti-diuron/monuron antibody. A reduction of anti-diuron/monuron antibody binding to the conjugate results in an increase in the binding of the anti-fluorescein antibody, which leads to a decrease in the fluorescence of the conjugate. The fluorescence is therefore a direct indicator of the state of equilibrium of the system and thus also the presence of free unconjugated analyte. The determination of an analyte based on this test principle does not require any washing steps. After the test components are mixed, the dynamic equilibrium is rapidly reached and the results can be obtained in less than 5 min by measuring the fluorescence of the fluorescein. We used this test principle for the determination of diuron, which was demonstrated for concentrations of ∼5 nM.     

二醋酸纤维素-离子液体膜固定肌红蛋白制备过氧化氢传感器

将二醋酸纤维素(CDA)-(1-丁基-3-甲基咪唑四氟硼酸盐离子液体)([bmim]BF4)-肌红蛋白(Mb)的复合物修饰在玻碳电极(GCE)表面,制备了一种新型Mb修饰电极(CDA-[bmim]BF4-Mb/GCE).光谱分析表明:固定在CDA- [bmim]BF4-Mb膜中的肌红蛋白保持了其天然构象和生物活性.离子...     

A ‘turn-on’ fluorescent sensor for the selective detection of cobalt and nickel ions in aqueous media

Two newly designed turn-on fluorescein-based chemosensors are highly sensitive and selective for Co²⁺ and Ni²⁺ in both absorption and emission modes, normally difficult to achieve with these paramagnetic ions. Binding to both ions is reversible, as indicated by the bleaching of the color when the metal is extracted with EDTA. Given the difficulty of designing enhanced fluorescent sensors for paramagnetic Co²⁺ and Ni²⁺ ions, the fluorescein compounds may inspire the further development of more sophisticated sensing constructs for the detection of these ions.     

醋酸纤维素／聚乙烯基吡咯烷酮共混体系的相容性研究（Ⅰ）

用ＤＳＣ，ＤＭＴＡ研究了醋酸纤维素（ＣＤＡ），聚乙烯基吮咯烷酮（ＰＶＰ）及ＣＤＡ／ＰＶＰ共混体系的玻璃化转变行为．用精密量热法测定了该体系的混合热焓．结果表明：共混体系只存在一个玻璃化转变温度（Ｔｇ），其值随共混组成的变化而改变；共混体系的混合热焓为负值，其绝对值随组成中ＰＶＰ含量的增加而减少．力学性能研究表明，共混体系具有协同效应．上述试验结果证明，ＣＤＡ和ＰＶＰ是一对相容性高聚物．     

FITC标记重组灵芝免疫调节蛋白(rLz-8)在NB4细胞中的动态定位

实验发现, 重组灵芝免疫调节蛋白(rLz-8)可直接杀伤人急性早幼粒细胞白血病细胞株NB4. 利用异硫氰酸荧光素(FITC)标记rLz-8, 其相关的活性实验结果和晶体结构分析都表明, FITC没有影响rLz-8已知生物学功能. 通过激光共聚焦显微镜观察FITC-rLz-8在NB4细胞内的动态过程发现, FITC-rLz-8可识别细胞膜上的受体, 并可进入细胞质, 并最终富集在细胞核区域内. Annexin V-FITC双染检测结果显示, rLz-8对NB4细胞杀伤作用的可能机制是对NB4细胞凋亡的诱导作用, 在一定浓度范围内, 剂量与凋亡诱导率成正相关. 因此rLz-8能够诱导肿瘤细胞NB4发生凋亡的亚细胞学机制可定位在细胞核上.     

汞灯光源芯片毛细管电泳荧光电荷耦合器件检测系统

以宽谱带高压汞灯为光源的倒置荧光显微镜,配备电荷耦合器件(CCD)及微流控芯片,自组装芯片毛细管电泳荧光电荷耦合器件检测系统。选择不同激发波长(340~540 nm)荧光试剂,进行荧光检测,荧光素的检出限(S/N=3)为7.3×10-9mol/L,荧光素异硫氰酸酯(FITC)的检出限(S/N=3)为1.7×10-8mol/L,显示了该系统对荧光试剂选择范围宽、灵敏度高的特点。用该系统成功分离了FITC与荧光素、曙红与荧光素两种混合荧光试剂。实验表明,组装的芯片毛细管电泳CCD荧光检测系统是成功的。     

各种荧光素酯-蒽甲酸酯的光电性能研究

Fluorescein ethyl ester as a model and four dyads of Fluorescein and Anthroic acid linked with different length spacer were synthesized and characterized. They were put in bilayer membrane and on SnO2 coated substrate, The photoinduced voltaic responses were observed and compared when fluorescein was excited using visible light. It was found that the dyads have higher responses than the model, and the dyad with a butylene spacer (n=4) has the highest response. The results and related mechanisms were discussed.