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At least 559 records · Page 31Linked to original sources
PubMed1997

Spectrochemical investigations of fluorescence quenching agents. Part 5. Effect of surfactants of the ability of nitromethane to selectively quench fluorescence emission of alternant PAHs.

Applicability of the nitromethane selective quenching rule for discriminating between alternant vs. nonalternant polycyclic aromatic hydrocarbons (PAHs) is examined for 18 representative PAH solutes dissolved in micellar cetyltrimethylammonium chloride (CTACl), micellar dodecyltrimethylammonium bromide (DTAB), micellar Brij-35 and micellar sodium octanoate (SO) solvent media. Experimental results show that nitromethane quenched fluorescence emission of only the 10 alternant PAHs in the two cationic (CTACl and DTAB) and nonionic Brij-35 surfactant solvent media as expected. Emission intensities of nonalternant PAHs, except for the few exceptions noted previously, were unaffected by nitromethane addition. Unexpected quenching behavior was observed, however, in the case of nonalternant PAHs dissolved in micellar sodium octanoate solvent media. Nitromethane quenched fluorescence emission of all nonalternant PAHs studied in the SO solvent media, which is contrary to the selective quenching rule.

Fluorescent Dyes↗
PubMed2002

Investigation of capillary electrophoresis-laser induced fluorescence as a tool in the characterization of sewage effluent for fluorescent acids: determination of salicylic acid.

The investigation of emerging contaminant issues is a proactive effort in environmental analysis. As a part of this effort, sewage effluent is of current analytical interest because of the presence of pharmaceuticals and their metabolites and personal care products. The environmental impact of these components is still under investigation but their constant perfusion into receiving waters and their potential effect on biota is of concern. This paper examines a tool for the characterization of sewage effluent using capillary electrophoresis-laser induced fluorescence (CE-LIF) with a frequency-doubled laser operated in the ultraviolet (UV). Fluorescent acidic analytes are targeted because they present special problems for techniques such as gas chromatography-mass spectrometry (GC-MS) but are readily accessible to CE-LIF. As an example of the application of this tool, salicylic acid is determined near the 100 ng/L (7 x 10(-10) M) level in sewage effluent. Salicylic acid is a metabolite of various analgesics. Relatively stable in the environment, it is a common contaminant of municipal sewage systems. Salicylic acid was recovered from freshly collected samples of the effluent by liquid-liquid extraction. Confirmation of identity was by electron ionization GC-MS after conversion of the salicylic acid to the methyl ester by means of trimethylsilyldiazomethane. CE-LIF in the UV has revealed more than 50 individual peaks in the extract and a background response that suggests a large and indeterminate number of additional compounds are present. These data together with complementary techniques provide information on the complexity and components in these effluent streams.

Carboxylic Acids↗
PubMed1995

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XXVIII: Oligoamines with fluorescent properties. Part C: Fluorescent oligoamines with enhanced hydrophilic properties.

Fifteen fluorescent oligoamines with one or two fluorescent groups and two or three basic N-functions were prepared and tested for antiplatelet activity (Born-test). Five compounds involving three different fluorophores, i.e. 2-fluorenyl, 1-pyrenyl, and 9-phenanthryl, show an IC50 of 7-11 mumol/L. They are suitable to serve as probes in the field of oligoamine-biopolymere interactions.

Amines↗
PubMedDate not supplied

Intrinsic fluorescence of enzymes and fluorescence of chemically modified enzymes for analytical purposes: a review.

In recent years our research group has developed new alternatives for fluorescence enzymatic determinations. First, we observed that the intrinsic fluorescence of enzymes changes during enzymatic reactions, proportionally to the substrate concentration, avoiding the combination of the enzymatic reaction with a fluorophore-involving reaction. The main disadvantage of this method is that the excitation and emission wavelengths of the enzymes are in the UV region of the spectrum. An alternative to overcome this problem consisted of covalently bonding the enzyme to a fluorophore. In this paper, an overview is given of all of the applications and future developments on both types of alternatives that we have developed. Apart from the analytical characteristics of the methods, we have also reviewed all of the information about mathematical models we have elaborated to date.

Enzymes↗
PubMed1995

Fluorescence energy transfer in one dimension: frequency-domain fluorescence study of DNA-fluorophore complexes.

Fluorescence resonance energy transfer among linear DNA bound fluorophores was carried out to study the process in one dimension. The donor fluorescence intensity decays in the case of energy transfer in one dimension are stretched exponential and show exp[-(t/tau)1/6] time dependence, which results in an initial more rapid decay and subsequent slower decay at long times when compared to those in higher dimensions. DNA-bound 4',6'-diamidino-2-phenyl indole (DAPI), acridine orange (AO), and ethidium bromide (EB) were used as donors. The acceptors were in the case of DAPI AO and EB; in the case of AO nile blue (NB), methylene blue (MB), and crystal violet (CV); and NB, MB, and oxazine 750 in the case of EB. As expected, the donor intensity decays became highly heterogeneous upon energy transfer and were characterized by the simultaneous presence of both highly and marginally quenched donors. The intensity decays for all three donors in the presence of various acceptors are satisfactorily described by the Förster model of energy transfer in one dimension. The intensity decays also allow for clear rejection of a two- or three-dimensional model. The experimentally recovered critical Förster distances (R0) ranged between 37 A in the case of DAPI and EB to 70 A in the case of AO and CV donor-acceptor pairs. These recovered R0 values compare reasonably with those calculated from spectral properties if we use values of 1.25 for k2, and 1.5 for the refractive index of DNA. The k2 value will be even higher, between 1.5 and 2.0, if the consensus DNA refractive index of 1.75 is used. These k2 values strongly suggest that the dipoles of the acceptor chromophores when bound to DNA are not randomly oriented but are aligned preferentially in plane.

Acridine Orange↗
PubMed1991

Bivariate flow karyotyping of human chromosomes: evaluation of variation in Hoechst 33258 fluorescence, chromomycin A3 fluorescence, and relative chromosomal DNA content.

The total variation of chromosome peak positions, in bivariate distributions of Hoechst 33258 and chromomycin A3 fluorescence of 19 healthy individuals, was compared with the experimental variation, determined from 23 bivariate distributions of chromosomes prepared separately from a single cell lineage. The experimental variation in Hoechst and chromomycin fluorescence and the relative chromosomal DNA content were determined from experiments performed over several days. The additional variance contributed by time was the same as the daily variance. The accuracy by which the relative chromosomal DNA content can be calculated from bivariate peak positions was investigated. A least squares method was used to fit the distributions of relative DNA content, obtained, respectively, from mono- and bivariate flow analyses of chromosomes from the same cell lineage. In general the DNA contents match quite well, but for a few chromosomes a difference was found, statistically discernible at the 5% level. The average relative chromosomal DNA content of the chromosomes from the 19 normal individuals, calculated from bivariate peak positions, showed a linear relation with the estimates published by other investigators.

Bisbenzimidazole↗
PubMed1997

Capillary electrophoresis of herbicides: IV. Evaluation of octylmaltopyranoside chiral surfactant in the enantiomeric separation of fluorescently labeled phenoxy acid herbicides and their laser-induced fluorescence detection.

A novel chiral nonionic surfactant, namely octyl-b-D-maltopyranoside (OM), was evaluated in chiral capillary electrophoresis of fluorescently labeled phenoxy acid herbicides. The labeling of the analytes with 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) permitted a concentration detection limit of 5 x 10-10 M using laser-induced fluorescence detection. This limit of detection allowed the determination of ultradiluted solutions of the ANDSA-derivatized phenoxy acid herbicides whose concentration was a low as 10-11 M (i.e. 2.2 ppt) by applying the concept of field-amplified sample stacking (FASS). The sample injection by FASS did not adversely affect separation efficiencies, resolution and reproducibility of the electrophoretic system. The tagging of the phenoxy acid herbicides with ANDSA increased the hydrophobicity of the analytes, thus favoring an enhanced solubilization of the derivatized herbicides in the OM micellar phase. The net results of this effect were a much shorter analysis time and an improved enantiomeric resolution of the derivatives when compared to underivatized phenoxy acid herbicides. The optimum surfactant concentration required for maximum resolution decreased with increasing hydrophobicity of the analyte, with the least hydrophobic analyte requiring higher surfactant concentration. Because of the two permanently charged sulfonic acid groups of the ANDSA tag, the pH of the running electrolyte had little effect on the enantiomeric resolution of the derivatized herbicides. Due to its salting-out effect and increasing the micellized surfactant concentration, increasing the ionic strength of the running electrolyte increased the enantiomeric resolution of the least hydrophobic analytes. Conversely, increasing the percent methanol in the running electrolyte decreased the enantiomeric resolution of the least hydrophobic analytes due to a decrease strength of solute-micelle association. For hydrophobic analytes, existed an optimum percent of methanol existed for maximum enantiomeric resolution.

2-Naphthylamine↗
PubMed1994

Adsorption of a novel fluorescent derivative of a poly(ethylene oxide)/poly(butylene oxide) block copolymer on octadecyl glass studied by total internal reflection fluorescence and interferometry.

We have used total internal reflection fluorescence (TIRF) to measure the adsorption kinetics of a newly synthesized fluorescent derivative of a triblock copolymer comprising two poly(ethylene oxide) arms connected by a poly(butylene oxide) segment. The composition is (EO)400 (BO)55 (EO)400, in which EO represents ethylene oxide, BO represents butylene oxide, and one or both of the terminal OH groups of the two (EO)400 arms are labeled with tetramethylrhodamine. The poly(butylene oxide) segment binds to hydrophobic octadecyl glass, used as a substratum. The TIRF signal is shown to be derived almost entirely from surface-adsorbed polymer. This facilitates calculation of adsorption isotherms from 0.1-0.005% bulk polymer solution by means of diffusion kinetics. Information about the effective thickness of the adsorbed polymer, determined by optical interference microscopy, corresponds with what is known about the conformation of similar molecules at interfaces and indicates monolayer adsorption on the glass.

Adsorption↗
PubMed1986

Fluorescent opsonization assay: binding of plasma fibronectin to fibrin-derivatized fluorescent particles does not enhance their uptake by macrophages.

A simple method for assessing the opsonic properties of plasma fibronectin is described. The method is based on the uptake of protein-derivatized fluorescent particles by mouse peritoneal macrophages. With this system, fibronectin stimulated the uptake of gelatin conjugated to carboxylated fluorescent particles. In contrast to the gelatinized particles, neither the covalent nor noncovalent interaction of fibronectin with fibrin particles stimulated their uptake by macrophages. These results provide additional evidence that fibronectin is not a conventional opsonin and that enhanced phagocytosis is not an obligatory response by macrophages to fibronectin-coated particles.

Animals↗
PubMed1975

Fluorescence reactions of fluorescamine with levodopa and its derivatives: fluorescence assay of 3-methoxy-4-hydroxyphenylalanine in levodopa dosage forms.

A simple fluorometric method for the quantitation of 3-methoxy-4-hydroxyphenylalanine, either alone or in the presence of levodopa, is presented. Fluorescence is developed by reaction with fluorescamine. The interactions of this reagent with levodopa and a number of its derivatives under various experimental conditions were studied. Negligible fluorescence was obtained with levodopa, dopamine, levodopa benzyl ester, and 6-hydroxydopamine.

Chemical Phenomena↗
PubMed2003

Comparison between fluorescence in situ hybridization (FISH) and quantitative-fluorescent polymerase chain reaction (QF-PCR) for the detection of aneuploidies in single blastomeres.

OBJECTIVES: The aim of our investigation was to compare the efficiencies of the fluorescence in situ hybridization (FISH) and the quantitative-fluorescent PCR (QF-PCR) methods for the detection of sexing and numerical chromosome disorders in single blastomeres collected from the same preimplantation human embryos. METHODS: FISH analysis was carried out on 145 blastomeres from the 79 surplus embryos with probes specific for chromosomes 13, 18, 21, X, and Y. QF-PCR was performed with each one or two of the primers specific for the same chromosomes on 151 blastomeres from the same embryos obtained from patients undergoing IVF treatment. RESULTS: Analyses were possible on 135 blastomeres (93%) by FISH and on 117 blastomeres (77%) by QF-PCR. Of 65 embryos, which could be analyzed by both methods, 20 embryos (31%) were diagnosed as abnormal. CONCLUSION: The present study shows that FISH tests are more accurate than QF-PCR assays for the detection of numerical chromosome disorders when performed on single blastomeres.

Aneuploidy↗
PubMed1996

Characterization of fluorescent nucleoside triphosphates by capillary electrophoresis with laser-induced fluorescence detection: action of alkaline phosphatase and DNA polymerase.

A method of analysis of fluor-labeled nucleoside triphosphates based on alkaline phosphatase-catalyzed sequential cleavage of phosphate groups with monitoring of all fluorescent species by capillary electrophoresis with laser-induced fluorescence detection is presented. The method allows determination of the purity of the triphosphate samples as well as the relative amounts of the lower phosphate contaminants. The ability of one of the fluor-labeled nucleoside triphosphates to serve as polymerase substrate was verified by labeling DNA restriction fragments by the method of filling recessed 3'-ends using DNA polymerase Klenow fragment.

Adenosine Triphosphate↗
PubMed1997

An isocratic assay for norepinephrine, dopamine, and 5-hydroxytryptamine using their native fluorescence by high-performance liquid chromatography with fluorescence detection in discrete brain areas of rat.

A rapid and simple isocratic chromatographic procedure for simultaneous determination of norepinephrine (NE), dopamine (DA), and 5-hydroxytryptamine (5-HT) using their native fluorescence by high-performance liquid chromatography coupled to fluorescence detection (HPLC-FD) is described. Since the present procedure does not involve sample prepurification, the recovery of monoamines was more than 97% (n = 12) and within a given run, coefficient of variation was less than 3.1% (n = 12). Accordingly, use of an internal standard is not mandatory. In a single chromatographic run, levels of NE, DA, and 5-HT can be determined in less than 30 min. The minimum concentration of monoamines which could be detected by this method was found to be 250 pg for NE and DA and 100 pg for 5-HT. The validity of the method was confirmed by the estimation of levels of monoamines in the hypothalamus and striatum of rat brain following treatment with clorgyline, a monoamine oxidase inhibitor.

Amines↗
PubMed1999

Quantitation of fluorescent nucleotide incorporation by capillary gel electrophoresis and laser-induced fluorescence detection.

A method has been developed by which enzymatically incorporated fluorophore-labeled nucleotide sites in nucleic acid can be quantitated by degradation of nanogram quantities of DNA followed by capillary gel electrophoretic analysis with fluorescence detection. In this way the differing relative labeling densities achieved using either C5-substituted dUTP's or N4-substituted dCTP's were determined. The method has proven to be very useful in obtaining quantitative analytical data from the small quantities of complex molecules produced in nick translations. Various polymerization conditions using DNA polymerase I were examined to determine optimal labeling density. Simultaneous copolymerization of green fluorescing dCTP and dUTP nucleotides were undertaken in an attempt to maximize labeling density.

DNA↗
PubMed2000

Feasibility of simultaneous fluorescence immunophenotyping and fluorescence in situ hybridization study for the detection of estrogen receptor expression and deletions of the estrogen receptor gene in breast carcinoma cell lines.

For the first time, combined immunophenotyping and fluorescence in situ hybridization (FISH) technique according to the "fluorescence immunophenotyping and interphase cytogenetics as a tool for investigation of neoplasms" (FICTION) technique have been successfully applied in solid tumors. Thus, we were able to visualize the antigen expression of cells with chromosomal deletions of a tumor suppressor region directly. In six breast carcinoma cell lines, we investigated the correlation between estrogen receptor (ER) expression status and deletions of the estrogen receptor gene (ESR). To screen for deletions of the ESR gene, dual-color FISH was performed with a YAC (yeast artificial chromosome) probe containing the ESR gene and, as internal control, with a centromeric probe of chromosome 6. Deletions of the ESR gene were detected in four of six cell lines. For direct comparison of ER expression with the copy number of the ESR gene at the single cell level, immunophenotyping with mouse anti-human ER antibody was combined with FISH with the YAC probe containing the ESR gene according to the FICTION technique. There was no correlation between lack of or reduced ER expression and deletions of the ESR gene. One cell line with deletions of the ESR gene did express ER on the protein level, while another cell line without a deletion did not. Cells with deletions of the ESR gene were either ER expression positive or negative. The staining intensity of ER expression was not associated with the copy number of the ESR gene. Thus, this FICTION study unequivocally shows that deletions of the ESR gene are not the major cause of absent or reduced ER expression in breast carcinoma cell lines.

Animals↗
PubMed1989

Enhancement of chlorophyll a fluorescence yield, low-temperature F685/F730 fluorescence emission ratio, and electron transport rate by ether phospholipids (platelet activating factor and analogs) in isolated chloroplasts.

Acetyl glyceryl ether phosphorylcholine (1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine; or platelet activating factor (PAF)), when incubated with chloroplasts or subchloroplast fractions derived from stroma or grana lamellae, induces a drastic increase in the low-temperature fluorescence emission ratio F685/F730 (77 degree K). The molecular structure requirement for the effect to be elicited is the ether bond and a long C chain at the C-1 position of glycerol, a short C chain at C-2 (or the lyso form), and a large polar head at C-3, the potent effector being PAF C-16. The effect is more pronounced in grana-derived fractions. PAF also induces an increase in the chlorophyll alpha fluorescence yield, enhances the association of chlorophyll in the supramolecular pigment-protein complexes of the thylakoid (especially those of Photosystem II), and enhances electron transfer from 1,5-diphenyl carbazide to 2,6-dichlorophenol. These effects are attributed to alteration of the Photosystem II unit organization via the incorporation/intercalation in the grana of the wedge-shaped PAF.

Chlorophyll↗
PubMed1978

Changes in fluorescence of 8-anilino-1-naphthalene sulfonate after bacteriophage T5 infection of Escherichia coli. Initial fluorescence rise coincides with onset of rubidium efflux.

Escherichia coli cells pre-loaded with 86Rb+ begin to lose 86Rb+ immediately after phage T5 addition. The loss proceeds with negative-exponential (first-order) kinetics for up to approximately 15 min after phage addition. The constant which characterizes the rate of loss increases with increasing numbers of infecting phage per cell. It is known that anaerobic, fermenting cells of E. coli show a two-step increase in 8-anilino-1-naphthalene sulfonate (ANS) fluorescence upon infection with bacteriophage T5; the first rise begins immediately upon phage addition, the second 6 min later. The onset of 86Rb+ release, therefore, is correlated with the first fluorescence rise with respect to timing and response to the multiplicity of infection.

Aerobiosis↗
PubMed1985

Tryptophan fluorescence of sarcoplasmic reticulum ATPase. A fluorescence quench study.

The calcium-dependent change in the tryptophan fluorescence intensity of the sarcoplasmic reticulum Ca2+- and Mg2+-ATPase was investigated using different quenching reagents. It is demonstrated that only those compounds which are bound to the enzyme (i.e., 1-(9,10-dibromomyristoyl)-sn-2-glycerophosphorylcholine and 1-(9,10-dibromostearoyl)-sn-glycero-3-phosphorylcholine) are able to decrease the amplitude of the fluorescence decrement observed after removal of calcium ions. From the position of the bromine atom within the lysophosphatidylcholines, it is concluded that the tryptophan residues involved are located in the hydrophobic part of the ATPase molecule and are in contact with the hydrocarbon chains of the phospholipids.

Adenosine Triphosphatases↗