Showing papers in "Luminescence in 2007"

Luminol chemiluminescence catalysed by colloidal platinum nanoparticles

Abstract: Platinum colloids prepared by the reduction of hexachloroplatinic acid with citrate in the presence of different stabilizers were found to enhance the chemiluminescence (CL) of the luminol-H(2)O(2) system, and the most intensive CL signals were obtained with citrate-protected Pt colloids synthesized with citrate as both a reductant and a stabilizer. Light emission was intense and reproducible. Transmission electron microscopy and X-ray photoelectron spectroscopy studies were conducted before and after the CL reaction to investigate the possible CL enhancement mechanism. It is suggested that this CL enhancement is attributed to the catalysis of platinum nanoparticles, which could accelerate the electron-transfer process and facilitate the CL radical generation in aqueous solution. The effects of Pt colloids prepared by the hydroborate reduction were also investigated. The application of the luminol-H(2)O(2)-Pt colloids system was exploited for the determination of compounds such as uric acid, ascorbic acid, phenols and amino acids.

Glowworms: a review of Arachnocampa spp. and kin

Abstract: The term ‘glowworm’ is used in connection with the flightless females of lampyrid fireflies and to describe the luminescent larvae of certain fungus gnats that belong to the subfamilies Arachnocampinae, Keroplatinae and Macrocerinae of the dipteran family Keroplatidae. This review focuses on the luminescent larval fungus gnats. The weakly luminescent species of the Holarctic feed mainly on fungal spores, but some, such as Orfelia fultoni, have turned to a carnivorous diet. Larval Australian and New Zealand Arachnocampa spp. produce brighter in vivo (but not necessarily in vitro) lights, live in cool, damp and dark places and are exclusively predatory. They lure their prey (usually small flying insects) with the help of their blue-green light emissions towards snares consisting of vertical silk threads coated with sticky mucus droplets. Fungus gnats with similar ‘fishing lines’ are found in the Neotropics, but they are not luminescent. The larval stage is longest in the life cycle of Arachnocampa, lasting up to a year, depending on climatic conditions such as temperature and humidity as well as food supply. In A. luminosa, but not the Australian A. flava, female pupae and even female imagines are luminescent. However, it remains to be demonstrated whether it is the light of the female, a pheromone or both that attract the males. Light organs and the chemical reactions to produce light differ between the holarctic and the Australian/New Zealand species. Prey is attracted only by the glowworm's light; odours of the fishing lines or the glowworms themselves are not involved. Recognition of the prey by the glowworm involves mechano- and chemoreception. The eyes of both larval and adult glowworms are large and functional over a spectral range covering UV to green wavelengths. Adults are poor fliers, live only for a few days, have degenerate mouth parts and do not feed. Maintenance of glowworms in captivity is possible and the impact of tourism on glowworms in natural settings can be minimized through appropriate precautions. Copyright © 2007 John Wiley & Sons, Ltd.

Combustion synthesis and luminescence properties of SrAl2O4:Eu2+, Dy3+, Tb3+ phosphor.

Abstract: Eu(2+), Dy(3+) and Tb(3+) co-doped strontium aluminate phosphor with high brightness and long afterglow was synthesized by a combustion method, using urea as a reducer. The properties of SrAl(2)O(4):Eu(2+),Dy(3+),Tb(3+) phosphor with a series of initiating combustion temperatures, urea concentrations and boric acid molar fractions were investigated. The sample at initiating combustion temperature of 600 degrees C exhibited an intense emission peak at 513 nm, in which the phosphor existed as a single-phase monoclinic structure. The experimental results showed that the optimum ratio of urea is 2.0 times higher than theoretical quantities and that the suitable molar fraction of H(3)BO(3) is 0.08. The average particle size of the phosphor was 50-80 nm and its luminescence properties were studied systematically. Compared with SrAl(2)O(4):Eu(2+),Dy(3+) phosphor, the initial luminescence brightness improved from 2.50 candela (cd)/m(2) to 3.55 cd/m(2) and the long afterglow time was prolonged from 1290 s to 2743 s.

Study on the generation mechanism of reactive oxygen species on calcium peroxide by chemiluminescence and UV-visible spectra.

Abstract: In the present work, the generation mechanism of reactive oxygen species (ROS) on calcium peroxide (CaO2,) was studied. A very intense chemiluminescence (CL) signal was observed when adding an aqueous solution of luminol or 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2 alpha]-pyrazin-3-one hydrochloride (MCLA) to a suspension of CaO2. The ROS released on CaO2 were thought to be oxidizing agents leading to CL, and were characterized by CL, UV-visible (UV-vis) spectra and the effective scavengers of the special ROS. From experimental results, the hydroxyl (center dot OH) and superoxide (center dot O-2(-)) radicals were suggested to exist on the surface of CaO2. A reaction scheme for the formation of the ROS on CaO2 was also proposed and discussed. Of more interest was the finding that the CaO2 which released the center dot OH and center dot O-2(-) on the surface exhibited good transition properties compared with alkaline-earth metal peroxides of the same group (MgO2, BaO2). Copyright (c) 2007 John Wiley & Sons, Ltd.

Electrogenerated chemiluminescence of luminol in neutral and alkaline aqueous solutions on a silver nanoparticle self-assembled gold electrode.

Abstract: The electrochemiluminescence (ECL) behaviour of luminol on a silver nanoparticle self-assembled gold electrode in neutral and alkaline solutions was investigated using conventional cyclic voltammetry (CV). The silver nanoparticle self- assembled gold electrode exhibited excellent ECL properties for the luminol ECL system. In neutral solutions, four ECL peaks (ECL-1-ECL-4) were observed at 0.73, 1.15, −0.46 and −1.35 V (vs. SCE), respectively. The intensities of these peaks were enhanced significantly compared with those on a bulk gold electrode and a gold nanoparticle self-assembled gold electrode. It was found that ECL-1 and ECL-2 on a silver nanoparticle-modified electrode were about 1000 and 1770 times stronger than those on a bare Au electrode and were about 17 and 15 times stronger than those on a gold nanoparticle-modified electrode, respectively. In alkaline solutions, four ECL peaks were also observed that were much stronger than those in neutral solutions, and ECL-1 and ECL-2 were enhanced by about three orders and one order of magnitude compared with those on a bare Au electrode and on a gold nanoparticle self-assembled electrode, respectively. Moreover, the silver nanoparticle-modified electrode exhibited good stability and reproducibility for luminol ECL. These peaks were found to depend on a number of factors, including silver nanoparticles on the surface of the modified electrode, potential scan direction, scan rate, scan range, the presence of O2 or N2, pH values, the concentrations of NaBr and luminol, and buffer solutions. The emitter of the ECL was confirmed as 3-aminophthalate by analysing the CL spectra. The surface state of the silver nanoparticle self-assembled electrode was characterized by scanning electron microscopy (SEM) and the interface property of the electrode was studied by electrochemical impedance spectroscopy (EIS). A mechanism for the formation of these ECL peaks is proposed. The results demonstrate that luminol has excellent ECL properties, such as strong ECL intensity and good reproducibility on a silver nanoparticle-modified gold electrode, in both neutral and alkaline solutions, which is of great potential in analytical applications. Copyright © 2006 John Wiley & Sons, Ltd.

The main neutrophil and neutrophil‐related functions may compensate for each other following exercise—a finding from training in university judoists

Abstract: In order to clarify the relationship between exercise and neutrophil function, we measured three major neutrophil and neutrophil-related functions, viz. the reactive oxygen species (ROS) production capability and phagocytic activity (PA) of neutrophils and serum opsonic activity (SOA), simultaneously before and after a unified loading exercise under three different sets of conditions. Thirteen female collegiate judoists were examined with a unified exercise loading (2 h) immediately before and after a 64 day training period. Immediately thereafter, the athletes took part in a 6 day intensified training camp, following which the same exercise loading was repeated. Responses from circulating neutrophils were estimated by comparing the two sets of values obtained before and after the two instances of exercise loading. The parameters assessed included neutrophil count, SOA, PA and ROS production capability. ROS production increased after the exercise loading performed immediately before and after the 64 day training period just before the camp, (p < 0.01) but decreased following the exercise loading performed after the camp (p < 0.05). This suggested depressed bacteriocidal capability of the circulating neutrophils. PA decreased after the exercise loading sessions imposed prior to and after the 64 day training period (p < 0.01) but did not change in the loading session after the camp. No changes were seen in SOA produced with the loading exercise either before the 64 day exercise period or before the camp, but increased significantly following the post-camp session (p < 0.05). In conclusion, athletic training-induced changes in immune functional activities of neutrophils, such as ROS production and PA, and neutrophil-related factors, such as SOA, may compensate for each other to maintain the overall integrity of the neutrophil immune function. Copyright © 2006 John Wiley & Sons, Ltd.

Synthesis of glutathione-capped CdS quantum dots and preliminary studies on protein detection and cell fluorescence image.

Abstract: A series of glutathione (GSH)-capped aqueous CdS quantum dots (QDs) with strong photoluminescence (PL) were prepared by changing the reaction temperatures and times on the basis of optimization of the mole ratio of S to Cd. The reaction time was shortened to about 1/10 compared with that reported previously by increasing the reaction temperature. The absorption and fluorescence spectra indicated good optical properties with PL full width of half-maximum (FWHM) of about 100 nm. The excitation spectrum was broad and continuous in the range 200–480 nm. The PL quantum efficiency (QE) of the prepared QDs was about 36% compared with rhodamine 6G (95%). The shape and size of the CdS QDs were characterized using high-resolution transmission electron microscopy (HRTEM). The prepared QDs were conjugated with bovine serum albumin (BSA) and onion inner pellicle cells and used as fluorescence probes for the first time. The results demonstrated that the fluorescence of CdS can be enhanced by BSA and the enhanced fluorescence intensity is proportional to the concentration of BSA in the range 1.0–10 mg/L. The aggregation of CdS in onion inner pellicle cells and its fluorescence images indicated that the QDs can aggregate around cells soaked for 8 h in CdS solution but enter the interior of cells and become aggregated to the nucleus when they are soaked in CdS solution for longer, e.g. 98 h. Copyright © 2007 John Wiley & Sons, Ltd.

The expression level of luciferase within tumour cells can alter tumour growth upon in vivo bioluminescence imaging.

Abstract: In vivo bioluminescence imaging is becoming a very important tool for the study of a variety of cellular and molecular events or disease processes in living systems. In vivo bioluminescence imaging is based on the detection of light emitted from within an animal. The light is generated as a product of the luciferase-luciferin reaction taking place in a cell. In this study, we implanted mice with tumour cells expressing either a high or a low level of luciferase. In vivo bioluminescence imaging was used to follow tumour progression. Repeated luciferin injection and imaging of high and low luciferase-expressing tumours was performed. While low luciferase-expressing tumours grew similarly to vector controls, growth of the high luciferase-expressing tumours was severely inhibited. The observation that a high level of luciferase expression will inhibit tumour cell growth when an animal is subjected to serial in vivo bioluminescence imaging is potentially an important factor in designing these types of studies.

Bioluminescent assay of total bacterial contamination of drinking water.

Abstract: A bioluminescent assay of total bacterial contamination (TBC) of drinking water (DW) with a detection limit of ∼1 CFU/mL and duration of less than 7 h has been developed. The protocol of the TBC assay comprises: incubation of water sample in nutrition broth supplemented with salts mixture, up to 6 h; filtration of bacterial suspension obtained through membrane filter (pore size 0.45 µm); release of bacterial ATP by dimethyl sulphoxide; determination of bacterial ATP concentration using highly sensitive ATP reagent based on recombinant Luciola mingrelica luciferase. To simplify the assay, special luminometer microcuvette Filtravette™ (New Horizons Diagnostics Corp., USA) are used. A good correlation (R = 0.98) between ATP concentration measured after 6 h incubation and initial bacterial titre in DW was observed. Semi-quantitative TBC assay of DW is also available. The TBC value in DW is assessed by the fixation of incubation time required to detect a measurable bioluminescent signal: 3, 4 and 6 h corresponds to 100–1000, 10–100 and 1–10 CFU/mL, respectively. Copyright © 2007 John Wiley & Sons, Ltd.

Fluorescence resonance energy transfer between two quantum dots with immunocomplexes of antigen and antibody as a bridge

Abstract: In this study, 573 nm quantum dots (QDs)-rabbit IgG–goat anti-rabbit IgG–638 nm QDs immunocomplexes were prepared, utilizing antigen–antibody interaction. 573 nm-emitting QDs were conjugated to antigen (rabbit IgG) and 638 nm-emitting QDs were conjugated to antibody (goat anti-rabbit IgG) via electrostatic/hydrophilic self-assembly, respectively. The mutual affinity of the antigen and antibody brought two kinds of QDs close enough to result in fluorescence resonance energy transfer (FRET) between them; the luminescence emission of 573 nm QDs was quenched, while that of 638 nm QDs was enhanced. The luminescence emission of 573 nm QDs could be recovered when the immunocomplexes were exposed to the unlabelled rabbit IgG antigen. The FRET efficiency (E) and the distance between the donor and the acceptor were calculated. Copyright © 2006 John Wiley & Sons, Ltd.

A bioluminescent signal system: detection of chemical toxicants in water.

Abstract: Prototype technologies of a bioluminescent signal system (BSS) based on the luminous bacterium Photobacterium phosphoreum and three enzymatic bioluminescence systems have been proposed for detecting and signalling the presence of toxicants in water systems. A number of pesticides, mostly known as poisonous substances, similar in their structures and physicochemical properties, have been taken as model compounds of chemical agents. The effect of toxicants (organophosphates, derivatives of dithiocarbamide acid, and pyrethroid preparations) on the bioluminescence of the four systems has been analysed. EC50 and EC80 have been determined and compared to the maximum permissible concentration for each of the analysed substances. The triple-enzyme systems with ADH and trypsin have been shown to be more sensitive to organophosphorous compounds (0.13- 11 mg/L), while the triple-enzyme system with trypsin is highly sensitive to lipotropic poison, a derivative of dithiocarbamine acid (0.03 mg/L). Sensitivities of the triple-enzyme systems to pyrethroid preparations are similar to those of luminous bacteria (0.9- 5 mg/L). The results can be used to construct an alarm-test bioluminescence system for detecting chemical toxicants, based on intact bacteria or enzyme systems. Copyright © 2007 John Wiley & Sons, Ltd.

Determination of trimethylamine in fish by capillary electrophoresis with electrogenerated tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection

Abstract: A capillary electrophoresis with electrogenerated chemiluminescence (CE–ECL) method for the determination of trimethylamine (TMA) in fish was studied. In the presence of TMA, ECL from the reaction of analyte and in situ generated tris(2,2′-bipyridyl)ruthenium(III) [Ru(bpy)33+] at electrode surface could be produced. The ECL detection was performed using a Pt working electrode biased at 1.23 V (vs. Ag/AgCl) potential in a 10 mmol/L sodium borate buffer solution, pH 9.2, containing 3 mmol/L Ru(bpy)32+. A linear calibration curve (correlation coefficient = 0.9996) was obtained in the range 8 × 10−5–4 × 10−8 mol/L for TMA concentration. Recoveries obtained were in the range 98.78–101.46%. The method was successfully applied for the assay of TMA in fish, in combination with solid phase extraction (SPE) disks for sample clean-up and enrichment. Copyright © 2007 John Wiley & Sons, Ltd.

Flow-injection determination of carbaryl and carbofuran based on KMnO4–Na2SO3 chemiluminescence detection

Abstract: A flow-injection method is described for the determination of carbaryl and carbofuran. It was found that a strong chemiluminescence (CL) signal was generated when these pesticides were mixed with Na(2)SO(3) and KMnO(4) in acidic medium. Under the optimum experimental conditions, the enhanced CL intensity was linear, with the concentrations in the range 0.1-2.0 microg/mL (r(2) = 0.9996 and 0.9993, n = 6) with relative standard deviation (n = 4) in the range 1.0-2.3%. The limits of detection (3sigma blank) were 10 and 50 ng/mL, respectively, with a sample throughput of 180/h. The proposed method was applied to determine carbaryl and carbofuran in freshwaters with satisfactory results. Most metal and non-metal ions and some pesticides, such as carbophenothion and aldicarb, do not interfere with the determination. Dinoseb, diazinon and malathion calibration graphs (in the range 0.2-2.0 microg/mL, r(2) = 0.9966-0.9988, n = 6) were also established with relative standard deviations (n = 4) in the range 1.2-2.0% with limits of detection (3sigma blank) in the range 100-300 ng/mL.

Zeolite-based cataluminescence sensor for the selective detection of acetaldehyde.

Abstract: The reactions of acetaldehyde with O atoms in the cages of large-pore zeolites have been discovered to result in light emission. The luminescence characteristics of acetaldehyde vapours passing through the surface of chosen zeolites were studied using a cataluminescence-based detection system. To demonstrate the feasibility of the method, the detection of acetaldehyde using catalysts was studied systematically and a linear response of 0.06–31.2 µg/mL acetaldehyde vapour was obtained. Methanol, ethanol, isopropanol, methylbenzene, chloroform, dichlormethane and acetonitrile did not interfere with the determination of acetaldehyde. Acetaldehyde vapour could also be distinguished from some homologous series such as formaldehyde, cinnamaldehyde, glutaraldehyde and benzaldehyde on this catalyst, possibly due to the stereoselectivity of the zeolite and its specific reaction mechanism. Moreover, acetaldehyde was quantified without detectable interference from formaldehyde in four artificial samples. Thus, this kind of cataluminescence-based sensor could be potentially extended to the analysis of volatile organic compounds in air, and the simple and portable properties of cataluminescence-based sensors could also make them beneficial in many areas of analytical science. Copyright © 2007 John Wiley & Sons, Ltd.

The preparation of CdTe nanoparticles and CdTe nanoparticle-labelled microspheres for biological applications.

Abstract: Different sizes of CdTe semiconductor nanoparticles were prepared in aqueous solution. These nanoparticles exhibit narrow fluorescence with full width at half-maximum (FWHM) of 35-45 nm that spans the visible spectrum, and they also have high PL quantum yield with high resistance to photodegradation. In addition, CdTe quantum dot (QD)-labelled microspheres, comprising polystyrene (PS) cores and CdTe/polyelectrolyte (PE) shells, were also prepared by the layer-by-layer technique in this paper. The optical properties of the CdTe nanoparticles and CdTe-labelled microspheres were investigated by UV-Visible absorption and luminescence spectroscopy, and fluorescence microscopy was employed for microscopic identification behaviour of the luminescent microspheres.

In vitro scavenging activity for reactive oxygen species by N-substituted indole-2-carboxylic acid esters.

Abstract: The hydroxyl radical (HO*)- and superoxide anion radical (O* (2))-scavenging activity, as well as the singlet oxygen ((1)O(2))-quenching property of N-substituted indole-2-carboxylic acid esters (INDs) were investigated by deoxyribose degradation assay, a chemiluminescence method and the electron spin resonance (ESR) spin-trapping technique. This novel group of compounds was developed as a search for cyclooxygenase-2 (COX-2)-selective enzyme inhibitors. The results obtained demonstrated that of the 16 compounds examined, five inhibited light emission from the superoxide anion radical (O* (2))-DMSO system by at least 60% at a concentration of 1 mmol/L, nine prevented the degradation of deoxyribose induced by the Fenton reaction system (range 3-78%) or scavenged hydroxyl radicals (HO*) directly (range 8-93%) and 14 showed the (1)O(2)-quenching effect (range 10-74%). These results indicate that majority of the indole esters tested possess the ability to scavenge O(-) (2) and HO radicals and to quench (1)O(2) directly, and consequently may be considered effective antioxidative agents.

Determination of ibuprofen in pharmaceutical formulations using time-resolved terbium-sensitized luminescence.

Abstract: A sensitive and specific luminescence method for the determination of ibuprofen (IB) in pharmaceutical formulations in aqueous solution is described. The method is based on the luminescence sensitization of terbium (Tb3+) by formation of ternary complex with IB in the presence of tri-n-octylphosphine oxide (TOPO) and Tween-20 as surfactant. The luminescence signal for Tb–IB–TOPO is monitored at λex = 229 nm and λem = 545 nm. Optimum conditions for the formation of the complex in aqueous system, were 16 mmol/L TRIS buffer, pH 5.7, TOPO 200 µmol/L and 15 µmol/L of Tb3+, which allows for the determination of 9.7 × 10−7 – 9.7 × 10−6 mol/L IB with a detection limit of 1.2 × 10−7 mol/L. The relative standard deviations of the method were <1.4%, indicating excellent reproducibility. The proposed method was successfully applied for the assays of IB in pharmaceutical formulations with average recoveries of 100.3–102.5%. Copyright © 2007 John Wiley & Sons, Ltd.

Few substitutions affect the bioluminescence spectra of Phrixotrix (Coleoptera: Phengodidae) luciferases: a site-directed mutagenesis survey.

Abstract: Phrixotrix (railroad worm) luciferases produce bioluminescence in the green and red regions of the spectrum, depending on the location of the lanterns, and are the only luciferases naturally producing red bioluminescence. Comparison of the luciferase sequences showed a set of substitutions that could be involved in bioluminescence colour determination: (a) unique substitutions in the red luciferase replacing otherwise invariant residues; (b) conserved basic residues in the green–yellow emitting luciferases; and (c) an additional R353 residue in red-emitting luciferase (Viviani et al., 1999). To investigate whether these sites have a functional role in bioluminescence colour determination, we performed a site-directed mutagenesis. Natural substitutions in the region 220–344 and residues in the putative luciferin-binding site were also investigated. With the exception of the previously identified substitution of R215 and T226 (Viviani et al., 2002), which display dramatic red-shift effects on the spectrum of green–yellow-emitting luciferases, only a few substitutions had a moderate effect on the spectrum of the green-emitting luciferase. In contrast, no single substitution affected the spectrum of the red-emitting luciferase. The results suggest that the identity of the active site residues is not so critical for determining red bioluminescence in PxRE luciferase. Rather, the conformation assumed during the emitting step could be critical to set up proper interactions with excited oxyluciferin. Copyright © 2007 John Wiley & Sons, Ltd.

Size-dependent fluorescence of dibenzoylmethanate and ditoluylmethanate of boron difluoride.

Abstract: Significant differences in the luminescence properties of dibenzoylmethanate and ditoluylmethanate of boron difluoride bulk crystals and microcrystals were detected. The size-dependent blue-to-green colour change of the luminescence is connected with the band intensity redistribution of monomer and excimer luminescence and fluorescence due to interdimer interaction. Copyright © 2007 John Wiley & Sons, Ltd.

Development of imidazopyrazinone red-chemiluminescent probes for detecting superoxide anions via a chemiluminescence resonance energy transfer method

Abstract: During the development of useful probes for detecting superoxide anions via chemiluminescence with longer wavelengths than that of green, chemiluminescent probes that emit red light (λmax 610 nm) when induced by superoxide anions were synthesized and characterized. These red-chemiluminescent probes consist of a 6-(4-methoxyphenyl)imidazo[1,2-a] pyrazin-3(7H)-one moiety, which reacts with superoxide anions to generate energy, and a sulphorhodamine 101 moiety, which accepts the energy and emits red light. Using a hypoxanthine–xanthine oxidase system for the generation of superoxide anions, it was shown that the superoxide anion-induced chemiluminescences of red-chemiluminescent probes (3 and 4) were more intense than those of the blue- and green-chemiluminescent probes 2-methyl-6-(4-methoxyphenyl)imidazo[1,2-a] pyrazin-3(7H)-one (MCLA) and 6-[4-[2-[N′-(5-fluoresceinyl)thioureido]-ethoxy]phenyl]-2-methylimidazo[1,2-a]pyrazin-3(7H)-one (FCLA), respectively, which are generally considered to be the most sensitive chemiluminescent probes. The ratio between the superoxide-dependent and background chemiluminescence intensities for 3 was comparable to those of MCLA and FCLA, but higher than that of 4. Due to its highly intense superoxide anion-induced chemiluminescence at low probe concentrations, red-chemiluminescent probe 3 is superior to MCLA and FCLA for measurement of superoxide anions. Copyright © 2006 John Wiley & Sons, Ltd.

Studies on the interaction between tetraphenylporphyrin compounds and bovine serum albumin.

Abstract: The interaction of three porphyrin compounds with bovine serum albumin (BSA) was examined by fluorescence emission spectra at the excitation wavelength 280 nm and in UV-Vis absorption spectra. Through fluorescence quenching experiments, it was confirmed that the combination of three porphyrin compounds with BSA was a single static quenching process. The binding constant KA, the thermodynamic parameters enthalpy change (ΔH0), Gibbs free energy change (ΔG0) and entropy change (ΔS0) were obtained. It was found that hydrophobic interaction played a main role in tetraphenylporphyrin (TPP) or tetraparacholophenylporphyrin (TClPP) binding to BSA, while tetraparamethoxyphenylporphyrin (TMEOPP) mainly based on van der Waals' force. According to Foster energy transfer, the separate distance r, the energy transfer efficiency E and Foster radium R0 were calculated. The results obtained from the above experiments showed that three porphyrin compounds were tightly bound to BSA. Copyright © 2007 John Wiley & Sons, Ltd.

Fluorescence and bioluminescence analysis of sequential UV-biological degradation of p-cresol in water.

Abstract: The photolysis and Penicillium tardum H-2 degradation of p-cresol in water containing humic acids was investigated by fluorescence and bioluminescence methods. Humic acids extracted from peat (the Vasuygan bog, Tomsk region of Russia) induce the phototransformation of p-cresol. The influence of humic acids on the phototransformation of p-cresol under different irradiation conditions was investigated. Comparison of the data on the KrCl* (λ = 222 nm) and XeCl* (λ = 308 nm) excilamps light showed that the most effective p-cresol degradation was observed with mercury lamp irradiation in the presence of humic acids. Copyright © 2006 John Wiley & Sons, Ltd.

Homogeneous electrogenerated chemiluminescence immunoassay for the determination of digoxin employing Ru(bpy)(2)(dcbpy)NHS and carrier protein.

Abstract: A highly sensitive homogeneous electrogenerated chemiluminescence (ECL) immunoassay for the determination of anti-digoxin antibody and digoxin hapten was developed employing Ru(bpy)2(dcbpy)NHS (bpy = 2,2′-bipyridyl; dcbpy = 2,2′-bipyridine-4,4′-dicarboxylic acid; NHS = N-hydroxysuccinimide ester) as an electrochemiluminescent label and bovine serum albumin (BSA) as a carrier protein. A digoxin hapten was indirectly heavily labelled with Ru(bpy)2(dcbpy)NHS through BSA to form Ru(bpy)2(dcbpy)NHS–BSA–digoxin conjugate. The ECL intensity of the immunocomplex of the conjugate with anti-digoxin antibody markedly decreased when the immunoreaction between Ru(bpy)2(dcbpy)NHS–BSA–digoxin conjugate and anti-digoxin antibody took place. Two formats, direct homogeneous immunoassay for anti-digoxin antibody and competitive immunoassay for digoxin, were developed to determine anti-digoxin antibody and digoxin, respectively. The anti-digoxin antibody concentration in the range 7.6 × 10−8–7.6 × 10−6 g/mL was determined by direct homogeneous format. Digoxin hapten was determined throughout the range 4.0 × 10−10–1.0 × 10−7 g/mL with a detection limit of 1.0 × 10−10 g/mL by competitive format. The relative standard derivation for 6.0 × 10−9 g/mL was 4.3%. The method has been applied to assaying digoxin in control human serum. Copyright © 2006 John Wiley & Sons, Ltd.

The effect of high-temperature annealing on optical properties of porous anodic alumina formed in oxalic acid.

Abstract: Photoluminescence (PL) of anodic alumina membranes (AAMs) with ordered nanopore arrays fabricated in oxalic acid has been investigated under different annealing temperatures. X-ray diffraction reveals the structural transition from the amorphous state to crystallization. PL measurements show that a blue PL band occurs in the wavelength range 300–600 nm. The differential thermal analysis (DTA) and thermogravimetric analysis (TG) results revealed plentiful oxalic ions incorporated into the prepared AAMs. The PL band of AAMs could be attributed to the co-actions of the oxygen vacancies (F+ and F centres) and the luminescent centres transformed from oxalic impurities. With the increase of the annealing temperature, the intensities of PL increase first, and at 500°C reach a maximum value, then decrease. The PL phenomenon is intimately related to the temperature-induced structural transitions. There are three optical centres in the annealed AAMs; the first is originates from the F centres, the second is correlated with F+ centres and the third is associated with the oxalic impurities incorporated in the AAMs. Copyright © 2007 John Wiley & Sons, Ltd.

Flow-injection–electrochemical oxidation fluorimetry for determination of methotrexate

Abstract: A novel fluorimetric model of on-line electrochemical oxidation for the determination of methotrexate (MTX) is described in this paper. The method was based on the oxidation of MTX to a highly fluorescent product, 2,4-diaminopteridine-6-carboxylic acid, by constant potential in the electrochemical oxidation flow cell. Stopped-flow techniques were employed. Under optimal conditions, the fluorescence intensity of 2,4-diaminopteridine-6-carboxylic acid was measured at excitation and emission wavelengths of 380 and 465 nm, respectively. The calibration graph was linear over concentrations of methotrexate in the range 2.0 × 10−7–1.0 × 10−5 g/mL, with a detection limit of 5.2 × 10−8 g/mL (3σ). The method has been successfully applied to the determination of methotrexate in human urine samples and showed a percentage recovery in the range 94.3–102.5%. Copyright © 2007 John Wiley & Sons, Ltd.

A flow-injection chemiluminescence method for the determination of human serum albumin, using the reaction of fluorescein-human serum albumin-sodium hypochlorite by the enhancement effect of the cationic surfactant cetyltrimethylammonium bromide.

Abstract: The interaction between surfactant and fluorescein was studied, using a fluorescence spectroscopy and flow-injection (FI) chemiluminescence (CL) method It was found that the cationic surfactant cetyltrimethylammonium bromide (CTAB) could cause the structural transformation of fluorescein from the quinone to the spirolactone form, and greatly enhance the CL intensity of the fluorescein-human serum albumin (HSA) complex Based on this finding, a rapid and sensitive FI-CL method was developed for the determination of HSA Under the optimum conditions, the proposed method has a linear range of 005-240 microg/mL, with a detection limit of 003 microg/mL for HSA (3sigma) The relative standard deviation (RSD) of 12 microg/mL HSA (n = 8) is 08% The method was applied to the determination of protein content in urine samples, with satisfactory results Density functional theory was used to study the mechanism of surfactant-enhanced CL intensity of the fluorescein-HSA complex

Electrochemiluminescence determination of codeine or morphine with an organically modified silicate film immobilizing Ru(bpy)32

Abstract: An ECL approach was developed for the determination of codeine or morphine based on tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+) immobilized in organically modified silicates (ORMOSILs). Tetramethoxysilane (TMOS) and dimethyldimethoxysilane (DiMe-DiMOS) were selected as co-precursors for ORMOSILs, which were then immobilized on a surface of glassy carbon electrode (GCE) by a dip-coating process. Ru(bpy)32+ was immobilized in the ORMOSIL film via ion-association with poly(p-styrenesulphonate). The ORMOSIL-modified GCE presented good electrochemical and photochemical activities. In a flow system, the eluted codeine or morphine was oxidized on the modified GCE and reacted with immobilized Ru(bpy)32+ at a potential of +1.20 V (vs. Ag/AgCl). The modified electrode was used for the ECL determination of codeine or morphine and showed high sensitivity. The calibration curves were linear in the range 2 × 10−8–5 × 10−5 mol/L for codeine and 1 × 10−7–3 × 10−4 mol/L for morphine. The detection limit was 5 × 10−9 mol/L for codeine and 3 × 10−8 mol/L for morphine, at signal:noise ratio (S:N) = 3. Both codeine and morphine showed reproducibility with RSD values <2.5% at 1.0 × 10−6 mol/L. Furthermore, the modified electrode immobilized Ru(bpy)32+ was applied to the ECL determination of codeine or morphine in incitant samples. Copyright © 2007 John Wiley & Sons, Ltd.

Quantitative determination of bilirubin by inhibition of chemiluminescence from lucigenin.

Abstract: Bilirubin is a metabolic breakdown product of blood haem, of great biological and diagnostic importance. A new chemiluminescence (CL) method has been developed for the quantification of bilirubin. The method is combined with the flow injection analysis (FIA) technique and based on the inhibition effect of bilirubin on the CL from the lucigenin–hydrogen peroxide system in an alkaline medium. Under the optimum conditions, the decreased CL intensity was proportional to the concentration of bilirubin, in the range 0.0585–58.47 µg/mL. The detection limit estimated from the calibration graph was about 7.8826 ng/mL. The relative standard deviation (RSD) of 10 parallel measurements (1 × 10−4 mol/L bilirubin) was 2.5%. Recoveries of bilirubin were found to fall in the range 94–97.5% using control sera. The method is interference-free, fast and easy to carry out. Copyright © 2007 John Wiley & Sons, Ltd.

Bioluminescence characteristics of a tropical terrestrial fungus (Basidiomycetes).

Abstract: Freshly collected samples of luminous mycelium of a terrestrial fungus from Panama were investigated for their bioluminescence characteristics. Taxonomic identification of fungal species could not be determined because of the lack of fruiting bodies. Fluorescence excited by 380 nm illumination had an emission spectrum with a main peak at 480 nm and additional chlorophyll peaks related to the wood substrate. Bioluminescence appeared as a continuous glow that did not show any diel varia- tion. The light production was sensitive to temperature and decreased with temperatures higher or lower than ambient. Bioluminescence intensity was sensitive to hydration, increasing by a factor of 400 immediately after exposure to water and increasing by a factor of 1 million after several hours. This increase may have occurred through dilution of superoxide dismutase, which is a suppressive factor of bioluminescence in fungus tissue. The mycelium typically transports nutritive substances back to the fruiting body. The function of luminescent mycelium may be to increase the intensity of light from the fungus and more effec- tively attract nocturnal insects and other animals that serve as disseminating vectors for fungal spores. Copyright © 2007 John Wiley & Sons, Ltd.

Time-resolved chemiluminescence study of the TiO2 photocatalytic reaction and its induced active oxygen species.

Abstract: The time-resolved chemiluminescence (CL) method has been applied to study the TiO(2) photocatalytic reaction on a micros-ms timescale. The experimental set-up for time-resolved CL was improved for confirmation of the unique luminol CL induced by the photocatalytic reaction. The third harmonic light (355 nm) from an Nd:YAG laser was used for the light source of the TiO(2) photocatalytic reaction. Luminol CL induced by this reaction was detected by a photomultiplier tube (PMT) and a preamplifier was used for amplifying the CL signal. Experimental conditions affecting the photocatalytically induced CL were discussed in detail. The involvement of active oxygen species such as .OH, O(2) (.-) and H(2)O(2) in the CL was examined by adding their scavengers. It is concluded that .OH was greatly involved in the CL on a micros-ms timescale, especially in time periods <100 micros after illumination of the pulse laser. On the other hand, CL generated by O(2) (.-) began to increase after 100 micros and became dominant after 2.5 ms. A small part of the CL might be generated by H(2)O(2) on the whole micros-ms timescale. A CL reaction mechanism related with .OH and dissolved oxygen was proposed to explain the photocatalytically induced luminol CL on a micros-ms timescale, especially in periods <100 micros.