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PubMed1978

Measurement of binding of terbium to DNA.

This communication demonstrates further that terbium(III) can be used as a probe for DNA. The stoichiometry of terbium binding to DNA was measured by two new methods. In the first method, calf-thymus DNA was titrated with radioactive terbium-160, which is an isotope of the common terbium-159. The resulting DNA-terbium complex was trapped and measured on millipore filters. In the second method, a peak of UV absorption of terbium was found at 219 nm and was used to measure stocichiometry. By both methods, the stoichiometry of binding was one Tb(III) for each three available phosphate groups in DNA. Finally, a rapid method was developed using terbrium-160 to measure the amount of nucleic acid in a solution.

Animals↗

PubMed1975

Terbium binding to ribosomes and ribosomal RNA.

Terbium binding to rat liver ribosomes and ribosomal RNA (rRNA) was examined by equilibrium dialysis and fluorescence spectroscopy. Upon binding to ribosomes and rRNA, the enhancement of terbium fluorescence emission at both 488 and 541 nm was dependent only upon the amount of bound terbium and independent of ionic strength. Binding profiles for ribosomes and rRNA suggested that terbium was bound to ribosomes primarily through rRNA interactions. Data suggested that terbium mimicked characteristics previously described for interactions between ribosomes and magnesium. It is proposed, therefore, that fluorescence of terbium bound to ribosomes may prove useful in studies on the nature and extent of interactions between ribosomes and magnesium.

Animals↗

PubMed2001

[Uncommon fluorescent properties of nano-structured terbium (III)-phthalic acid complex in polyvinylpyrrolidone].

Nano-sized terbium(III)-phthalic acid complex was prepared in polyvinylpyrrolidone. It's fluorescent spectrum has been investigated, compared to that of common terbium(III)-phthalic acid complex and terbium(III)-polyvinylpyrrolidone complex. The results show that fluorescent characterizations of Nano-sized terbium(III)-phthalic acid complex is obviously different from that of common terbium(III)-phthalic acid complex and terbium(III)-polyvinylpyrrolidone. The relative intensity and half-height width of main emission peaks are obviously varied, two splitting peaks are displayed.

Chelating Agents↗

PubMed1977

Energy transfer between terbium and iron bound to transferrin: reinvestigation of the distance between metal-binding sites.

The addition of trivalent iron, gallium, and terbium ions to the metal binding sites of human transferrin has been investigated by fluorescence and spectrophotometric measurements. Results are consistent with the possibility that the addition of ferric nitrilotriacetate to apotransferrin does not lead to a random distribution of iron bound to the two metal-binding sites on the protein, but rather an asymmetric distribution with iron bound mainly to one of the sites. The subsequent addition of terbium leads to the binding of terbium ions to the vacant sites on monoferric transferrin molecules, and observations of the intensity of terbium fluorescence from such samples provides clear evidence of transfer of excitation energy from the terbium site to the iron site. These results lead to the estimate that the two metal-binding sites of human transferrin are separated by a distance of 25 +/- 2 A, in disagreement with an earlier report (Luk, C. K. (1971), Biochemistry 10, 2838) that the sites were separated by more than 43 A. Consideration of the dimensions of transferrin indicates that the two sites lie relatively close to each other on the macromolecule.

Apoproteins↗

PubMed2006

Luminescence dynamics of terbium monodipicolinate in ethyl ammonium nitrate.

Energy level dynamics are experimentally examined for terbium monodipicolinate dissolved in ethyl ammonium nitrate (EAN). The luminescence lifetime, the luminescence risetime, and the absorption spectrum of terbium monodipicolinate in EAN are measured. The risetime of luminescence in terbium dipicolinate is experimentally shown to be nonzero and measurable. A dynamic model is presented that describes the evolution of terbium dipicolinate luminescence in EAN. The long risetime in the model is caused by a resonance between the 5E6 state in the terbium cation and the lowest triplet state (T1) in the dipicolinate anion. Bacterial endospore components dissolved in EAN are used to check the time resolution of the experimental apparatus. EAN is discussed partly because it is a room-temperature ionic liquid (RTIL), which is a class of solvents that may be useful for detecting bacterial endospores in the atmosphere.

Computer Simulation↗

PubMed1991

Luminescence of peptide-bound terbium ions. Determination of binding constants.

Luminescence of Tb3+ ions bound to a calmodulin fragment has been studied. It is shown that during their lifetime excited ions dissociate from the peptide. If concentration of free peptide is high enough they can be coordinated again. As a consequence, observed terbium luminescence lifetime and intensity depends not only on binding equilibrium, but also on concentration of free peptide molecules. In such a system terbium binding constant cannot be correctly determined by simple steady-state measurements of luminescence intensities. Instead, terbium luminescence decay curves measured at various peptide concentrations must be analysed. Such an analysis has been made for a fragment of the IIIrd calcium binding domain of rat testis calmodulin. Rate constant of terbium association and the equilibrium binding constant corresponding to the best fit of theoretical functions to experimental points have been determined.

Amino Acid Sequence↗

PubMed1990

Terbium simulates the action of calcium on electrophysiological activity in the isolated fish retina.

It has been suggested that terbium (Tb) could be substituted for calcium (Ca) in biological tissue and, because of its useful spectroscopic properties, provide an assessment of calcium distribution in the tissue. In order to assess their physiological effects, we have examined the action of free terbium ions on the membrane potential and light-evoked responses of horizontal cells, and on the massed light evoked response (ERG) of the neural retina. Measurements were performed by intracellular and extracellular recording from the isolated fish retina, superfused with Ringers of various ionic compositions, and certain technical difficulties which occurred in the use of terbium are discussed. We show that Tb ions mimic Ca ions in suppression of the ERG and in hyperpolarization of the horizontal cell membrane potential. The effects of Tb persist after its removal from the superfusate for a longer period than do those of calcium, which indicates that terbium binds more firmly at its site(s) activity. Tb and Ca both suppress the light-evoked S-potentials from the horizontal cells, although some differences were observed in the waveform of the S-potentials during the onset of suppression. We conclude that the physiological effects of Tb on the retina are essentially similar to those of Ca, and that Tb could, therefore, prove a useful marker of Ca distribution in neural tissue.

Animals↗

PubMed2006

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.

Binding Sites↗

PubMed2006

Synthesis and novel fluorescence phenomenon of terbium complex with a new Schiff base ligand derived from condensation of triaminotriethylamine and 3-indolemethanal.

A new Schiff base ligand with tripodal structure, N,N',N''-tri-(3-indolemethanal)-triaminotriethylamine (L), and its complex with terbium was synthesized. The complex was characterized by element analysis, IR spectra, mass spectra, thermal analysis and molar conductivity. The terbium ion was found to coordinate to the Schiff base nitrogen atoms and the bridgehead nitrogen atom. The fluorescence properties of the complex in aqueous solutions were studied. Under the excitation of UV light, the complex exhibits characteristic fluorescence of terbium ion. H(+) concentration could strongly enhance the luminescence of terbium complex with L in aqueous solutions. This phenomenon will make the new complex favorable to be used in the fluorescence switches and sensors. The mechanism of the fluorescence enhancement by protonation of the indole nitrogen atoms is due to the suppressed photoinduced electron transfer (PIET) fluorescence quenching when adding acid.

Ethylenediamines↗

PubMed1983

Anomalous x-ray scattering from terbium-labeled parvalbumin in solution.

We have used anomalous small-angle x-ray scattering as a structural probe for solutions of rabbit parvalbumin labeled with terbium. This technique makes use of the large changes in the terbium scattering factor that occur when the x-ray energy is tuned around an L3 absorption edge of this heavy-atom label. These changes in scattering result in changes in the small-angle scattering curve of the labeled protein as a whole, which can then be analyzed to derive structural information concerning the distribution of labels in the protein. Based on a Gaussian model for the protein electron density, the mean distance from the terbiums to the protein center of mass is determined to be 13.2 A and is consistent with crystallographic results. Our results demonstrate the usefulness of terbium as an anomalous scattering label and provide criteria to help establish anomalous scattering as a reliable structural technique for proteins in solution.

Animals↗

PubMed2003

Synthesis and infrared and fluorescence spectral properties of luminescent terbium and europium complexes with open-chain carboxylate crown ethers.

Two open-chain carboxylate crown ether ligands and their terbium(III) and europium(III) complexes were synthesized and characterized. The terbium and europium ions were found to coordinate to the carboxylate oxygens. The fluorescence properties of europium complexes in the solid state and terbium complexes in the solid state and in the organic solvent were studied in detail, respectively. Under the excitation of ultraviolet light, strong green fluorescence of solid terbium complexes and red fluorescence of solid europium complexes were observed. These observations show that the two ligands favor energy transfer to the emitting energy level of Tb(3+). Some factors that influencing the fluorescent intensity were also discussed.

Carboxylic Acids↗

PubMed1981

Distance between metal-binding sites in transferrin: energy transfer from bound terbium (III) to iron (III) or manganese (III).

The distance between the two metal-binding sites of human serum transferrin has been studied by observing energy transfer between an excited terbium ion bound at one site and a ferric (or manganic) ion bound at the other site of the same transferrin molecule. From the observed reduction in terbium lifetime (relative to that of terbium transferrin), it is concluded that the intersite distance is 3.55 +/ 0.45 nm. This distance is reconciled with two conflicting earlier reports that the separation between sites is greater than 4.3 nm [Luk, C.K. (1971) Biochemistry 10,2838-2844] or is equal to 2.5 +/ 0.2 nm [Meares, C.F., & Ledbetter, J.E. (1977) Biochemistry 16, 5178-5180]. The difficulty of accurately measuring the quantum yield of protein-bound terbium provides the principal source of uncertainty in these measurements.

Binding Sites↗

PubMed2004

Time gating improves sensitivity in energy transfer assays with terbium chelate/dark quencher oligonucleotide probes.

Lanthanides are attractive as biolabels because their long luminescence decay rates allow time-gated detection, which separates background scattering and fluorescence from the lanthanide emission. A stable and highly luminescent terbium complex based on a tetraisophthalamide (TIAM) chelate is paired with a polyaromatic-azo dark quencher (referred to as a Black Hole Quencher or BHQ) to prepare a series of 5'TIAM(Tb)/3'BHQ dual-labeled oligonucleotide probes with no secondary structure. Luminescence quenching efficiency within terbium/BHQ probes is very dependent on the terbium-BHQ distance. In an intact probe, the average terbium-BHQ distance is short, and Tb --> BHQ energy transfer is efficient, decreasing both the terbium emission intensity and lifetime. Upon hybridization or nuclease digestion, which spatially separate the Tb and BHQ moieties, the Tb luminescence intensity and lifetime increase. As a result, time-gated detection increases the emission intensity ratio of the unquenched probe/quenched probe due to the shorter lifetime of the quenched species. A 40-mer probe that has a 3-fold increase in steady-state luminescence upon digestion has a 50-fold increase when gated detection is used. This study demonstrates that time gating with lanthanide/dark quencher probes in energy transfer assays is an effective means of improving sensitivity.

Amides↗

PubMed1986

Kinetics of cadmium and terbium dissociation from calmodulin and its tryptic fragments.

The kinetics of cadmium and terbium dissociation from bovine testis calmodulin and its tryptic fragments have been studied by stopped-flow fluorescence methods, using the calcium indicator Quin 2. Studies of the tryptic fragments TR1C and TR2C, comprising the N-terminal or C-terminal half of calmodulin, have clearly identified cadmium binding sites I and II as the low-affinity (rapidly dissociating) sites and sites III and IV as the high-affinity (slowly dissociating) sites. Thus the site preference of cadmium is the same as that of calcium. For terbium, however, sites I and II are the high-affinity sites and sites III and IV are the low-affinity sites. Thus, the site preference or terbium is not the same as that of calcium and cadmium. In contrast to previous studies with calcium, we observe two kinetic processes for dissociation from sites III and IV for experiments with both cadmium and terbium. Possible models for the binding of metal ions are discussed.

Binding Sites↗

PubMed1984

Kinetic effects of terbium ions on muscarinic acetylcholine receptors of murine neuroblastoma cells.

Preincubation of murine neuroblastoma cells (clone N1E-115) with terbium chloride resulted in a significant potentiation of carbachol-mediated increase in cyclic GMP formation. This effect was accompanied by a shift of the peak response from 30 s to 120 s and a 6-fold decrease in carbachol concentration producing half-maximal responses, in addition to a significant increase in the Hill coefficient. Terbium ions also caused a significant decrease in the affinity and an increase in the maximum binding of [3H]quinuclidinyl benzilate to muscarinic receptors, the change in affinity being mainly due to a decrease in the association rate. Preincubation of cells with 1 mM carbachol for 4 h (the desensitized state of the muscarinic receptor) resulted in a decrease in the ability of terbium to alter [3H]quinuclidinyl benzilate binding. The effects of terbium reported here might be due to its affecting muscarinic receptor-effector coupling, which is considered to be lost upon receptor desensitization.

Animals↗

PubMed2001

[Energy transfer between electric polymer PVK and terbium complex and its transmission electronmicroscope (TME) study].

A chloroform-soluble terbium complex, which is confirmed to be Tb(aspirin)3 phen using element analysis and FT-IR spectroscopy, was synthesized. Photoluminescent investigation on the terbium complex and PVK-terbium complex composite was conducted. Förster energy transfer occurred between the terbium complex and the PVK matrix. There are no overlap between UV spectrum of the complex and the emission spectrum of PVK, however, overlap is observed between the excitation spectrum of the complex and the emission spectrum of PVK. Therefore, we suggest that the necessary condition of Förster energy transfer should be overlap between the excitation (not UV) spectrum of one complex and the emission spectrum of polymer matrix. Further investigation indicates that the emission of PVK can be suppressed at different extents by doping various amount of Tb(aspirin)3 phen into PVK films. The ratio of Tb(aspirin)3 phen: PVK = 1:2 (wt%) are regarded as an optimized ratio for limiting the emission of PVK. TEM images of PVK/Tb(aspirin)3 phen films reveal that nanoparticles of the Tb complex are dispersed in the PVK matrix. The size of the aggregated complex in PVK matrix is 20-30 nm. The film is not homogeneous as dark regions co-exist with light region in the TEM images. This phenomenon may be related to the short lifetime of electroluminescent devices.

Chelating Agents↗

PubMed1994

[Hygienic regulation of yttrium, terbium, ytterbium and lutetium fluorides in the air of the workplace].

The study (experiments on animals and on culture of rats' peritoneal macrophages) covered fluorides of rare-earth metals (REM) assigned to yttrium group--yttrium, terbium, ytterbium, lutetium. Fluorides of REM have low toxicity and cumulativity, induce no local irritation of skin and eyes. Fluorides of yttrium, terbium and lutetium, if administered into stomach, result in specific intoxication (fluorosis). Fluoride of ytterbium did not cause such intoxication. According to short-term tests of cytotoxicity, the foreseeable fibrogenic danger for ytterbium fluoride is moderate, for fluorides of yttrium, terbium and lutetium is mild. The authors recommend to control the level of yttrium, terbium and lutetium fluorides in the air of workplace through the MACs for the fluorides at 2.5 mg/cu m (maximal single concentration) and 0.5 mg/cu m (average shift concentration), the level of ytterbium fluoride as moderate fibrogenic dust at 6 mg/cu m.

Air Pollutants, Occupational↗

PubMed2003

Spectrofluorometric determination of trace amounts of terbium with 4-chlorosalicylic acid, EDTA, and cetyltrimethylammonium bromide.

The quadruple complex formed by terbium with 4-chlorosalicylic acid (CSA), EDTA and cetyltrimethylammonium bromide (CTMAB) has been used for the sensitive spectrofluorometric determination of terbium in mixed rare earths. The effect of the experimental conditions on the fluorescence intensity was defined. Under the optimum conditions selected, the fluorescence intensity was linear with the terbium concentration in the range of 3.0 x 10(-8)-1.0 x 10(-5) mol/L with a detection limit of 8.0 x 10(-9) mol/L (S/N = 3). It has been satisfactory for the determination of terbium in mixed rare earths with good recovery.

Journal Article↗