Fiber-optic chlorine probe based on fluorescence decay of N-(6-methoxyquinolyl)acetoethyl ester

A fiber-optic probe for measuring chlorine in aqueous solution is evaluated. The probe uses a microporous gas-permeable membrane to trap a small volume of aqueous internal solution made of N-(6-methoxyquinolyl)acetoethyl ester (MQAE) in front of a fiber-optic assembly. The working principle of this probe is based on a combination of fluorescence quenching and redox reaction of MQAE by chloride ion and chlorine, respectively. While the magnitude of total fluorescence decay is independent of the sample concentration, the initial rate of decrease in fluorescence intensity is linearly proportional to the chlorine concentration over the range from 8.4 to 418 microM. Once the probe is exposed to a chlorine sample, the probe tip must be refilled with a fresh aliquot of the internal solution before the next measurement. In this mode, the probe displays excellent reproducibility; the relative standard deviation of the initial rate of fluorescence decay (n = 3) is only 1 percent. This probe can also be used for the measurement of hypochlorous acid (HOCl) in aqueous solution. The response properties are identical to those of the chlorine probe.     

席夫碱共价有机框架的合成及对I ‒ 的识别

设计合成了一种新型共价有机框架类荧光探针TpPa-COOH COF, 该探针在THF/H₂O(体积比1∶1)混合溶液中能够高选择性识别I^?. 向体系中加入I^?后, 溶液由浅红色变为黄色, 317 nm处荧光强度明显降低. 该探针具有良好的选择性, 抗干扰能力强, 检出限为0.028 μmol/L, pH适用范围广(1~13), 具有良好的应用前景.     

一种2-乙酰基吡嗪-罗丹明B衍生物的合成及其对Ni~(2+)的识别

分子光谱法具有灵敏度高、操作简单等优点,发展简便、快捷、对镍离子(Ni~(2+))具有高度选择性的探针具有非常重要的意义。本文以金属离子诱导罗丹明酰胺衍生物反应开环的策略,设计并合成了对Ni~(2+)检测具有单一选择性识别的紫外吸收探针。同时,该探针可对水溶液中的Ni~(2+)实现"裸眼"识别。此外,该探针对Ni~(2+)具有较高的灵敏度,其对水溶液中Ni~(2+)的检测限为0.5μmol/L,表明该探针可用于Ni~(2+)的检测分析。     

A fluorescent probe for monitoring nitric oxide production using a novel detection concept

A fluorescent probe using a novel 'spin exchange' concept was developed for monitoring nitric oxide (NO) production. The probe is composed of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) labeled with acridine and N-dithiocarboxysarcosine (DTCS)-Fe(II) complex. When the non-fluorescent acridine-TEMPO was incubated with DTCS-Fe(II) complex in buffer solution, the nitroxide radical in the acridine-TEMPO interacted with the Fe(II) through a redox interaction. This interaction recovered the fluorescence based on the acridine moiety. The addition of an NO-releasing reagent caused a fluorescent decrease of the probe due to the irreversible binding of NO to the Fe(II), and the amount of the fluorescent decrease strictly corresponded to that of released NO. Using this probe, less than 100 nM of NO can be detected. This probe system is not only useful for monitoring direct production of NO in an aqueous solution, but is also interesting as a basic concept by which to construct new types of NO fluorescent probes.     

Fluorescent Polypyrrole Nanospheres – Synthesis and Properties of “Wireless” Redox Probes

In this work a novel concept of monitoring of occurrence of redox reactions between conducting polymer nanospheres and redox species in a solution is proposed. The redox process is monitored in the emission mode (without wiring of the probe to an electrochemical measuring set‐up) as a change in emission spectrum of a dye (not participating in the redox process itself) but reporting the alteration of properties of highly sensitive conducting polymer nanoparticles. This approach is possible due to applied unique method of synthesis of conducting polymers nanospheres of highly active, unblocked surface. Thus the nanospheres redox state is affected by the solution redox potential, leading to change of their properties. If solvatochromic probe of sufficiently high brightness (pyrene) is present in nanospheres, a redox reaction between the conducting polymer and solution can be observed as change of emission spectrum of the probe. Thus a localized redox potential optical probe can be obtained. The emission properties of the dye incorporated were preserved in the nanospheres, moreover, the emission spectrum of the probe was affected by the change in redox potential of the solution, thus influencing the redox state and ultimately the properties of the conducting polymer. The emission changes observed were dependent on ion‐exchange properties of polypyrrole, i.e. depending on the dopant ions present in the polymer, the sensitivity of the optical probe can be tuned.     

一种检测肼的纳米粒子探针及其生物成像应用

肼是一种广泛使用的化工原料,但它也是一种有毒化学品,对人类健康和环境安全有着严重威胁。因此,开发一种方便、快速检测肼的方法具有重要的意义。本文制备了一种芘甲醛纳米粒子探针,其能和肼快速反应,从而使探针的荧光信号发生变化,实现对肼的荧光检测。该探针检测肼具有高选择性和灵敏度,并成功地应用于HeLa细胞和斑马鱼中肼的成像。     

A fluorescent probe directly detect peroxynitrite based on boronate oxidation and its applications for fluorescence imaging in living cells

We present the design, synthesis, spectroscopy, and biological applications of PyBor, a new type of fluorescent probe for peroxynitrite detection in aqueous solution and living cells. The probe employs pyrene as the fluorophore, and is equipped with a chemically responsive unit boronate. The fluorescent probe can selectively detect peroxynitrite with fluorimetric determination and high-performance liquid chromatography analyses in aqueous solution and RAW264.7 cells intracellular free extracts. We also study our probe to time dependent peroxynitrite release from 3-morpholinylsydnonimine hydrochloride. Confocal microscopy experiments using mouse macrophage cell line RAW264.7 show that PyBor is able to detect the different intracellular peroxynitrite levels. In addition, we have performed quantum chemical calculations with TD-DFT/M06/TZVP level with COSMO solvation model basis sets using a suite of Gaussian 09 programs to provide insights into the structure optical properties of PyBor and PyOH.     

Binary malachite green aptamer for fluorescent detection of nucleic acids

A new probe that can fluorescently report the presence of specific nucleic acids in solution with extremely high selectivity was developed. The probe consists of malachite green-a triphenylmethane dye-and two short RNA strands, each of which comprises a fragment complementary to an analyte molecule and a fragment of a malachite green aptamer (MGA). The two RNA strands form MGA upon hybridization to the adjacent positions of the nucleic acid analyte. MGA is able to bind malachite green and enhance the fluorescence of the dye, thus monitoring the presence of the nucleic acid in solution. The probe reliably discriminates against 41 out of 42 possible single nucleotide substitutions in 14-mer DNA analyte at room temperature in physiological buffer. Consisting of unmodified RNA strands, which can be expressed in living cells, binary MGA probe represents a promising instrument for real-time nucleic acid monitoring in vivo.     

Application of porous metal enrichment probe sampling to single cell analysis using matrix‐assisted laser desorption ionization time of flight mass spectrometry (MALDI‐TOF‐MS)

There is an increasing need for analyzing metabolism in a single cell, which is important to understand the nature of cellular heterogeneity, disease, growth and specialization, etc. However, single cell analysis is often challenging for the traces of samples. In the present study, porous metal enrichment probe sampling combined with matrix‐assisted laser desorption ionization time of flight mass spectrometry ( MALDI‐TOF‐MS) has been applied for in situ analysis of live onion epidemic cell. Porous probe, treated by corroding copper wire with HCl, was directly inserted into a single cell to get cell solution. A self‐made linear actuator was enough to control the penetration of probe into the target cell accurately. Then samples on the tip of probe were eluted and detected by a commercial MALDI‐TOF‐MS directly. The formation of porous microstructure on the probe surface increased the adsorptive capacity of cell solution. The sensitivity of porous probe sampling was 6 times higher than uncorroded probes generally. This method provides a sensitive and convenient way for the sampling and detection of single cell solution. Copyright © 2015 John Wiley & Sons, Ltd.     

一种Fe3+荧光探针的合成及其检测性能研究

金属离子的高效检测对于人类健康和环境保护极其重要。本文通过对甲基苯磺酸催化下3-脱氢莽草酸甲酯与若丹明6G乙二胺缩合的芳构化反应合成了一种检测Fe~(3+)的荧光探针分子Rh M606。该探针分子在乙醇溶液中特异性地与Fe~(3+)络合,导致若丹明内酰胺开环,在553nm处出现强的荧光发射峰。该荧光探针对Fe~(3+)具有良好的选择性,可定量检测水中的Fe~(3+),检测限为3. 93μmol/L。     

利用荧光探针研究水溶性高分子溶液的结构

利用荧光探针技术研究水溶性高分子在溶液中的构象转变近年来引起了广泛的注意^[1-3]。这不仅是由于水溶性高聚物的实际应用日益增多,而且它还可能作为某种生化模拟体系,为研究了解复杂的生化体系提供有用资料。     

A "reactive" ratiometric fluorescent probe for mercury species

A ratiometric fluorescent probe for mercury species is developed based on the metal-promoted hydrolysis of a vinyl ether derivative of 2-(benzothiazol-2-yl)phenol in a buffer solution. The probe responds selectively to mercury species over various other metal ions with a marked fluorescence change from blue to cyan through the excited state intramolecular proton transfer (ESIPT) process. The fluorescence titration is complete with 0.5 equiv of HgCl(2), which indicates that the probe also responds to organomercury species, RHgCl.     

Performance of an ion trap mass spectrometer modified to accept a direct insertion membrane probe in analysis of low level pollutants in water

Modifications to a Finnigan ITS40 ion trap mass spectrometer are described which allow its use with a direct insertion probe. Details are given of the fabrication of a membrane probe for such an instrument. The membrane probe, which includes facilities for heating the fluid, employs a tubular membrane which is located just outside the electrode structure of the ion trap. Direct analysis of organic compounds in aqueous solution is demonstrated using a silicone membrane, with compounds such as benzene, chlorobenzene and dichloroethene being studied below the 1 ppb level. The effects of operating parameters including probe temperature, ion trap temperature, solution flow rate, mass spectrometer scan speed, and instrument tune procedures are explored in detail. Optimum performance characteristics are identified and trace level detection of eight organic compounds in the parts per trillion range is demonstrated. In seven of the eight cases studied, detection limits are below the EPA practical limit of quantitation levels. It is shown that the most sensitive mode of operation is when steady state passage of the analyte across the membrane is achieved, however, the time required for this is long in the case of some samples, and a dynamic flow injection analysis procedure is then favored. Use of the modified inlet system for solid sample introduction via a standard solids probe is also demonstrated.     

UV spectroscopy of DNA duplex and quadruplex structures in the gas phase

UV absorption spectroscopy is one of the most widely used methods to monitor nucleic acid folding in solution, but the absorption readout is the weighted average contribution of all species present in solution. Mass spectrometry, on the other hand, is able to separate constituents of the solution based on their mass, but methods to probe the structure of each constituent are needed. Here, we explored whether gas-phase UV spectroscopy can give an indication of DNA folding in ions isolated by electrospray mass spectrometry. Model DNA single strands, duplexes, and G-quadruplexes were extracted from solution by electrospray; the anions were stored in a quadrupole ion trap and irradiated by a tunable laser to obtain the UV action spectra of each complex. We found that the duplex and quadruplex spectra are significantly different from the spectra of single strands, thereby suggesting that electronic spectroscopy can be used to probe the DNA gas-phase structure and obtain information about the intrinsic properties of high-order DNA structure.     

Sensitive and enzyme-free detection for single nucleotide polymorphism using microbead-assisted toehold-mediated strand displacement reaction

This report described a free-enzyme, convenient and inexpensive genotyping biosensor capable of detecting single nucleotide polymorphism at normal temperature based on the combination of toeholdmediated strand displacement reaction(toehold-SDR) and microbead-capture technique. The biosensor consists of a pre-hybridized strand formed by a reporter probe and a capture probe. In the presence of a mutant sequence, there is no toehold-mediated strand displacement and the reporter probe cannot be released from the pre-hybridized strand. Microbeads capture the fluorescent pre-hybridized strand through biotin–streptavidin interaction, so microbeads give out significant fluorescence signal, while there is no fluorescence in the solution. However, in the presence of a matched target, the strand displacement is effectively initiated and the reporter probe is released from pre-hybridized strand. After adding microbeads, the solution produces bright fluorescence, while microbeads have no obvious signal.Genotypes are identified conveniently according to the fluorescence intensity of the solution. The method provides a simple and inexpensive strategy to detect point mutation. Moreover, this biosensor shows the linear relationship in the range of 1–40 nmol/L and reaches a detection limit of 0.3 nmol/L.     

Tethered thiazole orange intercalating dye for development of fibre-optic nucleic acid biosensors

Single-stranded DNA (ssDNA) oligonucleotide in solution, or that is immobilized onto a surface to create a biosensor, can be used as a selective probe to bind to a complementary single-stranded sequence. Fluorescence enhancement of thiazole orange (TO) occurs when the dye intercalates into double-stranded DNA (dsDNA). TO dye has been covalently attached to probe oligonucleotides (homopolymer and mixed base 10mer and 20mer) through the 5′ terminal phosphate group using polyethylene glycol linker. The tethered TO dye was able to intercalate when dsDNA formed in solution, and also at fused silica surfaces using immobilized ssDNA. The results indicated the potential for development of a self-contained biosensor where the fluorescent label was available as part of the immobilized oligonucleotide probe chemistry. The approach was shown to be able to operate in a reversible manner for multiple cycles of detection of targeted DNA sequences.     

A sensitive fluorescence anisotropy method for detection of lead (II) ion by a G-quadruplex-inducible DNA aptamer

Sensitive and selective detection of Pb²⁺ is of great importance to both human health and environmental protection. Here we propose a novel fluorescence anisotropy (FA) approach for sensing Pb²⁺ in homogeneous solution by a G-rich thrombin binding aptamer (TBA). The TBA labeled with 6-carboxytetramethylrhodamine (TMR) at the seventh thymine nucleotide was used as a fluorescent probe for signaling Pb²⁺. It was found that the aptamer probe had a high FA in the absence of Pb²⁺. This is because the rotation of TMR is restricted by intramolecular interaction with the adjacent guanine bases, which results in photoinduced electron transfer (PET). When the aptamer probe binds to Pb²⁺ to form G-quadruplex, the intramolecular interaction should be eliminated, resulting in faster rotation of the fluorophore TMR in solution. Therefore, FA of aptamer probe is expected to decrease significantly upon binding to Pb²⁺. Indeed, we observed a decrease in FA of aptamer probe upon Pb²⁺ binding. Circular dichroism, fluorescence spectra, and fluorescence lifetime measurement were used to verify the reliability and reasonability of the sensing mechanism. By monitoring the FA change of the aptamer probe, we were able to real-time detect binding between the TBA probe and Pb²⁺. Moreover, the aptamer probe was exploited as a recognition element for quantification of Pb²⁺ in homogeneous solution. The change in FA showed a linear response to Pb²⁺ from 10 nM to 2.0 μM, with 1.0 nM limit of detection. In addition, this sensing system exhibited good selectivity for Pb²⁺ over other metal ions. The method is simple, quick and inherits the advantages of aptamer and FA.     

一种近红外花菁染料的合成及其应用于生物大分子的测定

光谱性质;蛋白质;核酸测定;一种近红外花菁染料的合成及其应用于生物大分子的测定     

Current measurements within the electrospray emitter

A movable disc-like wire probe electrode placed inside the electrospray (ES) capillary was used to measure currents flowing within the ES device for the first time. Currents were measured between the wire probe and the ES capillary. Current maps revealing measured current versus wire probe position were generated for a variety of solution conditions in the positive and negative ion modes and are compared to potential maps. The electrospray device was found to subsist on highly stable total currents; this current regulator aspect of the ES device showed remarkable resiliency regardless of the proportion of current produced at the wire probe electrode versus the ES capillary. However, kinks observed in the current and potential maps are attributed to adsorbed air participating in electrochemical reactions, and turbulence in solution flow in the region of the Taylor cone. From differential electrospray emitter potential (DEEP) maps, current maps, and cyclic voltammetry experiments performed at different wire probe locations, evidence is provided for separate regimes of current flow in the bulk solution and in the thin "skin" of highly conductive electrolyte constituting the outer surface (air interface) of the Taylor cone. Current maps reveal that current is drawn more evenly along the length of the ES capillary when solutions are highly conductive, in agreement with previous results for DEEP maps. In less conductive solutions, the area close to the capillary exit contributes more heavily to current production. Evidence that contaminant participation in electrochemical processes occurring within the electrospray device can be largely responsible for production of the excess charge in ES droplets is also provided. These investigations complement previous DEEP mapping studies to further elucidate the details of the electrochemical processes occurring within the electrospray device.     

一种基于喹唑啉酮衍生物的荧光探针对次氯酸根离子的识别

次氯酸根(ClO~-)在人体免疫系统中发挥着重要的作用,其识别与检测备受关注。本文设计合成了一种含有喹唑啉酮骨架的腙型荧光探针(HEMQ),并通过~1H NMR、~(13)C NMR、高分辨质谱(HRMS)表征了其结构。探针HEMQ在V(乙醇)∶V(水)=1∶1(c(PBS)=0.02 mol/L,pH=8.7)溶液中对ClO~-具有良好的选择性且响应快速,荧光发生显著猝灭。探针HEMQ对ClO~-具有较高的灵敏度,检测限为1.0×10-4mol/L。此外,ClO~-可引起探针溶液由黄色到无色的颜色变化,因此HEMQ可作为比色、荧光双通道响应的ClO~-探针。