Determination of environmentally important metal ions by fluorescence quenching in anionic micellar solution

This work describes the effect of a variety of metal ions as quenchers of the fluorescence of naphthalene, in aqueous micellar solutions of sodium dodecyl sulfate (SDS). The quenching by the metal ions can be adequately described by the Stern-Volmer equation and the best signal to noise ratios are obtained with low micellized detergent concentrations. Apparent Stern-Volmer constants decrease in the order: Fe3+ > Cu2+ > Pb2+ > Cr3+ > Ni2+ and directly reflect the relative sensitivity of the method for these ions. Detection limits (defined as three times the standard deviation of the blank for n= 10) for the fluorescence quenching of naphthalene by the metal ions in aqueous micellar SDS are in the range of 1.0 x 10(-6) to 1.0 x 10(-5) mol dm(-3). The proposed fluorescence quenching method shows good repeatibility for a variety of added quencher metal ions, indicating that anionic micelle-enhanced fluorescence quenching by metal ions constitutes an analytical method of rather general application.     

Appearance of pure fluorocarbon micelles surveyed by fluorescence quenching of amphiphilic quinoline derivatives in fluorocarbon and hydrocarbon surfactant mixtures

A halide-sensitive fluorescence probe was utilized to evaluate the miscibility of fluorocarbon and hydrocarbon surfactants in aqueous micellar systems. The fluorescence of 6-methoxy-N-1,1,2,2-tetrahydroheptadecafluorodecylquinolinium chloride, FC10MQ, was quenched by halide ions dissociated from the surfactant. The fluorescence in micellar solutions showed an initially rapid decay. This suggests that halide ions effectively quench FC10MQ fluorescence at the micellar surface. The subsequent slow decay corresponds to the quenching of FC10MQ fluorescence in the aqueous bulk phase by the free counterions. The Stern-Volmer plots for fluorescence quenching gave a distinct break at the critical micelle concentration of the cationic surfactants. The abrupt increase in fluorescence quenching is attributed to the solubilization of the probe in the micelles. The fluorescence quenching behavior provides direct information about the immiscibility of fluorocarbon and hydrocarbon species in micelles, and the results indicate that almost pure fluorocarbon micelles appear in surfactants mixtures.     

表面活性剂胶束化过程中对芘的荧光猝灭

本文研究了烷基三苯基 盐及N-烷基吡啶盐胶束化过程中对芘的荧光猝灭。讨论了表面活性剂分子在水溶液中的优势构型以及芘在胶束中的增溶位置。简单说明了胶束增敏发光分析的机理。研究表明,胶束形成前后荧光猝灭均符合Stern-Volmer方程。     

Fluorescence Quenching of 1-Pyrenemethanol by Methylviologen in Polystyrene Latex Dispersions

Fluorescence quenching of 1-pyrenemethanol by methylviologen through photoinduced electron transfer is investigated in polystyrene (PS) latex dispersions as well as in aqueous homogeneous solutions. In aqueous homogeneous solutions, the Stern-Volmer plot for the intensity is linear and close to that for the lifetime, indicating a dynamic quenching mechanism. In PS latex dispersions, however, the Stern-Volmer plots for the intensity are downward curving and the decay curves are not so much affected by the quencher as those for aqueous solutions, implying a significant contribution of static quenching. The downward-curving Stern-Volmer plots are well described by a two-site model that assumes accessible and inaccessible sites to the acceptor on latex particles. The Stern-Volmer constants obtained indicate that in the latex dispersions the fluorescence quenching occurs several hundreds times more efficiently than that in an aqueous homogeneous solution. This drastic enhancement of the quenching in latex dispersions is attributed to the increase in the local concentrations of the reactants on the latex surface. We have demonstrated the usefulness of latex surfaces as a new type of reaction field for photoinduced electron transfer.     

Electronic Spectroscopic Study of the Formation of a Molecular Complex Between Asphaltene and o-Chloranil in SDS Aqueous Micellar Medium

Ultraviolet-visible absorption and steady-state fluorescence of asphaltene in sodium dodecyl sulphate (SDS) micellar medium containing o-chloranil have been studied. Spectroscopic results indicate formation of a complex between asphaltene and o-chloranil. The absorption spectrum of the complex has been detected by difference spectral method. The position of maximum absorption of the complex in micellar medium agrees well with that of the complex in the carbon tetrachloride medium studied previously. The formation constant (K) has been determined using Benesi-Hildebrand equation utilizing absorption spectral data. Formation of ground state complex involving asphaltene and o-chloranil has also been evidenced from the study of quenching of asphaltene fluorescence by o-chloranil. The value of K, as obtained by Stern-Volmer plot, agrees well with that obtained by absorption spectrophotometric method.     

Fluorescence quenching of TMR by guanosine in oligonucleotides

Nucleotide-specific fluorescence quenching in fluorescently labeled DNA has many applications in biotechnology. We have studied the inter- and intra-molecular quenching of tetramethylrhodamine (TMR) by nucleotides to better understand their quenching mechanism and influencing factors. In agreement with previous work, dGMP can effectively quench TMR, while the quenching of TMR by other nucleotides is negligible. The Stern-Volmer plot between TMR and dGMP delivers a bimolecular quenching constant of K _s = 52.3 M⁻¹. The fluorescence of TMR in labeled oligonucleotides decreases efficiently through photoinduced electron transfer by guanosine. The quenching rate constant between TMR and guanosine was measured using fluorescence correlation spectroscopy (FCS). In addition, our data show that the steric hindrance by bases around guanosine has significant effect on the G-quenching. The availability of these data should be useful in designing fluorescent oligonucleotides and understanding the G-quenching process.     

Anomalous association and fluorophore influence on the position of dimethylaniline in micelles: fluorescence quenching of 1,8-acridinedione

Fluorescence quenching of 9,10-dimethyl-3, 4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione (ADD) dye by N,N-dimethylaniline (DMA) in SDS and CTAB were studied by steady state fluorescence and time resolved techniques. The Stern-Volmer plots for the quenching of ADD by DMA is found to be linear and the Stern-Volmer constant K(SV) depends on the micellar concentration. The fluorescence quenching analysis reveals the binding of DMA with the micelles. The perturbation of the probe on the position of DMA molecule in micelle is inferred in the present investigation. The ADD fluorophore drives the DMA molecule into the non-polar region (core) of the micelle whereas other fluorophores like pyrene and rhodamine6G do not affect the position of DMA. In this report, the importance of the nature of fluorophores in determining the position and association of the quencher molecules in the aggregated systems is being discussed.     

甲苯咪唑与牛血清白蛋白作用的荧光光谱特征

用荧光光谱法研究了甲苯咪唑与牛血清白蛋白结合反应的光谱特征，证实由于非辐射能量转换机制，甲苯咪唑对牛血清白蛋白有较强的荧光猝灭能力，按照Stem—Volmer方程和双倒数方程分析处理实验数据，得到反应的结合常量和热力学参数等。     

Fluorescence resonance energy transfer from tryptophan in human serum albumin to a bioactive indoloquinolizine system

The interaction between a bioactive molecule, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), with human serum albumin (HSA) has been studied using steady-state absorption and fluorescence techniques. A 1:1 complex formation has been established and the binding constant (K) and free energy change for the process have been reported. The AODIQ-HSA complex results in fluorescence resonance energy transfer (FRET) from the tryptophan moiety of HSA to the probe. The critical energy-transfer distance (R ₀) for FRET and the Stern-Volmer constant (K _sv) for the fluorescence quenching of the donor in the presence of the acceptor have been determined. Importantly, K _SV has been shown to be equal to the binding constant itself, implying that the fluorescence quenching arises only from the FRET process. The study suggests that the donor and the acceptor are bound to the same protein at different locations but within the quenching distance.     

寡聚核苷酸中鸟苷对四甲基罗丹明的荧光猝灭

具有核苷特异性的荧光猝灭技术在生物领域具有广泛应用.为了更好地理解这一过程的机理及其影响因素,研究了核苷对四甲基罗丹明（TMR）染料的分子间猝灭和在同一条寡聚核苷酸链中的分子内猝灭.与以前的研究结果一致,脱氧单磷酸鸟苷（dGMP）可以有效地猝灭TMR,而其他单磷酸腺苷对其的猝灭可以忽略.由斯特恩-沃尔默图获得TMR和dGMP的双分子猝灭常数为Ks=52.3L/mol.将TMR标记在寡聚核苷酸末端,可以观测到其荧光通过光致电子传递有效地被鸟苷猝灭,我们利用荧光相关光谱的方法测定了这一过程的猝灭速率常数.此外,所得的数据还显示鸟苷附近的碱基会对分子内的猝灭过程产生显著的位阻效应.这些结果将有助于设计寡聚核苷酸荧光探针和理解G猝灭过程.     

Fluorescence quenching of anthracene by indole derivatives in phospholipid bilayers

The quenching of anthracene fluorescence by indole, 1,2-dimethylindole (DMI), tryptophan (Trp) and indole 3-acetic acid (IAA) in palmitoyloleoylphosphatidylcholine (POPC) lipid bilayers was investigated. A very efficient quenching of the anthracene fluorescence in the lipid membrane is observed. Stern-Volmer plots are linear for DMI but present a downward curvature for the other quenchers. This was interpreted as an indication of the presence of an inaccessible fraction of anthracene molecules. By a modified Stern-Volmer analysis the fraction accessible to the quenchers and the quenching constant were determined. The changes in the fluorescence emission spectrum of indole and DMI have been used to calculate the partition constants of these probes into the membranes, and bimolecular quenching rate constants were determined in terms of the local concentration of quencher in the lipid bilayer. The rate constants are lower than those in homogeneous solvents, which may be ascribed to a higher viscosity of the bilayer. No changes in the emission spectra of Trp and IAA are observed in the presence of vesicles, indicating that these probes locate preferentially in the aqueous phase, or in close proximity to the vesicular external interface in a medium resembling pure water. In these cases quenching rate constants were determined in terms of the analytical concentration. In the quenching by DMI a new, red shifted, emission band appears; it is similar to that observed in non-polar solvents and it is ascribable to an exciplex emission. The exciplex band is absent in the quenching by IAA and Trp and only very weakly present when the quencher is indole. From the position of the maximum of the exciplex emission, a relatively high local polarity could be estimated for the region of the bilayer where the quenching reaction takes place.     

荧光光谱法研究注射用头孢美唑钠与牛血清白蛋白的相互作用

运用荧光光谱法研究了注射用头孢美唑钠(Cefmetazole Sodium,CS)与牛血清白蛋白(BSA)的相互作用.CS对BSA具有荧光猝灭作用,其猝灭方式为静态猝灭,求出了猝灭常数,结合常数及结合位点数.在297 K和311 K时用Stern-Volmer方程和热力学方程处理实验数据,得到了结合常数KA、热力学参数...     

卤代荧光素荧光猝灭法测定肾上腺色腙

在pH=6.6 的缓冲介质中, 肾上腺色腙(CBZC)与二氯荧光素(DCF)、二溴荧光素(DBF) 和二碘荧光素(DIF)通过静电引力、芳基堆积作用和范德华力形成摩尔比为2: 1的复合物, 引起上述二卤代荧光素的荧光发生猝灭, 最大猝灭波长分别位于533, 536和560 nm. 其荧光猝灭值(ΔF)在一定范围内与肾上腺色腙浓度成正比, 荧光猝灭反应具有较高的灵敏度, 对CBZC的检出限分别为3.3 ng/mL(CBZC-DCF体系), 5.7 ng/mL(CBZC-DBF体系)和129.6 ng/mL(CBZC-DIF体系). 考察了共存物质的影响、荧光猝灭反应的适宜条件和影响因素, 结果表明, 该方法具有良好的选择性, 可用于CBZC的血药和尿药浓度的快速检测. 从温度的影响、荧光寿命以及Stern-Volmer图判断该反应为静态猝灭反应.     

Fluorescence quenching of coumarins by halide ions

Fluorescence quenching of 4-methyl-7-methoxy coumarin (1) and 4-methyl-5-ethoxy-7-methoxy coumarin (2) in aqueous solutions have been studied at different concentrations of halide ions (Cl-, Br-, I-), at room temperature approximately 20 degrees C. It is observed that the fluorescence intensity of both the coumarin compounds (1 and 2) decrease with increase in the concentration of Br- and I- ions but remains almost constant in case of Cl- ion. It is observed that the quenching due to halide ions proceeds via both a diffusional and static quenching processes. The rate constants for diffusional as well as static component of quenching process have been calculated using modified Stern-Volmer relation. It is further observed, that I- ion has very high quenching ability than Br- ion and Cl) ion almost behaves as a non-quencher. It is explained in terms of the sphere of action model by showing that the value of radius of sphere of action of the halide quencher is greater than the sum of the radii of the respective coumarin and quencher. Further, pattern of the quenching ability of the halide quenchers is found to be as I- > Br- > Cl- and interestingly this is in the same order as of their ionization energy. Finally, the present quenching process has been attributed to the electron transfer resulting between colliding species.     

Tryptophan Modification and Fluorescence Spectrum of Hyaluronidase

Tryptophan residues in hyaluronidase （HAase） were modified by N-bromosuccinimide （NBS）, the results indicated that there were eleven tryptophan residues in HAase, one of which was exposed and essential for the activity of the enzyme. The study on fluorescence quenching showed that KI could not quench all of the fluorescence from Trp residues in HAase, while acrylamide （Acr） could quench almost all of the fluorescence from Trp residues in HAase. The collisional quenching constants （KD） of HAase at different concentrations of Acr were calculated in terms of Stern-Volmer equation. The results implied that some of the Trp residues were buried in the interior of HAase and the Trp residue on the surface of HAase was not located in the hydrophobic pocket.     

Fluorescence Energy Transfer Study of Interstrand DNA Cross-linking Caused by Rigid Bisintercalator

The intermolecular cross-linking of DNA with a rigid bisintercalator, 1,4-bis(( N -methylquinolinium-4-yl)vinyl)benzene (pMQVB) has been studied using fluorescence resonance energy transfer (FRET), fluorescence anisotropy measurements, and dynamic fluorescence microscopy. Short DNA duplexes, single-labeled with fluorescein (donor) and x-rhodamine (acceptor), were used as energy transfer partners. Due to the quenching effect of pMQVB on the emission of both fluorescein and x-rhodamine, the energy transfer was monitored using the corrected Stern-Volmer plots. The cross-linking ability of pMQVB depended on the ligand structure; the planar E , E isomer cross-linked DNA contrary to the non-planar E , Z isomer. Dynamic fluorescence microscopy observation also demonstrated the ability of pMQVB to cross-link large T4 DNA molecules.     

VARIATION OF STERN-VOLMER QUENCHING CONSTANTS IN MICELLAR SOLUTION AS A FUNCTION OF AQUEOUS OR MICELLAR QUENCHER

Abstract— The critical micelle concentration (CMC) of a fluorescent detergent may be measured by determining Stern-Volmer quenching parameters as a function of detergent concentration. The CMC's of a cationic detergent, 11-(3-hexyl-l-indolyI)undecyltrimethylamrnoniurn bromide (6-In-ll+), and an anionic detergent, sodium H-(3-hexyI-l-indoiyI) undecyl sulfate (6-In-ll⁻) were determined by this quenching procedure. Quenchers which were predominantly located in the aqueous phase (e.g. Co²+) or in the micellar phase (e.g. benzophenone) were employed. Aqueous phase quenchers are more effective below the CMC and cause a decrease in the long wavelength portion of the fluorescence band of the indole moiety. Quenchers located in the micellar phase are more effective above the CMC and decrease the short wavelength portion of the fluorescence band of the system.     

Fluorescence chemosensors with pyrene and their interaction with nucleotide phosphate

A group of fluorescence chemosensor with pyrene, compounds (Ⅰ), (Ⅱ) and (Ⅲ), were synthesized The fluorescence spectra and the lifetime of these compounds were carefully measured. The fluorescence quenching spec tra of pyrenyl butyric acid, compounds (Ⅰ), (Ⅱ) and (Ⅲ) by different nucleotide phosphates, AMP ADP, ATP dTTP, were also recorded and studied. The quenching and the stability constants were calculated by Stern-Volmer equa tion and eq. (2), respectively. The mechanism of interaction between fluorescence chemosensor and nucleotide phos phate was didscussed based on the comparison of the results obtained with the CPK model of free molecules of these com pounds in the ground state.     

荧光猝灭方法研究腺苷酸衍生物与嘧啶碱的弱相互作用──Stern-Volmer方程在竞争吸收体系中的修正式

已知在液氮温度下(77 K)核酸碱基之间能生成基态复合物^[1],这些复合物的荧光发射有比较大的红移.在室温条件下,核酸碱基的荧光发射量子产率很低,以至几乎无法检测.     

Interaction of Zinc Oxide and Copper Oxide Nanoparticles with Chlorophyll: A Fluorescence Quenching Study

The present study aims to investigate the interactions of zinc oxide nanoparticles and copper oxide nanoparticles with the major photosynthetic pigment chlorophyll using ultraviolet-visible, steady state, and time resolved laser induced fluorescence spectroscopy. The steady state fluorescence measurements show that zinc oxide and copper oxide nanoparticles quench the fluorescence of chlorophyll in concentration-dependent manner. The Stern-Volmer plot for the chlorophyll-zinc oxide nanoparticles is linear, and the value of quenching constant has been observed to increase with temperature indicating the possibility of dynamic quenching. A decrease in the lifetime of chlorophyll with increase in the concentration of zinc oxide nanoparticles confirms the involvement of dynamic quenching in the chlorophyll–zinc oxide nanoparticle interaction. In the case of copper oxide nanoparticles, the Stern-Volmer plot deviates from linearity observed in the form of upward curvature depicting the presence of both static and dynamic quenching. In addition, the lifetime of chlorophyll decreases with increase in the concentration of copper oxide nanoparticles displaying the dominance of dynamic quenching in the chlorophyll-copper oxide nanoparticle interaction. The decrease observed in the value of binding constant with increasing temperature and negative values of change in enthalpy, entropy, and Gibb’s free energy indicates that van der Waal and hydrogen bonding are the prominent forces during the interaction of chlorophyll with both zinc oxide and copper oxide nanoparticles and that the process is spontaneous and exothermic. The interaction of zinc oxide and copper oxide nanoparticles with chlorophyll occurs through electron transfer mechanism. The obtained results are useful in understanding the sensitization processes involving chlorophyll and zinc oxide and copper oxide nanoparticles.