Terbium Fluorescence Research Articles

Synthesis and Fluorescence Properties of New Europium (III) and Terbium (III) Complexes with N-(3-methoxyl–phenyl)ketoacetamide

Aβ-diketonate-type ligand, N-(3-methoxyl–phenyl)ketoacetamide (L), and its complexes with europium (III) and terbium (III) were synthesized. The ligand and complexes were characterized by elemental analysis, IR spectra,1HNMR spectra, mass spectra and luminescent spectra. The complexes were characterized by elemental analysis, IR spectra. The stoichiometry of metal-to-ligand in the complexes also was confirmed by the fluorescence behavior of the ligand and complexes in CH3CH2OH solution. In addition, the fluorescence properties of complexes in DMF, CH3OH, CH3CH2OH, acetone and CHCl3were investigated. The characteristic fluorescence of terbium (III) was assigned.

Terbium‐sensitized fluorescence method for the determination of deferasirox in biological fluids and tablet formulation

A novel, rapid and sensitive spectroflurimetric method was developed and validated for the determination of deferasirox in urine, serum and tablet samples based on sensitization of terbium fluorescence. The excitation and emission wavelengths were 328 and 545 nm, respectively. The optimum conditions for the determination of deferasirox were investigated considering the effects of various parameters. The method was quantitatively evaluated in terms of linearity, recovery, reproducibility and limit of detection. Under the optimal conditions, the fluorescence intensities were linear with the concentration of deferasirox in the range of 5 × 10(-9) to 5×10(-6) mol L(-1) , with a detection limit of 1.5 × 10(-9) mol L(-1) and a relative standard deviation of 1.1-2.3%. Linearity, reproducibility, recovery and limit of detection made the method suitable for determination of deferasirox in urine, serum and tablets samples.

Method for determination of fluoroquinolones based on the plasmonic interaction between their fluorescent terbium complexes and silver nanoparticles

We report on a fluorometric method for the determination of the fluoroquinolones levofloxacin (LEV) and moxifloxacin (MOXI). It is based on the Tb(III)-sensitized luminescence that is plasmonically enhanced by silver nanoparticles (Ag NPs). The emission of the Tb(III) complexes has maximum at 545 nm after excitation at 284 nm and is strongly enhanced in the presence of the colloidal Ag NPs. Under optimum experimental conditions, luminescence intensity increases linearly with the concentration in the range from 4.16 × 10-17-3.59 × 10-15 M of LEV, and from 4.98 × 10-17-2.49 × 10-15 M for MOXI with correlation coefficients of 0.9996 and 0.9996, respectively. The limits of detection are 7.19 × 10-18 M and 8.47 × 10-18 M, respectively, and the relative standard deviations are 1.3 and 1.5% for 5 replicate measurements at 6.08 × 10-14 M of LEV and 5.48 × 10-14 M of MOXI. The method was successfully applied to the determination of LEV and MOXI in pharmaceutical samples, in urine and in serum.

Terbium, a fluorescent probe for investigation of siderophore pyochelin interactions with its outer membrane transporter FptA

Pyochelin (Pch) is a siderophore and FptA is its outer membrane transporter produced by Pseudomonas aeruginosa to import iron. The fluorescence of the element terbium is affected by coordinated ligands and it can therefore be used as a probe to investigate the pyochelin–iron uptake pathway in P. aeruginosa. At pH 8.0, terbium fluorescence is greatly enhanced in the presence of pyochelin indicating chelation of the metal by the siderophore. Titration curves showed a 2:1 (Pch:Tb 3+) stoichiometry and an affinity of K =( 2 ± – 1 )× 10 11 M − 2 was determined. Pch–Tb interaction with the transporter FptA could be followed in vitro and in vivo in P. aeruginosa cells, by Fluorescence Resonance Energy Transfer (FRET) between three partners: the tryptophans of FptA (donor), Pch (acceptor for the Trps and donor for Tb 3+) and Tb 3+ (acceptor). Pch–Tb binds to the Pch–Fe outer membrane transporter FptA with a dissociation constant (K d) of 4.6 μM. This three-partner FRET is a potentially valuable tool for investigation of the interactions between FptA and its siderophore Pch.

Fluorimetric assay of flumequine using sensitized terbium fluorescence in organized media

The effects of second ligands, micellar surfactant solutions, and microemulsions on the sensitized fluorescence signal from a chelate of Tb3+ with flumequine (FL) were studied. The presence of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline in a microemulsified medium of the “oil in water” type produced a six-fold increase in the sensitized fluorescence signal from the binary chelate of Tb3+ and FL. 1,10-Phenanthroline as a second ligand and micellar solutions of anionic surfactants increased emissions by a factor of 4.4 at pH 7.0. The latter system was used to develop a fluorimetric assay for flumequine operating over the concentration range 2.6 × 10−9to 0.26 × 10−6g/ml, R 2 = 0.997, with a detection limit of 1.3 × 10−9g/ml.

Coping with the Environment: How Microbes Survive Environmental Challenges

Microorganisms are exposed to constantly changing environments in their natural habitats either in planktonic form or microbial communities. Examples of these environmental changes encompass nutrient limitation, temperature, pH, and osmolarity fluctuations, radiation, and other harmful agents, such as excessive amount of superoxides and heavy metals. To respond and adapt to adverse environmental changes, microorganisms employ a striking combination of transcriptional regulatory circuits to sense and translate extracellular stimuli into specific cellular signals, resulting in altered gene expression and protein activities. Investigation of these underlying mechanisms and strategies could improve our understanding of microbial physiology in general and potentially lead to discoveries of practical value in the field of health care and environment protection. In this special issue, we have invited a few papers that explore this topic from various perspectives. The first paper “Exposure to glycolytic carbon sources reveals a novel layer of regulation for the MalT regulon” presents the study on a synthetic lethal mutant ompR malTcon of Escherichia coli in which the constitutively expressed maltose system regulator MalT in its active form causes cell death in the absence of the osmoregulator OmpR. The authors propose that glycolysis provides a new layer of regulation to the maltose system on the basis that addition of glycolytic carbon sources promotes viability of the mutant. The second paper “The effect of sub-MIC β-lactam antibiotic exposure of Pseudomonas aeruginosa strains from people with cystic fibrosis in a desiccation survival model” examines resistance of Pseudomonas aeruginosa strains to desiccation, which is an important environmental factor to the loss of viability of cells. Strains with a mucoid phenotype exhibit significantly improved desiccation survival when compared with nonmucoid ones, but effects of preincubation with sub-MIC beta-lactam antibiotics on desiccation resistance appear to be agent specific. The third paper “Detection of bacterial endospores in soil by terbium fluorescence” of this special issue addresses the relationship of soil parameters (carbon-to-nitrogen ratio) on the occurrence of bacterial spores and distribution of spores in relation to sampling depth. The results demonstrate that the combination of microwave treatment of soil samples and measurement of terbium dipicolinate (DPA) photoluminescence is a rapid and reliable method for the assessment of bacterial spores. The fourth paper “The sulfate-rich and extreme saline sediment of the ephemeral Tirez lagoon: a biotope for acetoclastic sulfate-reducing bacteria and hydrogenotrophic methanogenic archaea” is on the composition of methanogenic archaea, sulfate-reducing and sulfur-oxidizing prokaryotes in the extreme athalassohaline and particularly sulfate-rich sediment of Tirez Lagoon. The occurrence of hydrogenotrophic methanogenic and acetotrophic sulfate-reducing organisms and winter-summer community structures in Tirez sediment are analyzed by using the PCR-DGGE fingerprint technique for the functional adenosine-5′-phosphosulfate (aprA) and the methyl coenzyme M reductase (mcrA) gene markers. The last paper “Stress responses of Shewanella” of this special issue focuses on stress responses of Shewanella, a group of facultative anaerobes capable of respiring on an array of compounds. As important and potential microorganisms for bioremediation, stress responses of Shewanella have been subjected to an array of analyses, especially with high-throughput technologies such as whole-genome microarrays. This comprehensive review highlights the current understanding of mechanisms by which Shewanella survive and thrive within varied environments, as well as points out promising future research directions. Haichun Gao Tao Weitao Qiang He

Fluorescence enhancement in rare earth doped sol-gel glass by [formula omitted] dimethylformamide as a drying control chemical additive

Studies of terbium fluorescence intensity as a function of annealing temperature reveal the cause of increased fluorescence yields observed in rare earth doped sol-gel silicates prepared using N,N-dimethylformamide (DMF) as a drying control chemical additive (DCCA). While gels prepared with DMF actually have lower fluorescence yields than gels prepared without DMF at lower annealing temperatures, DMF gels can be annealed at much higher temperatures while retaining high optical quality. At these higher temperatures, terbium fluorescence yields increase dramatically as the sol-gel network undergoes densification, closing the pores of the network and eliminating the fluorescence quenching silanols on pore surfaces. DMF is therefore found to enhance the fluorescence properties of rare earth sol-gel glasses by reducing micro-fracturing and facilitating network densification. Further investigations are underway to determine the effectiveness of other promising DCCAs, such as glycerol, and to explore the possibility of exploiting the solubility properties of DCCAs to improve rare earth dopant dispersion.

Detection of Bacterial Endospores in Soil by Terbium Fluorescence

Spore formation is a survival mechanism of microorganisms when facing unfavorable environmental conditions resulting in “dormant” states. We investigated the occurrence of bacterial endospores in soils from various locations including grasslands (pasture, meadow), allotment gardens, and forests, as well as fluvial sediments. Bacterial spores are characterized by their high content of dipicolinic acid (DPA). In the presence of terbium, DPA forms a complex showing a distinctive photoluminescence spectrum. DPA was released from soil by microwaving or autoclaving. The addition of aluminium chloride reduced signal quenching by interfering compounds such as phosphate. The highest spore content (up to 109 spores per gram of dry soil) was found in grassland soils. Spore content is related to soil type, to soil depth, and to soil carbon-to-nitrogen ratio. Our study might provide a basis for the detection of “hot spots” of bacterial spores in soil.

Simultaneous detection of Human Immunodeficiency Virus 1 and Hepatitis B virus infections using a dual-label time-resolved fluorometric assay

A highly specific and novel dual-label time-resolved immunofluorometric assay was developed exploiting the unique emission wavelengths of the intrinsically fluorescent terbium (Tb3+) and europium (Eu3+) tracers for the simultaneous detection of human immunodeficiency virus 1 (HIV-1) and hepatitis B virus (HBV) infections, respectively. HIV-1 infection was detected using a double antigen sandwich format wherein anti-HIV-1 antibodies were captured using an in vivo biotinylated version of a chimeric HIV-1 antigen and revealed using the same antigen labeled with Tb3+ chelate. Hepatitis B surface antigen (HBsAg), which served as the marker of HBV infection, was detected in a double antibody sandwich using two monoclonal antibodies (mAbs), one chemically biotinylated to capture, and the other labeled with Eu3+ nanoparticles, to reveal. The performance of the assay was evaluated using a collection (n = 60) of in-house and commercially available human sera panels. This evaluation showed the dual-label assay to possess high degrees of specificity and sensitivity, comparable to those of commercially available, single analyte-specific kits for the detection of HBsAg antigen and anti-HIV antibodies. This work demonstrates the feasibility of developing a potentially time- and resource-saving multiplex assay for screening serum samples for multiple infections in a blood bank setting.

A selective fluorescence probe for mercury ion based on the fluorescence quenching of terbium(III)-doped cadmium sulfide composite nanoparticles

A fluorescent probe for mercury(II) ions, based on the quenching of fluorescence of terbium(III) ions doped in CdS nanoparticles, has been developed. The terbium(III)-doped cadmium sulfide composite nanoparticles were successfully synthesized through a straightforward one-pot process, with the biomolecule glutathione (GSH) as a capping ligand. In addition, the terbium(III) ions were observed an enhancement of emission intensity, owing to fluorescence energy transfer from the excited CdS particles to the emitting terbium(III). Because of a specific interaction, the fluorescence intensity of terbium(III)-doped CdS particles is obviously reduced in the presence of mercury(II) ions. The fluorescence quenching phenomenon of terbium(III) can be attributed to the fact that the energy transfer system was destroyed by combining with mercury(II). Under the optimal conditions, the fluorescent intensity of terbium(III) ions at 491 nm decreased linearly with the concentration of mercury(II) ions ranging from 4.5 nmol L −1 to 550 nmol L −1. The limit of detection for mercury(II) was 0.1 nmol L −1. This method is simple, practical, relatively free of interference from coexisting substances and can be successfully applied to the determination of mercury(II) ions in real water samples. In addition, the probable mechanism of reaction between terbium(III)-doped CdS composite nanoparticles and mercury(II) was also discussed.

A study on silver nanoparticles-sensitized fluorescence and second-order scattering of the complexes of Tb(III) with ciprofloxacin and its applications

Fluorescence of terbium(III) is sensitized when excited in the presence of ciprofloxacin (CPLX) in the aqueous solution because a Tb(III)–CPLX complex is formed and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb(III)–CPLX complexes with the excitation wavelength of 272 nm. The intensity at 545 nm obviously increases when the silver nanoparticles are added to the Tb(III)–CPLX system, and the relative intensity is proportional to the concentration of CPLX. Based on this phenomenon, a new method for the determination of CPLX has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The intensity is enhanced most by silver nanoparticles at pH 6.0. The calibration graph for CPLX is linear in the range of 3.0 × 10 −9 to 1.0 × 10 −5 mol l −1. The detection limit is 8.5 × 10 −10 mol l −1. The method was applied satisfactorily to the determination of CPLX in tablets and capsules. The results show that silver nanoparticles with certain size and concentration can enhance the fluorescence and SOS intensity of the system.

Sensitive determination of enoxacin by its enhancement effect on the fluorescence of terbium(III)–sodium dodecylbenzene sulfonate and its luminescence mechanism

The fluorescence system of enoxacin–Tb 3+–sodium dodecylbenzene sulfonate (SDBS) was investigated in this paper. The experiments indicated that the fluorescence intensity of Tb 3+–SDBS was greatly enhanced by enoxacin. Accordingly, a sensitive fluorimetric method for determining enoxacin was established. The fluorescence intensity was measured by a 1-cm quartz cell with an excitation wavelength of 290 nm and an emission wavelength of 545 nm. The enhanced fluorescence intensity of the system (Δ F) showed a good linear relationship with the concentration of enoxacin in the range of 5.0×10 −9 to 2.0×10 −6 mol L −1, its correlation coefficient was 0.9992 and the detection limit (S/N=3) was 2.8×10 −9 mol L −1. The presented method was used to determine enoxacin in real pharmaceutical samples. The luminescence mechanism was also discussed in detail. In the fluorescence system of enoxacin–Tb 3+–SDBS, SDBS not only acted as the surfactant but also acted as the energy donor.

Tryptophan and tyrosine to terbium fluorescence resonance energy transfer as a method to “map” aromatic residues and monitor docking

Fluorescent lanthanide ions, with large Stokes shifts and narrow emission bands, are excellent tools for the development of FRET-based assays. In this work, a terbium ion is tethered to a peptide which binds to the BIR3 domain of XIAP, an anti-apoptotic protein. Excitation of tryptophan and tyrosine residues in the BIR3 domain causes the peptide bound terbium ion to fluoresce relative to its distance from these aromatic residues. By developing ligands with terbium ions tethered at different residues, the relative terbium emission can be used to “map” the aromatic residues within the ligand binding pocket.

Fluorescence enhancement and cofluorescence in complexes of terbium(III) with trimellitic acid

The fluorescence of terbium (III) was enhanced by about three orders of magnitude in the presence of trimellitic acid (benzene-1, 2, 4-tricarboxylic acid (TLA)) in aqueous solution at pH 6. The fluorescence intensity could be greatly increased when the system of Tb 3+-TLA was treated with La 3+(or Gd 3+) and TritonX-100. The addition of La 3+(or Gd 3+) enhances the fluorescence of the system by about two orders of magnitude due to cofluorescence, and the TritonX-100 micellar medium plays an important role for stabilization of the system. Both the intermolecular energy transfer mode and intramolecular energy transfer mode are responsible for the mechanism of fluorescence enhancement. In the optimum conditions, the fluorescence intensity is a linear function of Tb 3+ concentration in the range of 7.8 × 10 −9-3.6 × 10 −6 mol/L for the system Tb 3+-La 3+-TLA and 1.0 × 10 −8-4.7 × 10 −6 mol/L for the system Tb 3+-Gd 3+-TLA, and the limits of detection are 4.6 × 10 −10 mol/L and 6.0 × 10 −10 mol/L, respectively.

Fluorometric determination of proteins using the terbium (III)-2-thenoyltrifluoroacetone-sodium dodecyl benzene sulfonate-protein system

It is found that in hexamethylene tetramine (HMTA)–HCl buffer of pH=8.00, proteins can enhance the fluorescence of terbium (III) (Tb 3+)-2-thenoyltrifluoroacetone (TTA)-sodium dodecyl benzene sulfonate (SDBS) system. Based on this, a sensitive method for the determination of proteins is proposed. The experiments indicate that under the optimum conditions, the enhanced fluorescence intensity is in proportion to the concentration of proteins in the range of 4.0×10 −9–7.5×10 −6 g/mL for bovine serum albumin (BSA), 5.0×10 −9–1.5×10 −5 g/mL for human serum albumin (HSA), 1.0×10 −8–7.5×10 −6 g/mL for egg albumin (EA). Their detection limits ( S / N = 3 ) are 0.5, 0.8 and 2.0 ng/mL, respectively. The interaction mechanism is also studied.

Synthesis, Characterization and Fluorescence of Terbium (III) Complexes with Phenylglyoxylic Acid and 2,2-Dipyridine, 1, 10-Phenanthroline, Triphenyl Phosphine Oxide

Three new complexes TbL 3dipy(H 2O) 2, TbL 3phen(H 2O) 2 and TbL 2(TPPO) 2NO 3 were synthesized (L = phenylglyoxylate ion, dipy = 2, 2-dipyridine, phen = 1, 10-phenanthroline, TPPO = Triphenyl phosphine oxide). Elemental analysis, conductivity, IR spectra, and 1HNMR spectra studies were performed. IR spectra indicate that the carboxylate ion of phenylglyoxylate is coordinated to the Tb (III) ion as an unidentate ligand. In 1HNMR, the signals of different hydrogens in phenylglyoxylate ion shift upfield. The excitation and emission spectra of the three solid complexes were recorded at room temperature, in which the optimum excitation wavelengths are 361.0, 359.0 and 367.0 nm for these three complexes, respectively. Four emission bands due to the 5D 4– 7F j(j = 6, 5, 4, 3) transitions were observed for TbL 3dipy(H 2O) 2(489.0, 545.0, 584.0, 620.0 nm) and TbL 3phen(H 2O) 2(490.0, 544.0, 583.0, 620.0 nm). Under the same conditions, only one emission band due to the 5D 4– 7F 5 transition was observed for the complex TbL 2(TP-PO) 2NO 3. The emission intensity of TbL 3dipy(H 2O) 2 is the strongest among the three complexes.

Preparation, Characterization and Application of Fluorescent Terbium Complex-Doped Zirconia Nanoparticles

Novel zirconia-based fluorescent terbium nanoparticles have been prepared as a fluorescent nanoprobe for time-resolved fluorescence bioassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion consisting of a strongly fluorescent Tb(3+) complex, N,N,N(1), N(1)-[2,6-bis(3'-aminomethyl-1'-pyrazolyl)-phenylpyridine]tetrakis(acetate)-Tb(3+)(BPTA-Tb(3+)), Triton X-100, hexanol, and cyclohexane by controlling co-condensation of Zr(OCH(2)CH(3))(4) and ZrOCl(2.) The characterizations by transmission electron microscopy and fluorometric methods indicate that the nanoparticles are uniform in size, 33+/- 4 nm in diameter, and have a fluorescence quantum yield of 8.9% and a long fluorescence lifetime of 2.0 ms. The zirconia-based fluorescent terbium nanoparticles show high stability against basic dissolution in a high pH aqueous buffer compared to the silica-based nanoparticles. A surface modification and bio-conjugation method for the fluorescent nanoparticles was developed, and the nanoparticle-conjugated streptavidin (SA) was used for time-resolved floro-immunoassy (TR-FIA) of human prostate specific antigen (PSA). The result shows that the zirconia-based fluorescent terbium nanoparticles are useful as a fluorescent nanoprobe for time-resolved fluorescence bioassay.

Characterisation of tyrosine-phosphorylation-defective calmodulin mutants

Using site-directed mutagenesis, we have produced three calmodulin (CaM) mutants in which one or the two tyrosine residues of native CaM were substituted by phenylalanine. The three variants, denoted CaM(Y99F), CaM(Y138F), and CaM(Y99F/Y138F), were highly expressed in transformed Escherichia coli BL21(DE3)pLysS and purified in high yield. The three CaM mutants were able to activate the cyclic nucleotide phosphodiesterase and the plasma membrane Ca 2+-ATPase, and present the characteristic Ca 2+-induced electrophoretic mobility shift of native CaM. CaM(Y138F) and CaM(Y99F/Y138F), however, showed a slightly higher electrophoretic mobility than CaM(Y99F) or wild type CaM. The molar extinction coefficient of native CaM at 276 nm decreases 50% in CaM(Y99F) and CaM(Y138F), while the 276 nm peak disappears in CaM(Y99F/Y138F). Terbium fluorescence studies with the different CaM mutants indicate that Y99 (but not Y138) closely interacts with Ca 2+ in the III Ca 2+-binding domain. The epidermal growth factor receptor (EGFR) and the non-receptor tyrosine kinase c-Src phosphorylate CaM(Y99F) and CaM(Y138F) at a lesser extent than wild type CaM, while they fail to phosphorylate CaM(Y99F/Y138F) as expected. All resulting phospho-(Y)CaM species present the characteristic Ca 2+-induced electrophoretic mobility shift observed in non-phosphorylated CaM. Quantitative analysis of the different phospho-(Y)CaM species suggests that the relative phosphorylation of Y99 and Y138 in wild type CaM by both the EGFR and c-Src is different than the respective phosphorylation of either Y99 in CaM(Y138F) or Y138 in CaM(Y99F).

Improved Antenna Effect of Terbium(III)-Cored Dendrimer Complex and Green-Luminescent Hydrogel by Radical Copolymerization

This study explored practical applications of the unique green fluorescence of terbium(III)-cored poly(benzyl ether) dendrimer complexes for luminescence polymeric materials. At first, to maximize the fluorescence ability, we examined the influence of the isomerism in the dendron skeleton, both at the focal point and the hyperbranch repeating unit. Next, a 4-vinylphenyl group was successfully introduced at the terminal of the dendron subunit for radical polymerization. A 3,4-dioxybenzoate moiety for the focal point of the dendron gave stronger fluorescence than the usual 3,5-isomer; however, the authentic 3,5-dioxybenzyl ether moiety appeared the best hyperbranch repeating unit for the fluorescence ability. The terminal vinyl groups enabled the copolymerization of the terbium(III)-cored dendrimer complex with N-isopropylacrylamide, resulting in a green-fluorescent, clear hydrogel. The hydrogel showed a gel phase transition at 33-35 °C to exhibit temperature-induced switching in the opacity.

Metal binding to cowpea chlorotic mottle virus using terbium(III) fluorescence.

Metals are thought to play a role in the structure of many viruses. The crystal structure of the T=3 icosahedral cowpea chlorotic mottle virus (CCMV) suggests the presence of 180 unique metal-binding sites in the assembled protein cage. Each of these sites is thought to involve the coordination of the metal by five amino acids contributed from two adjacent coat protein subunits. We have used fluorescence resonance energy transfer (FRET), from tryptophan residues proximal to the putative metal-binding sites, to probe Tb(III) binding to the virus. Binding of Tb(III) was investigated on the wild-type virus and a mutant where the RNA binding ability of the virus was removed. Tb(III) binding was observed both in the wild-type virus ( K(d)=19 microM) and the mutant ( K(d)=17 microM), as monitored by the increase in Tb(III) fluorescence (545 nm) and concomitant decrease in tryptophan fluorescence (342 nm). Competitive binding experiments showed Ca(II) to have about 100-fold less affinity for the binding sites ( K(d)=1.97 mM). This is the first direct evidence of metal binding to the putative metal-binding sites, originally suggested from the crystal structure of CCMV.