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PubMedDate not supplied

Application of functional group modified substrate in room-temperature phosphorescence, I--beta-cyclodextrin modified paper substrate for enrichment and determination of fluorene and acenaphthene.

A novel method for the determination of fluorene and acenaphthene on solid phase extraction-room-temperature phosphorescence (SPE-RTP) was studied. beta-cyclodextrin (beta-CD) was chemically bonded onto chromatography paper by reaction with epichorohydrin in an ultrasonic bath. The RTP signal of fluorene and acenaphthene included on the beta-CD-modified paper was increased more than 10 times compared with non-modified filter paper, indicating the formation of the inclusion complex. The conditions for the of RTP of compounds were studied in detail. The linear ranges of fluorene and acenaphthene concentrations to the RTP intensity were over two orders of magnitude (8.0 x 10(-7)-4.0 x 10(-5) mol/L for fluorene) with a correlation coefficient of 0.999. The concentration limits of detection for fluorene and acenaphthene were 1.11 x 10(-8) mol/L and 3.8 x 10(-7) mo/L, respectively. When the sampling volume was 10 microL, the absolute LODs for fluorene and acenaphthene were 18.4 pg/spot and 0.58 ng/spot, respectively. The modified filter paper was used for solid phase extraction (SPE) and the retention behaviour of fluorene and acenaphthene was examined. The enrichment efficiency of the analytes was higher than 100-fold. The SPE-RTP coupling technique was applied directly to the determination of fluorene and acenaphthnene in environmental water samples.

Acenaphthenes↗

PubMedDate not supplied

Application of functional group modified substrate in room temperature phosphorescence, II--heavy atom-chelated filter paper for selective determination of alpha-naphthalene acetic acid.

Heavy atom-chelated filter paper was synthesized and used as the substrate for room-temperature phosphorescence (RTP). The synthesis conditions for chelated paper were studied. The Pb-chelated filter paper could selectively induce the RTP of alpha-naphthalene acetic acid (alpha-NAA). The excitation and emission wavelengths of RTP of alpha-NAA were 300 nm and 521 nm, respectively. The concentration of alpha-NAA was linear with the RTP intensity in the range 2 x 10(-6)-6 x 10(-4) mol/L (correlation coefficient, 0.9999). The concentration detection limit was 1.35 x 10(-7) mol/L and the absolute detection limit was 0.25 ng/spot. The RSD (n = 10) was 1.7%. The method was applied to the analysis of water and vegetable samples with satisfactory results. Because the heavy atom was directly chelated onto the filter paper, the heavy-atom effect on the RTP of NAA was further increased and the analysis procedure was simple, fast and economical.

Aspartic Acid↗

PubMed2006

Synthetically tailored excited states: phosphorescent, cyclometalated iridium(III) complexes and their applications.

Phosphorescent iridium(III) complexes are being widely explored for their utility in diverse photophysical applications. The performance of these materials in such roles depends heavily on their excited-state properties, which can be tuned through ligand and substituent effects. This concept article focuses on methods for synthetically tailoring the properties of bis-cyclometalated iridium(III) materials, and explores the factors governing the nature of their lowest excited state.

Journal Article↗

PubMed2007

Phosphorescent dyes for organic light-emitting diodes.

This article presents general concepts that have guided important developments in our recent research progress regarding room-temperature phosphorescent dyes and their potential applications. We first elaborate the theoretical background for emissive metal complexes and the strategic design of the chelating C-linked 2-pyridylazolate ligands, followed by their feasibility in functionalization and modification in an aim to fine-tune the chemical and photophysical properties. Subsequently, incorporation of 2-pyridylazolate chromophores is illustrated in the synthesis of the highly emissive, charge-neutral Os, Ru, Ir, and Pt complexes. Insights into their photophysical properties are gained from spectroscopy, relaxation dynamics, and theoretical approaches, from which the lowest-lying excited states, competitive radiative decay, and radiationless processes are then analyzed in detail. In view of applications, their potentials for OLEDs have been evaluated. The results, in combination with the fundamental basis, give a conceptual design contributed to the future advances in the field of OLEDs.

Journal Article↗

PubMed1994

Universal phosphorescence immunoassay.

The aim of this study is to develop a universal phosphorescence immunoassay method using monoclonal antibodies to Pd-coproporphyrin (Pd-CP) and conjugates of various proteins with Pd-CP. Pd-CP and monoclonal antibodies obtained allow a convenient method for the determination of various antigens to be developed. The conditions for immunological reactions with Pd-CP were optimized with respect to the components affecting the nonspecific binding Pd-CP and Pd-CP conjugates.

Animals↗

PubMed1999

Pressure/temperature effects on protein flexibilty from acrylamide quenching of protein phosphorescence.

Pressure is an effective modulator of protein structure and biological function. The influence of hydrostatic pressure (</=3 kbar, 10-50 degrees C) on conformational dynamics was assessed from the rate of migration of acrylamide through the protein interior. Migration rates in apoazurin, alcohol dehydrogenase and alkaline phosphatase were obtained from the phosphorescence quenching rate constant (kq) of the deeply buried Trp residues. The dominant effect of applied pressure is to slow the diffusion process, although at low temperature, high pressure may also accelerate it. For apoazurin, alcohol dehydrogenase and alkaline phosphatase the activation free volumes, DeltaV(obs), derived from the pressure-dependence of kq, ranges from +10, +16 and +20 ml mol(-1)at 50 degrees C to -20, +5 and 0 ml mol(-1)at 10 degrees C, respectively. Analysing DeltaV(obs) in terms of a positive contribution from cavity expansion and a negative one from peptide hydration, the results emphasise that whereas at warm temperature the formation of cavities plays a dominant role in the migration process, at low temperature the required flexibility may be conferred by internal protein hydration. The relatively small magnitude of both DeltaV(obs) and the activation enthalpy (DeltaH=10-20 kcal mol(-1)) indicates that acrylamide diffusion jumps inside these proteins appear to involve relatively small amplitude structural fluctuations not requiring major unfolding-like transitions. The implication of these findings for the thermodynamic stability of proteins under pressure is discussed.

Acrylamide↗

PubMed1993

Optical oxygen sensor based on phosphorescence lifetime quenching and employing a polymer immobilised metalloporphyrin probe. Part 2. Sensor membranes and results.

A gaseous oxygen sensor is described based on the measurement of phosphorescence lifetime of the dye palladium coproporphyrin, immobilised in a range of membrane materials including polyvinyl chloride, polymethylmethacrylate, polystyrene and silicone rubber. The lifetime of the dye in these materials is described, measured using a simple system consisting of a pulsed xenon flash lamp light source and a PC-based data acquisition system. The linearity of the sensing membranes over the 0-100 per cent oxygen range is presented together with data on temperature sensitivity, the effects of CO2, N2O, H2O and halothane, and the effects of ageing over a 90 day period. The sensors based upon polystyrene immobilised dye appear to provide the optimum characteristics for a gaseous oxygen sensor.

Humans↗

PubMed2001

Solid-substrate room-temperature phosphorescence study on zinc(II) and tin(IV) protoporphyrins and their interaction with DNA.

The solid-substrate room-temperature phosphorescence (SS-RTP) of two commercially available metalloporphyrin compounds, zinc(II) protoporphyrin (ZnPP) and tin(IV) protoporphyrin (SnPP) has been studied. Strong and stable RTP signals of the two metalloporphyrins in neutral to weakly basic solutions can be simply induced on filter paper without addition of external heavy atom perturbers. Their emission bands appeared at 723 nm for ZnPP and 718 nm for SnPP at an excitation wavelength of 417 nm. Compared with SnPP, ZnPP is a better RTP probe for DNA because its RTP enhancement effect is much higher under the same experimental conditions. The interaction of ZnPP with DNA at pH 8.5 gives an apparent binding constant of 9.1 x 10(3) which is similar to that of the cationic porphyrin absorption probe CuTMPyP (copper (II)- tetrakis(4-N-methylpyridyl)porphine complex). Hydrogen bonding between the monocarboxylic acid substituent of ZnPP and the base pairs of DNA plays a crucial role in the binding.

DNA↗

PubMed1990

Phosphorescent zinc sulfide is a nonradioactive alternative for marking autoradiograms.

Phosphorescent zinc sulfide is a nonradioactive alternative for making orientation and identification markings on autoradiograms. Measurements with a luminometer show that light emission is linear with respect to ZnS concentration. A minimum activation time of 5 s has been determined, using an incandescent lamp as a light source. Emission decay kinetics show light emissions reached background levels within minutes, depending on the ZnS concentration. This time period is sufficient for X-ray films to be permanently marked. Because of its efficiency and nontoxicity, this autoradiogram marker could be extremely useful in many protocols, including high-throughput radioactive DNA sequencing. This nonradioactive marker will also be useful in protocols utilizing nonradioactive detection systems, such as those calling for biotinylated and chemiluminescent probes.

Autoradiography↗

PubMed1991

Direct observation of singlet oxygen phosphorescence at 1270 nm from L1210 leukemia cells exposed to polyporphyrin and light.

Near-infrared emission (1170-1475 nm) was studied from L1210 leukemia cells incubated with polyporphyrin (fractionated hematoporphyrin derivative), suspended in deuterium oxide buffer, and then exposed to light. Following pulsed laser excitation, the near-infrared emission decayed in two phases. The first phase of the emission (0-2 microseconds) was principally due to polyporphyrin fluorescence. The second phase of the emission (20-90 microseconds) was due mainly to singlet oxygen. Evidence supporting the assignment of the second phase emission to singlet oxygen included a spectral analysis showing a peak near 1270 nm and reductions in the second phase emission caused by the singlet oxygen quenchers, histidine, carnosine, and water. The second phase emission decayed in a biexponential manner with lifetimes of 4.5 +/- 0.5 and 49 +/- 4 microseconds. Most of the singlet oxygen in the second phase emission was likely due to singlet oxygen that was generated near the surface of the L1210 leukemia cells and then diffused into the deuterium oxide buffer. Direct measurements of singlet oxygen phosphorescence at 1270 nm may prove to be a useful analytical technique for studying photochemical generation of singlet oxygen in cultured cells.

Animals↗

PubMed1992

alpha-Bungarotoxin binding to two acetylcholine receptor alpha-peptides and their methylmercury-modified analogs: intrinsic phosphorescence and optically detected magnetic resonance studies.

Phosphorescence and optically detected magnetic resonance (ODMR) have been used to characterize two synthetic peptides, alpha 181-198 and alpha 185-196, of the major binding determinant of the alpha-acetylcholine receptor (AChR) of Torpedo californica and its interaction with alpha-bungarotoxin (BgTX) using Trp as an intrinsic probe. BgTX conformational changes are suggested upon complexation with the peptides. Methylmercury-modified peptides show conformational heterogeneity which brings some of the modified Cys residues into proximity of peptide Trp(s). These modified peptides, when bound to BgTX, undergo structural changes which remove the tagged Cys from its close contact with the Trp residue(s) of the peptide.

Amino Acid Sequence↗

PubMed1994

Nitric oxide diffusion coefficients in solutions, proteins and membranes determined by phosphorescence.

The reactivity of nitric oxide under a given condition is a complex function of its diffusivity and the concentration of reacting partners. Quenching by NO of luminescence from Ru and Pd chelates of mesoporphyrin IX, two molecules which exhibit phosphorescence at room temperature, was utilized to evaluate the gas concentration and apparent diffusion coefficients. The properties of Ru-mesoporphyrin, a dye not previously employed as a probe for O2 or NO, were determined and the assay was verified and used to quantify NO produced by decomposition of nitrosocysteine. The pseudo-second order quenching constants were obtained from Stern-Volmer plots measured under various conditions and used to calculate diffusion coefficients for nitric oxide in solutions, proteins and membranes. The diffusion coefficients were greater at 37 than at 25 degrees C and, at a given temperature, smaller in proteins and membranes than in water. The conclusion is that NO and O2 closely resemble each other in diffusivity but that NO is slightly less lipophilic, resulting in somewhat faster apparent diffusion in protein and slower diffusivity in lipid, relative to O2. Taking a mean diffusion coefficient for NO of 10(-7) cm2s-1, then within 10 s the mean path is 10(-3) cm, or less than the diameter of a single cell. However, at low NO and O2 concentrations, the halflife of NO will be considerably longer than 10 s, and consequently the path of NO diffusion much greater.

Animals↗

PubMed1988

Phosphorescence of adenosine and poly(riboadenylic acid). Evidence for dual emissions and n pi states.

Phosphorescence from the 9-adenylyl group in the form of microcrystalline powders of adenosine films of poly(riboadenylic acid) (poly(rA)) in hyaluronic acid has been studied at 77 K. For adenosine, clearly resolved vibronic structure consists of two progressions, A and B, with delta vA = 1363 cm-1 and delta vB = 1575 cm-1, correlated with in-plane C5-N7 and in-plane C4-C5 stretch, respectively. The relative strength of the progressions varies with excitation wavelength and this, together with the absence of a common origin, indicates the existence of two independent emitting states with 0-0' levels separated by either 300 or 1000 cm-1. Two different excitation spectra are observed lying below the normal (pi pi*) adsorption and one is assigned as a previously undetected 1(n pi*) transition. For poly(rA) films the emission band envelope is identical with that of adenosine but the vibronic structure is lost. Only one excitation peak is observed at 32.9 X 10(3) cm-1, identical with one of the adenosine spectra. The second adenosine excitation spectrum probably represents an intermolecular charge transfer transition. Comparison is made with the predictions of six semi-empirical MO calculations.

Adenosine↗

PubMed1994

Heterogeneity of protein conformation in solution from the lifetime of tryptophan phosphorescence.

The decay of Trp phosphorescence of proteins in fluid solutions was shown to provide a sensitive tool for probing the conformational homogeneity of these macromolecules in the millisecond to second time scale. Upon examination of 15 single Trp emitting proteins multiexponential decays were observed in 12 cases, a demonstration that the presence of slowly interconverting conformers in solution is more the norm rather than an exception. The amplitude of preexponential terms, from which the conformer equilibrium is derived, was found to be a sensitive function of solvent composition (buffer, pH, ionic strength and glycerol cosolvent), temperature, and complex formation with substrates and cofactors. In many cases, raising the temperature, a point is reached at which the decay becomes practically monoexponential, meaning that conformer interconversion rates have become commensurate with the triplet lifetime. Estimation of activation free energy barriers to interconversion shows that the large values of DeltaG* are rather similar among polypeptides and that the protein substates involved are sufficiently long-lived to display individual binding/catalytic properties.

Journal Article↗

PubMed1986

Room temperature phosphorescence of diazepam and its application to the determination of diazepam in serum and in a tablet formulation.

The room temperature phosphorescence (RTP) properties of diazepam were investigated. The filter papers Whatman No. 1, DE-81 and P-81 were tested as substrates and compounds of I(-), Tl(I), Ag(I), Pb(II) and Hg(II) were evaluated as heavy atom enhancers. The RTP of diazepam spotted from neutral (pH approximately 6.2) and acidic (pH approximately 1.6) solutions were compared. The largest RTP signal for diazepam was obtained from Whatman No. 1 in the presence of Hg(II) in an acidic environment. The absolute limits of detection ranged from 0.5 to 1.9 ng depending on the experimental conditions. RTP was evaluated as a simple, rapid and sensitive screening method for toxic levels of diazepam in serum and for the analysis of diazepam in pharmaceutical formulation (tablets).

Journal Article↗

PubMed1989

Low- and room-temperature phosphorescence characteristics of some pharmaceutical compounds.

Phosphorescence spectral characteristics, lifetimes and limits of detection of 30 pharmaceutical compounds are examined. A particular study on eight phenothiazine derivatives is carried out. Low and room temperature data obtained using an ethanol:water 80:20 glass substrate and a filter paper substrate, respectively, are compared. Lifetimes are corrected for the time constant of the measurement circuit.

Indicators and Reagents↗

PubMed2005

Homogeneous assays for cellular proteases employing the platinum(II)-coproporphyrin label and time-resolved phosphorescence.

Phosphorescent platinum(II) coproporphyrin label (PtCP) is evaluated for the detection of cellular proteases by time-resolved fluorescence in homogeneous format. An octameric peptide containing the recognition motif for the caspase-3 enzyme was dual labeled with a new maleimide derivative of PtCP and with the dark quencher dabcyl. Following photophysical characterization, the quenched substrate was employed in cleavage assays for caspase-3 using Jurkat and HL60 cell lines treated with proapoptotic stimuli performed on a commercial plate reader. Dose-response and time course assays for the drug camptothecin were obtained for comparison with conventional fluorometric detection.

Camptothecin↗

PubMed2005

Molecular imprinted ormosils for nafcillin recognition by room temperature phosphorescence optosensing.

Nafcillin imprinted sol-gels were used as specific binding materials for the room temperature phosphorescence (RTP) recognition of nafcillin using a flow injection system. Selective and reversible binding of the template to imprinted sol-gels could be observed by tailoring the hydrophobic/hydrophilic balance of the materials. Also, the possibility of minimizing non-specific interactions was evaluated by end-capping with trimethyl silyl groups. Control experiments were performed with non imprinted reference sol-gels. The recognition mechanism and the analytical potential of these materials for developing stable, selective and sensitive approaches for nafcillin recognition in real samples are outlined.

Biosensing Techniques↗