酒石酸脱除单铽转铁蛋白中铽（III）的荧光动力学研究

0.01 mol/L Hepes, pH7.4，室温条件下，以酒石酸为脱除剂，监测铽（III） 与脱铁蛋白结合的两种配合物C端单铽转铁蛋白和N端单铽转铁蛋白随酒石酸浓度变 化的脱除动力学，根据其动力学行为，我们推测存在两种平行的脱除途径：一次途 径和饱和途径，其中C端单铽转铁蛋白的铽（III）脱除呈现饱和与一次相结合途径 ，N端单铽转铁蛋白为简单的一次途径。NaCl的加入可促进两种单铽（III）的脱除 ，且C端铽转铁蛋白较N端单铽转铁蛋白更易受NaCl的影响。     

温度对铽（III）-转铁蛋白溶液构象的影响

在pH 7.4,0.01 mol/L N-2-羟乙基哌嗪-N’-2-乙磺酸（Hepes）条件下,铽 （III）与N,N’-二（2-羟苄基）乙二胺-N,N’-二乙酸（HBED）结合并发生交换 相互作用使铽（III）荧光增强10~4倍,通过监测铽（III）545 nm荧光强度的变化 测定了Tb-HBED配合物的条件稳定常数是lgK = 14.30 ± 0.49;Tb-HBED配合物中 配体、铽（III）荧光强度均随着温度的升高而降低。在pH 7.4,0.01 mol/L Hepes条件下,Tb_N-apoTf-Tb_C配合物中蛋白质的荧光强度随着温度的升高而降 低,而能量受体铽（III）的荧光强度随着温度的升高而增强,主要源于铽（III） 与螺旋5色氨酸残基间的无辐射能量转移;当温度由0 ℃上升到55 ℃时,平均能量 转移效率AE值增加了29%,给体、受体间距离R有约4.2%的减小,温度变化引起 Tb_N-apoTf-Tb_C配合物大的构象变化;铽（III）与人血清脱铁转铁蛋白的结合使 蛋白质的变性温度降低。同样条件下,Tb_N-apoOTf-Tb_C配合物与Tb_N-apoTf- Tb_C配合物有所不同,虽然能量给体的荧光强度随着温度的增加而减小,但铽（ III）荧光强度没有明显的增强;铽（III）对蛋白质的变性温度几乎没有影响。     

温度对铽（III）-转铁蛋白溶液构象的影响

在pH 7.4，0.01 mol/L N-2-羟乙基哌嗪-N’-2-乙磺酸（Hepes）条件下，铽 （III）与N，N’-二（2-羟苄基）乙二胺-N，N’-二乙酸（HBED）结合并发生交换 相互作用使铽（III）荧光增强10~4倍，通过监测铽（III）545 nm荧光强度的变化 测定了Tb-HBED配合物的条件稳定常数是lgK = 14.30 ± 0.49；Tb-HBED配合物中 配体、铽（III）荧光强度均随着温度的升高而降低。在pH 7.4，0.01 mol/L Hepes条件下，Tb_N-apoTf-Tb_C配合物中蛋白质的荧光强度随着温度的升高而降 低，而能量受体铽（III）的荧光强度随着温度的升高而增强，主要源于铽（III） 与螺旋5色氨酸残基间的无辐射能量转移；当温度由0 ℃上升到55 ℃时，平均能量 转移效率AE值增加了29%，给体、受体间距离R有约4.2%的减小，温度变化引起 Tb_N-apoTf-Tb_C配合物大的构象变化；铽（III）与人血清脱铁转铁蛋白的结合使 蛋白质的变性温度降低。同样条件下，Tb_N-apoOTf-Tb_C配合物与Tb_N-apoTf- Tb_C配合物有所不同，虽然能量给体的荧光强度随着温度的增加而减小，但铽（ III）荧光强度没有明显的增强；铽（III）对蛋白质的变性温度几乎没有影响。     

螯合剂对铽(Ⅲ)-转铁蛋白配合物的影响

在室温及ｐＨ７．４下,观察了一些螯合剂对铽（Ⅲ）－转铁蛋白配合物的影响．结果表明,铽（Ⅲ）与人血清脱铁转铁蛋白的结合是可逆的;ＥＤＴＡ和次氮基三乙酸可使铽（Ⅲ）－脱铁转铁蛋白配合物定量释放铽（Ⅲ）．用ＥＣＣＬＥＳ程序计算表明,血清中微摩尔数量级的铽（Ⅲ）主要以小分子配合物形式存在,其中铽（Ⅲ）－柠檬酸约占６２％,而铽（Ⅲ）－脱铁转铁蛋白配合物约占２１％     

铽配合物Tb(o-BBA)3(phen)有机电致发光研究

合成了一种新的稀土配合物邻苯甲酰苯甲酸-1，10-菲罗啉-铽（Tb（o-DDA）3（phen））并用于有机电致发光。研究了Tb（o-DDA）3（phen）与PVK混合薄膜的光敛发光特性，找出了PVK：Tb的最佳比例为3：1。制备了结构为ITO／PVK：Tb／Al的单层电致发光器件，得到了铽离子的特征光谱，其电流-电压特性（I-V）在一定电压范围内符合空间电荷限制电流机制。研究结果表明稀土铽配合物Tb（o-BBA）3（phert）掺杂PVK体系的光致发光是源于PVK到Tb配合物的能量传递及稀土Tb配合物的直接激发两种作用机制，而电致发光以载流子俘获为主。     

铽-依诺沙星荧光特性研究及应用

研究了铽-依诺沙星络合物的荧光特性,发现在近中性的HAc-NaAc缓冲溶液中,铽（Ⅲ）与依诺沙星反应形成1：2络合物,在紫外光照射下发生分子内能量传递而显铽离子的特征荧光,据此建立了一种以铽离子为荧光探针,简便、快速和灵敏的测定痕量依诺沙星的新方法。该方法用于人体尿药浓度的直接测定,平均回收率为98．7％-101．0％,相对标准偏差为0．3％～1．0％。     

温度对铽(Ⅲ)-转铁蛋白溶液构象的影响

在pH 7.4,0.01 mol/L N-2-羟乙基哌嗪-N′-2-乙磺酸(Hepes)条件下,铽(Ⅲ)与N,N′-二(2-羟苄基)乙二胺-N,N′-二乙酸(HBED)结合并发生交换相互作用使铽(Ⅲ)荧光增强104倍,通过监测铽(Ⅲ)545 nm荧光强度的变化测定了Tb-HBED配合物的条件稳定常数是lgK=14.30±0.49;Tb-HBED配合物中配体、铽(Ⅲ)荧光强度均随着温度的升高而降低.在pH 7.4,0.01 mol/L Hepes条件下,TbN-apoTf-Tbc配合物中蛋白质的荧光强度随着温度的升高而降低,而能量受体铽(Ⅲ)的荧光强度随着温度的升高而增强,主要源于铽(Ⅲ)与螺旋5色氨酸残基间的无辐射能量转移;当温度由0℃上升到55℃时,平均能量转移效率AE值增加了29%,给体、受体间距离R有约4.2%的减小,温度变化引起TbN-apoTf-Tbc配合物大的构象变化;铽(Ⅲ)与人血清脱铁转铁蛋白的结合使蛋白质的变性温度降低.同样条件下,TbN-apoOTf-Tbc配合物与TbN-apoTf-Tbc配合物有所不同,虽然能量给体的荧光强度随着温度的增加而减小,但铽(Ⅲ)荧光强度没有明显的增强;铽(Ⅲ)对蛋白质的变性温度几乎没有影响.     

吲哚羧酸与铽离子的作用及其构象研究

本文使用铽（Ⅲ）为荧光探针，探讨了吲哚－３－乙酸（ＩＡＡ）、吲哚－３－丙酸（ＩＰＡ）、吲哚－３－丁酸（ＩＢＡ）与铽（Ⅲ）的作用。基于Ｆｏｒｓｔｅｒ偶极－偶极无辐射能量传递机理，推算了结合铽（Ⅲ）与吲哚环的ＩＡＡ、ＩＰＡ、ＩＢＰ的距离，它们分别是７．９７Ａ，１０．２９Ａ，１２．５６Ａ。     

吸附法脱除乙烯中少量氮气的研究

采用重量法在电子天平上，研究了C2H4和N2单组分在5A、13X、丝光沸石和炭分子筛不同吸附剂上的吸附平衡性质和扩散动力学性质。单柱模拟变压吸附评价了炭分子筛吸附脱除C2H4-N2（N2为4．7％）混合组分中N2的性能，并对流速和压力的影响进行了考察。研究表明，该炭分子筛是吸附脱除C2H4中少量N2的理想吸附剂。     

螯合剂对稀土-转铁蛋白配合物的影响(Ⅱ)——稀土-转铁蛋白配合物的阴离子结合性质

在0.1mol/LHepes,pH 7.4 的条件下,使用紫外差谱和铽(Ⅱ)荧光光谱观察了一些螯合剂对稀土-转铁蛋白配合物REC-apoTf中RE的脱除.荧光滴定表明,螯合剂对TbC-apoTf中铽(Ⅱ)的脱除按缔合机理进行.当螯合剂为非伴阴离子时,脱除过程有TbC-apoTf-L三元配合物中间体生成;当螯合剂为伴阴离子时,脱除过程有L-TbC-apoTf三元配合物中间体生成;L-TbC-apoTf比TbC-apoTf-L更有利于脱除反应的进行;HEDTA,EDTA和NTA可定量地将TbC-apoTf转化为Tb-L或Tb-L2小分子配合物.     

Terbium(III) as fluorescence probe in the study of the interaction of rare earth and transition metal ions with concanavalin A

The binding site for calcium (II) on concanavalin A (con-A) can be occupied by rare earth ions. When terbium (III) ion binds to con-A, its fluorescence intensity is tremendously enhanced because of an energy transfer from one or more tryptophan residues in close proximity to the bound terbium (III). The dissociation constant of the con-A-Tb (III) complex is 8.90 × 10^?6M, obtained from terbium (III) fluorescence titration with con-A. The dissociation constant of the complexes of con-A with other rare earth and transition metal ions was obtained through their competition with terbium (III) in the reaction with con-A, i. e. the quenching of con-A enhanced fluorescence. The results indicate that the binding of rare earth ions with con-A is dependent not only on their ionic radius but also on the hard-soft acid-base strength of the metal ions.     

Hydrothermal Synthesis, Crystal Structure, and Characterization of a Novel Terbium(Ⅲ) Coordination Polymer Bridged by 5-Sulfoisophthalate Trivalent Anions

Hydrothermal reaction of terbium( Ⅲ ) chloride with 5-sulfoisophthalic acid monosodium salt and 1, 10-phenanthroline(phen) at 415 K resulted in the formation of a novel coordination polymer, [Tb(sip) (phen) (H2O)]n( sip = 5-sulfoisophthalate trivalent anion) with a three-dimensional network structure. Each centrosymmetrically related pair of terbium ions are linked by two sip anions, forming a binuclear unit, and each binuclear unit links to four adjacent tetranuclear units, extending a two-dimensional hybrid layer at crystallographic bc plane. On the other hand,every three-terbium ion is connected by three sip anions, generating a trinuclear ring, and the trinuclear ring connects six neighboring trinuclear rings to produce another two-dimensional layer at crystallographic ab plane. Moreover, each sip anion acts as a pentadentate bridge, interconnecting two different types of layers to yield a novel three-dimensional framework.     

Changes in hydration of lanthanide ions on binding to DNA in aqueous solution

The interaction of the trivalent lanthanides Ce(III), Eu(III), and Tb(III) with sodium deoxyribonucleic acid (DNA) in aqueous solution has been studied using their luminescence spectra and decays. Complexation with DNA is indicated by changes in luminescence intensity. In the system terbium(III)-DNA, changes in luminescence with pH are suggested to be due to the protonation of phosphate groups. The degree of hydration of Tb(III) on binding to DNA is followed by luminescence lifetime measurements in water and deuterium oxide solutions, and it is found that the lanthanide ion loses at least one hydration water on binding to long double stranded DNA at pH 4.7 and pH 7. Rather different behavior is observed on binding to long or short single stranded DNA, where six water molecules are lost, independent of pH. It is suggested that in this case the lanthanide probably binds to the bases of the DNA backbone. The DNA conformation seems to be an important factor in the binding. In addition, the isotopic effect on terbium luminescence lifetime may provide a useful method to distinguish between single and double stranded DNA. DSC results are consistent with cleavage of the double helix of DNA at pH 9 in the presence of terbium.     

Effect of ligand structure on the pathways for iron release from human serum transferrin

Rate constants for the removal of iron from N-terminal monoferric transferrin have been measured for a series of phosphate and phosphonocarboxylic acids in pH 7.4 0.1 M hepes buffer at 25 degrees C. The bidentate ligands pyrophosphate and phosphonoacetic acid (PAA) show a combination of saturation and first-order kinetics with respect to the ligand concentration. Similar results are observed following a single substitution at the 2-position of PAA to give 2-benzyl-PAA and phosphonosuccinic acid. In contrast, disubstitution at the 2-position to form 2,2-dibenzyl-PAA leads to a marked reduction in iron removal via the first-order pathway. Rate constants were also measured for tripolyphosphate and phosphonodiacetic acid, which are elongated versions of PP(i) and PAA. In both cases, this elongation completely eliminates the first-order component for iron release while having relatively little impact on the saturation pathway. The sensitivity of the first-order component to the structure of the ligand strongly indicates that this pathway involves the binding of the ligand to a specific site on the protein and cannot be attributed to changes in the overall ionic strength of the solution as the ligand concentration increases. It is proposed that this structural sensitivity reflects steric restrictions on the ability of the incoming ligand to substitute for the synergistic carbonate anion to form a relatively unstable Fe-ligand-Tf ternary intermediate, which then dissociates to FeL and apoTf.     

Reinvestigation of phase equilibria in TbCl<Subscript>3</Subscript>–LiCl binary system

The phase equilibria in the terbium(III) chloride–lithium chloride pseudobinary system were established by means of differential scanning calorimetry. It was established that the pure terbium(III) chloride undergoes solid–solid phase transition at 790 K and melts at 859 K. The TbCl₃–LiCl pseudobinary system is characterized by the existence of two compounds. First one, namely Li₃TbCl₆, forms at 553 K and melts incongruently at 727 K. Second compound, LiTbCl₄, decomposes in the solid state at 609 K. The composition of Li₃TbCl₆–TbCl₃ eutectic corresponding to terbium(III) chloride mole fraction x = 0.521 (T = 665 K) was found from Tammann plot, which predict, through application of the lever rule, the variation of the enthalpy associated with eutectic melting as a function of composition. The obtained results have been compared with the literature data concerning for the TbCl₃–LiCl pseudobinary system. The phase diagram of the TbCl₃–LiCl pseudobinary system was also optimized by CALPHAD method.     

Cyano-bridged terbium(III)-chromium(III) bimetallic quasi-one-dimensional assembly exhibiting long-range magnetic ordering

A new cyano-bridged Tb(III)-Cr(III) heterometallic complex [Tb(H(2)O)(2)(DMF)(4){Cr(CN)(6)}]·H(2)O (DMF = dimethylformamide) (1), assembled from paramagnetic hexacyanochromium(III) [Cr(CN)(6)](3-) building block and highly anisotropic terbium(III) ion has been prepared and structurally and magnetically characterized. Complex 1 shows one-dimensional (1D) zig-zag chain-like structural motif which is further extended into three-dimensional network through hydrogen-bonding interactions. The long-range magnetic ordering observed in complex 1, which is possibly due to interchain magnetic dipolar interactions, illuminates that this complex is a molecule-based magnet with critical temperature of about 5 K. This higher critical temperature among those of Ln(III)-Cr(III) heterometallic complexes exhibiting long-range magnetic ordering is probably due to the introduction of highly anisotropic terbium(III) ion.     

A new luminescence method for determining dysprosium in the presence of terbium

The new luminescence method for determining dysprosium in the presence of terbium is developed based on the difference in the lifetimes of dysprosium and terbium in complexes with 3-(6-benzodioxanyl)pyrazole-5-carboxylic acid (τ = 6 and 910 μs, respectively). The possibility of determining the short-lived and weakly luminescent dysprosium(III) ion in the presence of long-living and intensively luminescent terbium(III) was demonstrated for the first time using time-resolved luminescence. The developed method was used to determine dysprosium in luminescent materials doped with both lanthanides.     

Kinetic demonstration of the intramolecular nature of the rearrangement of aromatic N-nitroso-amines (Fischer-Hepp)

Rate equations have been deduced for two possible mechanisms for the reactions of N-methyl-N-nitrosoaniline in acid solution, namely, (1) for the generally accepted intermolecular mechanism which involves denitrosation followed by C-nitrosation and (2) a mechanism involving intramolecular rearrangement which takes place concurrently with denitrosation. The observed rate constants obtained under various experimental conditions are consistent only with mechanism (2). In particular the question of halide ion catalysis differentiates clearly between the two mechanisms. Mechanism (1) predicts a first-order dependence upon chloride (or other halide) ion under all conditions, whereas (2) allows a first-order chloride ion dependence only in the presence of a large excess of a “nitrite trap” such as sulphamic acid, urea, hydrazoic acid, hydroxylamine, etc., whereas at the other limit of high concentration of added N-methylaniline, the rate constants should be independent of the halide ion concentration. The predictions based on mechanism (2) are all borne out by experiment.     

A dinuclear lanthanide complex for the recognition of bis(carboxylates): formation of terbium(III) luminescent self-assembly ternary complexes in aqueous solution

The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear terbium complex, 2.Tb(2), that can detect the presence of mono- or bis(carboxylates) in buffered aqueous solution at physiological pH is described. Full ligand synthesis and structural characterization of 2.Na(2) are also described. Spectroscopic measurements determined that each Tb(III) metal center has two metal-bound water molecules (q = 2). The recognition or sensing of N,N-dimethylaminocarboxylic acid, 4, and the bis(carboxylate) terephthalic acid, 5, which can also function as sensitizing antennae, was found to occur through the binding of these carboxylates to the metal center via the displacement of the metal bound water molecules. This gave rise to the formation of luminescent ternary complexes in solution in 2:1 or 1:1 (ion:2.Tb(2)) stoichiometry, respectively. Aliphatic bis(carboxylates) also bind to 2.Tb(2) where the selectivity for the ion recognition and stoichiometry was dictated by the structure of the anion, being most selective for pimelic acid, 6. Binding of either l- or d-tartaric acid gave rise to the formation ternary complex formation, with 2:1 stoichiometry, where the ion recognition resulted in quenching of the lanthanide emission.     

Lanthanide luminescent anion sensing: evidence of multiple anion recognition through hydrogen bonding and metal ion coordination

The delayed lanthanide luminescence of the terbium [Tb(III)] diaryl-urea complex 1xTb is significantly enhanced upon sensing of dihydrogenphosphate (H2PO4(-)) in CH3CN, which occurs through multiple anion binding through hydrogen bonding interactions and potential metal ion coordination to Tb(III).