The study of terbium regenerated bacterirhodopsin

Bacteriorhodopsin (bR) is the only retinal-contain- ing protein in the purple membrane of Halobacterium halobium[1]. Upon illumination, the protein undergoes a photocycle and pumps protons across the cell mem-brane[2,3]. It has been found that well-washed…     

Biohybrid based on layered terbium hydroxide and applications as drug carrier and biological fluorescence probe

Aspirin (abbr. ASA) is intercalated into the layered terbium hydroxide (LTbH) by anion exchange method. Structure, chemical compositions, thermostability, morphology, luminescence property, cytotoxic effects and controlled‐release behaviors have been investigated. The ASA molecules may embed between layers with monolayered vertical arrangement, and the thermal stability of organics was enhanced after intercalation. The Tb³⁺ luminescence in ASA‐LTbH composites was enhanced compared with LTbH precusor and the luminescence intensity increased with the deprotonation degree. The cytotoxic effect of LTbH was observed with a sulforhodamine B (SRB) colorimetric assay, which revealed that the LTbH showed low cytotoxic effects. In addition, the ASA‐LTbH composites exhibited a sustained release of ASA in Na₂HPO₄‐NaH₂PO₄ buffer solution at pH 6.86 and 37°C. Construction of LRHs composites with drug molecules provided a beneficial pathway for preparing biohybrid based on LRHs, which may have potential applications in drug delivery carrier and biological fluorescence probe.     

Study of terbium(III)–dextran and terbium(III)–α-methyl glucoside interactions

The interaction of dextran with terbium(III) was studied in aqueous solution, pH 3.0–6.6, by fluorescence and optical rotatory dispersion. The polysaccharide enhances Tb(III) fluorescence intensity when the system is excited at the 290-nm hypersensitive transition (⁷F₆ → ⁵H₄). The dextran rotatory power is decreased in the presence of the metal ion. The results indicate that a 38% maximum of the polymer repeat units are coordinated. Complex formation occurs with displacement of water from the cation coordination sphere by hydroxyl groups at the second and third carbon atoms of the pyranoside ring. As the pH increases, a more asymmetric complex is formed. The α-methyl glucoside, low molecular weight dextran analogue, interacts with Tb(III) less strongly than dextran. Fluorimetric titrations indicated that the order of binding ability to polysaccharide is Tb(III) > Al(III) > Ca (II). © 1993 John Wiley & Sons, Inc.     

Fluorescence lifetime of terbium(III) as a probe for the ion-binding properties of tactic poly(methacrylic acids)

The binding properties of trivalent metal ions to polyelectrolytes were investigated through the use of terbium [Tb(III)] in fluorescence studies. The fluorescence intensity and lifetimes of the lanthanide ions are directly dependent upon the number of water molecules bound to their inner coordination sphere. The more efficiently a ligand coordinates to a lanthanide ion, the more water molecules are expelled and consequently, the greater the fluorescence intensity and lifetime. This effect was used to probe for differences in the complexation behavior of tactic polymers. Aqueous solutions of isotactic and syndiotactic poly(methacrylic acid) (PMA) were neutralized and complexed with Tb(III) ions. The fluorescence intensity of the 286 nm hypersensitive excitation band was monitored and the lifetimes were measured using several excitation wavelengths. It was found that the isotactic PMA/Tb(III) complex exhibited a six times greater fluorescence intensity than the syndiotactic PMA complex. Lifetime measurements gave the number of water molecules coordinated by Tb(III) in the isotactic complex to be 2.4 while 3.4 waters remained bound to the Tb(III) ion in the syndiotactic PMA complex. These results indicate that isotactic PMA has the greater binding affinity towards Tb(III) ions. © 1997 John Wiley & Sons, Inc.     

The Synthesis of Novel Crown Ethers. Part IV. Coumarin Derivatives of [18]crown-6 and Cation Binding from Fluorescence Spectra

4-H, 4-methyl and 4-phenyl-1-benzopyran-2-one derivatives of [18]crown-6 derivatives were synthesised from 6,7- and 7,8-dihydroxy-1-benzopyran-2-one reacting with pentaethylene glycol ditosylate in K₂CO₃/DMF/water. The products were identified by elemental analysis, EI-GC-mass spectra and ₁H-NMR spectroscopy. The Na⁺ association constants of some coumarin derivatives were determined with an ion selective electrode in water. The Na⁺ , K⁺, Ba²⁺ and Sr²⁺ binding role of such compounds were particularly observed as remarkable alterations in acetonitrile. The 1 : 1 associations constants of K⁺ and Na⁺ with some coumarin-[18]crown-6 derivatives estimated by this way in acetonitrile exhibited the utility of complexing enhanced quenching fluorescence spectra for the ion binding power of the such macrocycles.     

The synthesis of novel 4-(3,4-dimethoxyphenyl)chromenone-crown ethers and their cation binding,as determined using fluorescence spectra

o-Dihydroxy-4-(3,4-dimethoxyphenyl)-chromenones (coumarins; 3a,b) were synthesised from 1,2,3-trihydroxy- or 1,2,4-triacetoxybenzenes through a reaction with ethyl 3-(3,4-dimethoxyphenyl)-3-oxopropanoate in H₂SO₄ or CF₃COOH. The chromenone-crown ethers (4a–f) were prepared from the cyclic condensation of o-dihydroxy-4-(3,4-dimethoxyphenyl)chromenones (3a,b) with poly(ethylene glycol) ditosylates, in the presence of CH₃CN/alkali carbonates. The chromatographically purified original chromenone-crown ethers were identified by ¹H NMR, ¹³C NMR, MALDI-TOF mass spectrometry and elemental analysis. The 1:1 binding constants of Li⁺, Na⁺ and K⁺ with the chromenone-crown ethers were estimated in acetonitrile using fluorescence emission spectroscopy. The complexing-enhanced fluorescence spectra and complexing-enhanced quenching fluorescence spectra, along with the cationic recognition rules of the crown ethers allowed the ion binding powers to be determined.     

Development of functionalized terbium fluorescent nanoparticles for antibody labeling and time-resolved fluoroimmunoassay application

Silica-based functionalized terbium fluorescent nanoparticles were prepared, characterized and developed as a fluorescence probe for antibody labeling and time-resolved fluoroimmunoassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion containing a strongly fluorescent Tb³⁺ chelate, N,N,N¹,N¹-[2,6-bis(3′-aminomethyl-1′-pyrazolyl)phenylpyridine] tetrakis(acetate)-Tb³⁺ (BPTA-Tb³⁺), Triton X-100, octanol, and cyclohexane by controlling copolymerization of tetraethyl orthosilicate (TEOS) and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AEPS) with ammonia water. The characterizations by transmission electron microscopy and fluorometric methods show that the nanoparticles are spherical and uniform in size, 45 ± 3 nm in diameter, strongly fluorescent with fluorescence quantum yield of 10% and a long fluorescence lifetime of 2.0 ms. The amino groups directly introduced to the nanoparticle’s surface by using AEPS in the preparation made the surface modification and bioconjugation of the nanoparticles easier. The nanoparticle-labeled anti-human α-fetoprotein antibody was prepared and used for time-resolved fluoroimmunoassay of α-fetoprotein (AFP) in human serum samples. The assay response is linear from 0.10 ng ml⁻¹ to about 100 ng ml⁻¹ with the detection limit of 0.10 ng ml⁻¹. The coefficient variations (CVs) of the method are less than 9.0%, and the recoveries are in the range of 84-98% for human serum sample measurements.     

A CIDEP and fluorescence study of the oxidation of vitamin E: The vitamin E radical cation

The photochemical and thermal oxidations of vitamin E in trifluoroacetic acid were investigated by the combination of electron spin resonance, chemically induced dynamic electron polarization, and fluorescence techniques. Two independent thermal pathways led to the formation of the vitamin E radical cation in which one of the paths involved the intermediate neutral semiquinone radical. Photo-oxidation, however, did not involve the neutral radicals. The fluorescence spectra of both the neutral and the charged forms of the vitamin E radicals are reported here for the first time. Some model charge transfer reactions involving the vitamin E radical cation were reported.     

Dynamic chemical devices: modulation of photophysical properties by reversible, ion-triggered, and proton-fuelled nanomechanical shape-flipping molecular motions

The terpy-derived (terpy=terpyridine) ligand 1 has an extended W shape in which the two appended photoactive pyrenyl groups are held apart. On binding of a zinc(II) ion with a terpy group, ligand 1 is converted into complex 2 whereby it adopts a U shape, thus stacking the aromatic units. This structural modification leads to a very pronounced change in photophysical properties: from a highly fluorescent free ligand to a very weakly emitting complex. The W/U structural switching can be reversibly induced by the addition of a competitive tren ligand, which binds and releases a zinc(II) ion under protonation/deprotonation cycles, thus leading to oscillations in light emission. Therefore, the present system performs periodic modulation of optical output through a nanomechanical shape-flipping motion, triggered by metal ion binding and fuelled by acid-base neutralisation energy. Overall, it represents an ion-triggered opto-mechanical supramolecular device.     

A study of vitamin A radical cation generated by chemical and radiolytic oxidation

Electron transfer reaction between vitamin A (1) and tris(p-bromophenyl)aminium hexachloroautimonate (2) in dichloromethane (DCM) has been investigated by means of UV-VIS absorption and ESR spectroscopy. The title radical cation formed in the reaction was characterized by a new absorption band around 600 nm and a singlet unresolved ESR spectrum with g factor of 2.0038-2.0039 and line width of 20 G. Further studies indicated that ESR pattern and parameters of the radical cation generated by 7-irradiation of 1 in CFCl3 matrix at 77 K are consistent with that resulted in the chemical oxidation in DCM at ambient temperature.     

Vacuum fusion determination of oxygen in gadolinium,terbium metal and iron-terbium alloy

The extraction conditions for the accurate determination of oxygen in gadolinium, terbium and iron-terbium alloy using vacuum fusion analysis were studied. The influence of the gettering effect, the analyzing temperature and the weight ratio of the bath metal to the sample were investigated. Oxygen values of gadolinium and terbium were measured by the graphite crucible, the graphite capsule, the tin bath, the iron-tin bath and the platinum-tin bath techniques in the temperature range of 1500–2100 °C using vacuum fusion analysis. These oxygen values were compared with those obtained by inert gas fusion analysis. In inert gas fusion analysis, the samples were analyzed with iron and tin in a tin capsule, and the samples with platinum in a tin capsule were analyzed in a graphite capsule enclosing with carbon powder. Oxygen values of both metal samples in the graphite capsule at 2000 °C, with an iron-tin bath at 1850 °C and a platinum-tin bath at 2000 °C in vacuum fusion analysis, were respectively in good agreement within their errors; the oxygen values of gadolinium were also in good agreement with that from inert gas fusion analysis in the iron-tin bath, but those of terbium were not in agreement. This agreement for gadolinium guarantees the reliability of the conditions for the accurate determination, and the difference of oxygen values for terbium suggests a need for further consideration on the conditions of the inert gas fusion analysis.     

Stoichiometry and morphology in terbium nitrate-poly(ethylene oxide) macromolecular complex

The Tb (NO₃)₃-PEO system was characterized to have a solubility limit equivalent to n ? 6.5 and a coordination number of 12.4 ± 0.1, compared to 5.0 and 10.9 ± 0.1 for the Nd(NO₃)₃-PEO system. The greater coordination involving Tb³⁺ appears to be responsible for the lower asymptotic glass transition temperature at high doping levels of the Tb(NO₃)₃-PEO complex. In both systems, anhydrous amorphous complexes were obtained below the respective solubility limits, over which apparent solubilities were found to be enhanced by the presence of tightly bound moisture while retaining the amorphous character of the complexes. Whereas partial precipitation was observed in the Tb(NO₃)₃-PEO system upon exposure to ambient moisture, both complexation and amorphous character were found to persist in the Nd(NO₃)₃-PEO system in the presence of absorbed moisture. © 1994 John Wiley & Sons, Inc.     

含铽配合物的合成及其荧光性研究

采用稀土铽金属醇盐与丙烯酸、乙酰丙酮、中性配体(邻菲啰啉或联吡啶）反应，在非水介质下合成具有高聚合活性的含铽配合物单体，通过元素分析、红外光谱、紫外光谱确定了它们的组成和结构，合成的铽配合物单体溶于一般的有机溶剂并能强烈吸收紫外光谌芤杭胺勰┳刺卵芯空庑┑ヌ宓挠庑浴T谧罴鸭し⒉ǔは拢蔷芊⑸滹胱拥奶卣饔猓ド越虾谩Q返淖刺叭芗恋募远耘浜衔锏牡ヌ宓挠庑杂薪洗笥跋欤行耘涮辶诜茊⒘拎さ囊芴岣咚堑挠夥⑸淝慷取     

Crystal structure and luminescence property of ternary terbium p-aminobenzoic acid complexes with different second ligands

Ternary terbium complexes with p-aminobenzoic acid (HL), [TbL₃(DMSO)(H₂O)]₂ (1), [TbL₃(DMF)(H₂O)]₂ (2) and [TbL₃(Bpy)(H₂O)]₂·2H₂O (3) (DMSO=dimethyl sulfoxide, DMF=N, N- dimethylformamide, Bpy=2, 2′- bipyridyl) have been synthesized, and their crystal structures determined. The luminescence properties of these complexes, including both the emission quantum yield and the fluorescence lifetime, have been investigated. The effect of a second ligand on the crystal structure and luminescence property of the ternary terbium p-aminobenzoic acid complexes, and the relationship between luminescence properties and crystal structure, including coordination mode of the L⁻ ligand and the characteristics of a second ligand, are discussed.     

铽-环丙沙星稀土敏化荧光猝灭法测定叶酸

在pH=5.0的醋酸-醋酸钠缓冲溶液中,铽(与环丙沙星反应形成1∶2的稳定络合物,其最佳激发、发射波长分别为λex=330nm、λem=545nm。在该反应体系中加入适量叶酸溶液,铽(与环丙沙星络合物的激发、发射波长位置不变,但荧光强度下降。利用这一现象,建立了简单、快速、灵敏的测定叶酸的荧光分析方法。该方法保持了叶酸结构的完整性,叶酸浓度在22~880μg/L范围内符合线性关系;方法检出限为7.8μg/L。用于片剂及胶囊中叶酸含量的测定,结果满意。6次平行测定该方法回收率为93.7%~107.9%,相对标准偏差为0.38%~2.8%。     

Time-resolved luminescence of terbium complexes with poly(2- and 4-vinylpyridine N-oxide)s in aqueous solution

Terbium complexes with polymer ligands of poly(2- and 4-vinylpyridine N-oxide)s (P2VPNO, P4VPNO) in aqueous solution were prepared and characterized. Multi-exponential decays of the ⁵D₄ → ⁷F₅ terbium transition at 545 nm of [P2VPNO-Tb³⁺] and [P4VPNO-Tb³⁺] complexes were measured. The non-linearity of semi-logarithmic plots of time-resolved luminescence was more pronounced in [P4VPNO-Tb³⁺] than in [P2VPNO-Tb³⁺], being reduced by addition of salts such as sodium formate or acetate. We assume that multi-exponential decays of Tb³⁺ in the complexes are caused by a back metal-to-ligand energy transfer via triplet state of N-oxide polymer ligand. By carrying out separate experiments in water and deuterium oxide, the number of coordinated water molecules in the [P4VPNO-Tb³⁺] complex was estimated as 4-5, assuming that the Tb³⁺ aqua complex contains nine water molecules.     

The cation binding of benzo crown ethers in acetonitrile using fluorescence spectroscopy

The effects of Na⁺, K⁺ and Li⁺ cations on the fluorescence spectra of benzo[15]crown-5, benzo[18]crown-6 and dibenzo[18]crown-6 were investigated in acetonitrile. The alkali cation role observed was usually the complexation-enhanced quenching fluorescence effect (CEQF) in acetonitrile due to the increased fluorescence quenching rate of the complexed fluoroionophore. The association constants for 1 :1 stoichiometry InK _a have been obtained using the relationship 1/K _a[L ₀] = (1 –P)²/P. It was shown that the preferential interaction rule of compatibility of cationic radii and macrocyclic ring size is in excellent agreement with the association constants obtained by fluorescence spectroscopy. The order of InK _a found for benzo[15]crown-5 complexation was Li⁺ > Na⁺ > K⁺ and K⁺ > Na⁺ > Li⁺ for benzo[18]crown-6 in acetonitrile.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Intercalation assembly of optical hybrid materials based on layered terbium hydroxide hosts and organic sensitizer anions guests

Optical hybrid materials based on inorganic hosts and organic sensitizer guests hold promise for a virtually unlimited number of applications.In particular,the interaction and the combination of the properties of a defined inorganic matrix and a specific sensitizer could lead to synergistic effects in luminescence enhancing and tuning.The current article focuses on the intercalation assembly of optical hybrid materials based on the layered terbium hydroxide(LTbH) hosts and organic divalent carboxylic sensitizer anion guests by a hydrothermal process.The studies on the interactions between hosts and guests indicate that the type and arrangement of organic guests in the layer spacing of the LTbH hosts can make a difference in the luminescence of the hybrid inorganic-organic materials.