Intense Fluorescence Band Research Articles

Express method for detection of Amanita phalloides amanitine toxins

Spectral studies of the interaction between amanitine and ethidium bromide fluorophore showed the appearance of a new intensive fluorescence band after addition of amanitine to ethidium bromide solution, caused by the formation of a charge-transfer complex. The new fluorescence band is located in a shorter wave region of the spectrum compared to ethidium bromide fluorescence band. Based on the results, a rapid fluorescent method for detection of amanitines was developed.

2-Aryl-3-hydroxyquinolones, a new class of dyes with solvent dependent dual emission due to excited state intramolecular proton transfer

Herein, the fluorescence properties of a series of 2-aryl-3-hydroxyquinolones (3HQs) were investigated and compared with the properties of well-studied 3-hydroxyflavone. All these compounds were found to display dual fluorescence with well-separated bands in organic solvents and aqueous solutions. Using steady-state and time-resolved fluorescence spectroscopy, we showed that their dual fluorescence is due to an excited state intramolecular proton transfer reaction. Moreover, the absorption spectra of most 3HQs tested were found to be similar, indicating that they are not sensitive to the substituent at the 2-aryl ring. This was related by quantum chemical calculations to the non-planarity of these molecules which prevents conjugation between the two aromatic moieties. The only exception was the 3HQ derivative with a thiophene ring at position 2 which exhibited a red-shifted spectrum due to its more planar structure. In sharp contrast, the emission spectra and especially the intensity ratio of the two emission bands were highly dependent on the substituents at the 2-aryl ring and at the heterocyclic nitrogen. Moreover, N-methyl substituted 3HQs (N–Me 3HQs) demonstrate strong solvatochromic properties, with large changes in their fluorescence band intensity ratio as a function of the solvent polarity. In addition, the logarithm of these intensity ratios varied linearly with the Hammett constant associated with the substituent in the 2-aryl ring, enabling the design of 3HQ dyes with optimized intensity ratios in a given range of solvent polarities. Thus, 3HQs preserve the unique properties of 3-hydroxyflavones, namely dual emission that is highly sensitive to solvent polarity and to chemical substituents. Moreover, in comparison to 3-hydroxyflavones, 3HQ dyes exhibit higher fluorescence quantum yields and 10-fold increased photostability. These properties of the 3HQ derivatives make them prospective candidates for application as polarity-sensitive fluorescent labels for biomolecules.

The analysis of oligosaccharides derived from different sources by fluorophore-assisted carbohydrate electrophoresis

Fluorophore-assisted carbohydrate electrophoresis (FACE) is a straightforward, sensitive method for determining the presence and relative abundance of individual (oligo)saccharide in a(n) (oligo)saccharide mixture. The single terminal aldehydes of oligoglucoside residues released by acid hydrolysis of β-1, 3- d-glucan from yeast were tagged with the charged fluorophore 8-aminonaphthalene-1,3,6-trisulfonate (ANTS), and separated with high resolution on the basis of size by polyacrylamide gel electrophoresis. ANTS fluorescence labeling was not biased by oligoglucoside length; therefore, band fluorescence intensity was directly related to the relative abundance of individual oligoglucoside moieties in heterogeneous sample. Therefore, FACE represents an accessible, sensitive, and quantitative analytical tool enabling the analysis of (oligo)saccharides derived from different sources.

Hydrolysis characteristics of a β‐1,3‐d‐glucan elicitor from yeast

Fluorophore-assisted carbohydrate electrophoresis (FACE) is a straightforward, sensitive method for determining the presence and relative abundance of individual (oligo)saccharides in a(n) (oligo)saccharide mixture. The single-terminal aldehydes of oligoglucoside residues released by acid hydrolysis of beta-1,3-D-glucan from yeast were tagged with the charged fluorophore ANTS (8-aminonaphthalene-1,3,6-trisulphonate), and separated with high resolution on the basis of size by PAGE. ANTS fluorescence labelling was not biased by oligoglucoside length; therefore band fluorescence intensity was directly related to the relative abundance of individual oligoglucoside moieties in a heterogeneous sample. FACE analysis revealed that the major oligoglucoside mixture released by acid hydrolysis from beta-1,3-D-glucan was composed of monosaccharide, disaccharide, trisaccharide, tetrasaccharide, pentasaccharide, hexasaccharide, heptasaccharide and octasaccharide, and the order of abundance from high to low was trisaccharide, monosaccharide, disaccharide, tetrasaccharide, pentasaccharide, hexasaccharide, heptasaccharide and octasaccharide respectively. In conclusion, FACE represents an accessible, sensitive and quantitative analytical tool enabling the characterization of a(n) (oligo)saccharide mixture.

Preparation and Photophysics of 2-(1-Pyrenyl)acrylic Acid and Its Methyl and 2′,2′,6′,6′-Tetramethyl-4′-Piperidyl Esters

Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO.). Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. The spectrum in neutral methanol indicates that it originates from the anionic form -COO(-). Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form -COOH and the cationic form -COOH(2) (+). The ester analogues did not show any changes in various pH conditions. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1'-oxo-2',2',6',6'-tetramethyl-4'-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO.).

Studies on the Hydrolytic Condition of β‐1,3 Glucan from Yeast by Fluorophore‐Assisted Carbohydrate Electrophoresis

Fluorophore‐assisted carbohydrate electrophoresis (FACE) is a straightforward, sensitive method for determining the presence and relative abundance of individual (oligo)saccharide in a(n) (oligo)saccharide mixture. The single‐terminal aldehydes of oligoglucoside residues released by acid hydrolysis of β‐1,3 glucan from yeast were tagged with the charged fluorophore 8‐aminonaphthalene‐1,3,6‐trisulfonate (ANTS) and separated with high resolution on the basis of size by polyacrylamide gel electrophoresis. ANTS fluorescence labeling was not biased by oligoglucoside length; therefore, band fluorescence intensity was directly related to the relative abundance of individual oligoglucoside moieties in heterogeneous samples. FACE analysis revealed that the major oligoglucoside mixture released by acid hydrolysis from β‐1,3 glucan was composed of monosaccharide, disaccharide, trisaccharide, and tetrasaccharide, respectively. And the best hydrolytic condition is at a concentration of 2.0 mol/L TFA, heated at 85°C for 2.0 h. In conclusion, FACE represents an accessible, sensitive, and quantitative analytical tool enabling the characterization of a(n) (oligo)saccharide mixture. The results of these bioassays demonstrated that the sample obtained on the condition of 2.0 h, 85°C, 2.0 mol/L was the most active as compared to the sample obtained on the other conditions in eliciting phytoalexin accumulation in tobacco cotyledon tissue. The project was financially supported by “The Scaling the Height Program” of the State Science and Technology Committee of China.

Crystal Structures and Spectroscopic Properties of Zinc(II) Ternary Complexes of Vitamin L, H′ and Their Isomer <i>m</i>-Aminobenzoic Acid with Bipyridine

The crystal structures of the three Zn(II) complexes, [Zn(bpy)(o-AB)2] (1) (bpy=2,2'-bipyridine, o-AB=o-aminobenzoic acid=Vitamin L), [Zn(bpy)(m-AB)Cl]2 (2) (m-AB=m-aminobenzoic acid), [Zn(bpy)(p-AB)Cl]*p-AB*H2O (3) (p-AB=p-aminobenzoic acid=Vitamin H'), have been determined and the basic coordination geometries and architectures organized by hydrogen-bonds and pi-pi interactions also characterized. The substitute amine group at ortho-, meta-, and para-position of AB plays an important role to produce completely different coordination motif of these complexes, further, in all complexes, aromatic amines are not coordinated to Zn(II) atom. While two different types of coordination modes of the carboxylate O atoms are present in these complexes: one mode consists of the usual Zn-O bond lengths (2.009(2)-2.251(2) A) in complex 1, 2 and 3; another consists of a very long Zn-O bond lengths (2.422(2) A) in complex 1. Each of the complexes has the characteristic UV absorption bands around 250-310 nm region, and the intense fluorescence band at near 325 nm.

Synthesis and structural characterization of zinc(II) and cadmium(II) complexes with 2-oxo-1,3-dithiole-4,5-dithiolate and 1,10-phenanthroline

Isomorphous complexes Zn(dmid)(phen) 2 ( 1) and Cd(dmid)(phen) 2 ( 2) have been synthesized through a ligand substitute reaction. Their structures and properties have been characterized by elemental analysis, IR, UV–Vis, fluorescence and single-crystal X-ray analysis. The octahedral N 4S 2 coordination geometry, bonding, electronic structure and IR spectra of the Zn(dmid)(phen) 2 molecule were studied in detail using DFT and INDO/S methods. In the crystal packing, there exists a strong π–π interaction between two parallel 1,10-phenanthrolines of adjacent molecules. Complex 1 (or 2) in the solid state exhibits an intensive fluorescence band at 539.5 nm (or 536 nm) when the excitation wavelength is 371 nm (or 370.5 nm) at room temperature.

Ground and excited-state electronic interactions in poly(propylene amine) dendrimers functionalized with naphthyl units: effect of protonation and metal complexation.

We report the absorption spectra and the photophysical properties (fluorescence spectrum, quantum yield, and lifetime) of four dendrimers of the poly(propylene amine) family (POPAMs) functionalized at the periphery with naphthylsulfonamide (hereafter called naphthyl) units. Each dendrimer Gn, where n = 1 to 4 is the generation number, comprises 2n + 1 (i.e., 32 for G4) naphthyl functions in the periphery and 2n + 1--2 (i.e., 30 for G4) tertiary amine units in the branches. All the experiments have been carried out in acetonitrile solutions. Comparison with two reference compounds (N-methyl-naphthalene-2-sulfonamide, A, and N-(3-dimethylamino-propyl)-2-naphthalene-1-sulfonamide, B) has shown that the absorption spectra of the dendrimers are significantly different from those expected from the component units. Furthermore, the intense fluorescence band of the naphthyl unit (lambda max = 343 nm; phi = 0.15, tau = 8.5 ns) is strongly quenched in the dendrimers. The quenching effect increases with increasing generation and is accompanied by the appearance of a weak and broad emission tail at lower energy. Protonation of the amine units of the dendrimers by addition of CF3SO3H (triflic) acid causes a strong increase in the intensity of the naphthyl luminescence and a change in the form of the emission tail. The shapes of the titration curves depend on dendrimer generation, but in any case, the effect of the acid can be fully reversed by successive addition of a base (tributylamine). The results obtained show that in the dendrimers there are interactions (both in the ground and excited states) between naphthyl units as well as between naphthyl units and amine units of the branches; this gives rise to dimer/excimer and charge-transfer/exciplex excited states. Titration with Zn(CF3SO3)2 has the same effect as acid titration, as far as the final emission spectrum is concerned, but a much higher concentration of Zn(CF3SO3)2 has to be used and the shapes of the titration plots are very different. Titration with Co(NO3)2.6H2O causes a much smaller increase in the intensity of the naphthyl fluorescence compared with Zn(CF3SO3)2. The results obtained have shown that protonation and metal coordination can reveal the presence of ground and excited state electronic interactions in functionalized poly(propylene amine) dendrimers, and that the presence of photo-active units in the dendrimers can be useful to reveal some peculiar aspects of the protonation and metal coordination processes.

Dynamic Fluoride Anion Coordinating Si-Containing π-Conjugating Polymers

Three types of poly[dialkylsilylenephenyleneethynylenephenylene]s (dialkyl: 2 for n-dodecylmethyl; 5a for di-n-hexyl; 5b for di-n-hexyl-co-dimethyl) were newly prepared by the AB- and AA−BB-type coupling reactions. These polymers afforded moderate molecular weights (Mw) in the range 7.6 × 103−27 × 103. As the amount of tetra-n-butylammonium fluoride (TBAF) increases in a THF solution of 2, two π−π* absorption bands at 298 and 317 nm due to the phenyleneethynylenephenylene moiety significantly decreased. Simultaneously, a new intense absorption band at 390 nm characteristic of intramolecular charge transfer (ICT) appeared in place of the original ICT absorption band at 342 nm. Also, the intensity of fluorescence band around 393 nm (excited at 342 nm) significantly decreased upon the addition of TBAF. The changes in UV−vis absorption and fluorescence spectra of the polymers were readily seen by naked eye. As for 2, a novel three-step titration curve of UV absorbance (or apparent GPC retention time) as a fu...

Luminescent lanthanide ions hosted in a fluorescent polylysin dendrimer. Antenna-like sensitization of visible and near-infrared emission.

We have investigated the complexation of the luminescent Nd(3+), Eu(3+), Gd(3+), Tb(3+), Er(3+), and Yb(3+) ions by a polylysin dendrimer containing 21 amide groups in the interior and, in the periphery, 24 chromophoric dansyl units which show an intense fluorescence band in the visible region. Most of the experiments were performed in 5:1 acetonitrile/dichloromethane solution at 298 K. On addition of the lanthanide ions to dendrimer solutions, the fluorescence of the dansyl units is quenched; in Nd(3+), Er(3+), and Yb(3+), a sensitized near-infrared emission of the lanthanide ion is observed. At low metal ion concentrations, each dendrimer hosts only one metal ion and when the hosted metal ion is Nd(3+) or Eu(3+), the fluorescence of all the 24 dansyl units of the dendrimer is quenched with unitary efficiency. Quantitative measurements were performed in a variety of experimental conditions, including protonation of the dansyl units and measurements in rigid matrix at 77 K where a sensitized Eu(3+) emission could also be observed. The results obtained have been interpreted on the basis of the energy levels and redox potentials of dendrimer and metal ions.

Spectroscopic Measurements of Temperature with Uranyl Compounds

A new class of fluorescent probes for measuring temperature is described. The intensities of the strong fluorescence bands of uranyl acetate, uranyl nitrate hexahydrate, and uranyl orthophosphate were recorded when the uranyl compound was illuminated with an argon-ion laser operating at 488 nm. The intensity ratio of two fluorescence bands of uranyl acetate at room temperature were determined for five freshly prepared samples and shown to be independent of the intensity of the laser excitation and optical alignment. The intensities of the fluorescence bands lying between 500 and 570 nm were measured at various temperatures ranging from 77 to 295 K. The ratio of the intensities of two fluorescence bands was calculated and shown to vary linearly with temperature. A linear fit provided the slope. The largest positive slope of all the intensity ratios associated with uranyl acetate was 6.02 × 10−3 K−1, that associated with uranyl orthophosphate was 4.68 × 10−3 K−1, and that associated with uranyl nitrate hexahydrate was 1.81 × 10−3 K−1. The potential of uranyl compounds as a new group of temperature probes is discussed.

Novel fluorescence probes based on 2,6-donor-acceptor-substituted anthracene derivatives.

[reaction: see text] The fluorescence properties of selected derivatives of 6-methoxyanthracene-2-carboxylic acid were studied. The corresponding ester and oxazoline derivatives exhibit a moderate solvatochromism, which is caused by the donor-acceptor interplay. The fluorescence band shift and intensity of oxazoline 1f may be reversibly modulated by protonation or complexation with silver ions; thus, the oxazoline heterocycle serves as a useful substituent with switchable acceptor strength.

Relative abundance of oligosaccharides in Candida species as determined by fluorophore-assisted carbohydrate electrophoresis.

Fluorophore-assisted carbohydrate electrophoresis (FACE) is a straightforward, sensitive method for determining the presence and relative abundance of individual oligomannosyl residues in Candida mannoprotein, the major antigenic determinant located on the outer surface of the yeast cell wall. The single terminal aldehydes of oligomannosyl residues released by hydrolysis were tagged with the charged fluorophore 8-aminonaphthalene-1,3,6-trisulfonate (ANTS) and separated with high resolution on the basis of size by polyacrylamide gel electrophoresis. ANTS fluorescence labeling was not biased by oligomannoside length; therefore, band fluorescence intensity was directly related to the relative abundance of individual oligomannoside moieties in heterogeneous samples. FACE analysis revealed the major oligomannosides released by acid hydrolysis and beta-elimination of Fehling-precipitated mannan from Candida albicans, which were the same as those previously reported in studies based on mass and nuclear magnetic spectroscopic analysis. FACE was also amenable to the analysis of samples obtained by direct hydrolysis of whole yeast cells. Whole-cell acid hydrolysis and whole-cell beta-elimination of two isolates each of C. albicans, C. glabrata, C. krusei, C. lusitaniae, C. parapsilosis, C. rugosa, C. stellatoidea, and C. tropicalis resulted in oligomannoside gel banding patterns that were species and strain specific for the 16 isolates surveyed. Whereas some bands were specific for an individual isolate or species, other bands were shared by two or three species in various groupings. Differences in the mannoprotein composition of C. albicans A9 and four spontaneous cell surface mutants were also detected. Mannan "fingerprints," or banding pattern profiles, derived from the electrophoretic mobilities of individual bands relative to the migration of acid-hydrolyzed dextran (relative migration index) yielded profiles characteristic of individual isolates not revealed by standard assimilation and biochemical profiles. FACE represents an accessible, sensitive, and quantitative analytical tool enabling the characterization of yeast mannan complexity.

Effect of detergents on the fluorescence from CdS-Q clusters prepared using variable excess Cd 2+ concentrations

The effect of surfactants Triton X-100 (TX-100, neutral), cetyltrimethylammonium chloride (CTAC, cationic) and sodium dodecyl sulfate (SDS, anionic) on the intensity and lifetime of several fluorescence bands of Q-CdS clusters, which were prepared with variable excess Cd 2+ concentration, was studied. The fluorescence intensity of the several clusters of Q-CdS is strongly increased by adding a little excess of Cd 2+. When more Cd 2+ is added, a moderate increment of fluorescence intensity is observed and then, at higher excess Cd 2+ concentrations, the fluorescence intensity remains nearly constant. The effect of the detergents on the fluorescence was found to depend on the excess of Cd 2+ added to the cluster. The quenching of the fluorescence from Q-CdS by CTAC and SDS render linear Stern–Volmer plots. The corresponding values of the Stern–Volmer constants ( K sv) are lowered when the excess cadmium concentration is increased. For TX-100 the Stern–Volmer plots were non-linear for all the clusters with all the excess cadmium concentrations used. Two different zones, corresponding to different responses of the system in two concentration ranges are observed: the first one at TX-100 concentrations lower (zone I) and the second one at TX-100 concentrations higher (zone II), than 2×10 −4 M, which is equal to the concentration of the polyphosphate used to stabilize the colloid. According to the experimental results, we believe that TX-100 quenching, for all the CdS clusters’ fluorescence bands in the range of final cadmium concentration used for the experiments, is a polyphosphate-assisted process in zone I, while in zone II this assistence is not evident. The fluorescence decay curves were also determined in all the cases. They were not altered, for any of the clusters, by the addition of TX-100 and SDS, pointing to static quenching processes in both cases. On the other side, the fluorescence lifetimes were shortened by the addition of CTAC, which is indicative that, at least in part, the quenching process is dynamic for this cationic detergent.

Synthesis, Fluorescence Properties, and Head-to-Tail Regioselectivity in the Photodimerization of a Donor–Acceptor-Substituted Anthracene

The novel 2,6-donor–acceptor-substituted anthracene, namely 6-methoxy-2-anthracene carboxylic acid (7), was synthesized. The emission of this compound exhibits significant solvatochromism. The fluorescence band position and intensity are also remarkably sensitive to H+. Irradiation of the anthracene 7 in solution yields the syn and anti head-to-tail dimers exclusively. A synergistic electronic effect between the donor and acceptor substituents is proposed to operate on the photophysical and photochemical properties of anthracene 7.

Mechanistic Studies of Photochemical Silylene Extrusion from 2,2-Diphenylhexamethyltrisilane

Photophysics and photochemistry of 2,2-diphenylhexamethyltrisilane (1) was investigated in detail. Diphenyltrisilane 1 showed an intense fluorescence band assignable to the intramolecular charge-tr...

Synthesis and characterization of a one‐dimensional polymeric copper (II)‐tetrathioporphyrazine

AbstractThe title polymer PCuS4P5 was synthesied by reaction of 2,3‐dicyano‐5,6‐dihydro‐1,4‐dithiin, pyromellitic dianhydride and urea with cuprous salt in optimized gentle method. The structure and properties of the PCuS4P5 were characterized by elemental analysis, X‐ray powder diffraction, IR, UV‐Vis, fluorescence and EPR spectra and variable‐temperature magnetic susceptibility. The polymer is black sublimable crystallite and the degree of polymerisation has been found to be n>4. The PCuS4P5 in H2SO4 exhibits intensive absorption bands at 236, 342, 656 and 767 nm and intensive fluorescence band at 410 nm or 464 nm under the excitation of the ultraviolet light of a determined wavelength at room temperature. It has been found that the polymer exhibits a weaker antiferromagnetic interaction (J=−2.1 cm−l, μaff=1.68 B.M.) with an apparent spin S<1/2 in the ground state and its conductivity σ298K is 1.01×10−5 S·cm−1 at 13.73 MPa.

Analysis of the pH- and ligand-induced spectral transitions of tryptophanase: activation of the coenzyme at the early steps of the catalytic cycle.

Tryptophanase has an absorption maximum at 338 nm at high pH and 422 nm at low pH. The 422-nm absorption species has been considered to be the catalytically competent ketoenamine form of the Schiff base of pyridoxal 5'-phosphate with a lysine residue. The 338-nm absorption band showed an intense fluorescence band at 390 nm and not around 500 nm, indicating that the 338-nm absorption species is the substituted aldamine rather than an enolimine form of the Schiff base which has been suggested previously. To explore the mechanism of the enzyme that can exert its catalytic ability at high pH where most of its coenzyme exists as the catalytically incompetent aldamine structure, the reaction of tryptophanase with 3-indolepropionate, a substrate analogue that stops the reaction at the step of the Michaelis complex, was studied at various pH values and analogue concentrations. Kinetic analysis was done based on a scheme involving eight forms of the enzyme, i.e., the liganded and unliganded forms of the ketoenamine, the substituted aldamine structures, and their protonated and deprotonated forms. Kinetic parameters were obtained for each interconversion step. The results showed that the binding of 3-indolepropionate to tryptophanase shifts the equilibrium from the substituted aldamine to the ketoenamine structure over the entire pH region studied. This implies that in the reaction of tryptophanase with tryptophan at high pH, where the enzyme shows maximum activity, the binding of the substrate to the enzyme converts the inactive aldamine form of the coenzyme to the active ketoenamine form. Mechanisms for the activation process, in which a nucleophile is expelled from the aldamine either by steric hindrance of the nucleophile with the ligand or by the negative charge of the ligand alpha-carboxylate group that stabilizes the aldimine structure, were discussed.

Anthryloligothienylporphyrins: Energy Transfer and Light-Harvesting Systems

In the new trichromophoric supermolecule 1, a quantitative intramolecular energy transfer (>98 %) occurs from the anthracene donor to the emitting porphyrin acceptor through the oligothiophene chain after selective UV excitation of anthracene. Energy-transfer properties and fluorescence quantum yields are independent of the oligothiophene chain length. Attachment of further anthrylquinquethienyl chromophores to the porphyrin ring results in an increase in the intensity of characteristic absorption and fluorescence bands.