铕(III)离子与人血清脱铁转铁蛋白结合的紫外差光谱研究

在pH7.4,温度为25℃的条件下,用紫外吸收差光谱进行了Eu^3^+对人血清脱铁转铁蛋白的滴定。结果表明Eu^3^+与人血清脱铁转铁蛋白结合后其差光谱在245nm和296nm处出现吸收峰,在245nm处,Eu^3^+-脱铁转铁蛋白配合物的摩尔吸光系数是(2.2±0.1)×10^4cm^-^1.mol^-^1.dm^3,Eu^3^+可占据脱铁转铁蛋白的2个金属离子结合部位,Eu^3^+优先占据脱铁转铁蛋白的C端结合部位,条件平衡常数是logK~C=8.42±0.12,logK~N=6.03±0.42。Eu^3^+与R~E^3^+(R~E=Nd,Sm,Gd和Tb)间的线性自由能关系表明,稀土离子占据脱铁转铁蛋白的C端结合部位时受离子大小的影响。     

稀土离子与伴清蛋白结合的紫外差光谱研究

在ｐＨ７．４ ,２５ ℃的条件下, 使用紫外吸收差光谱进行了Ｅｕ３＋ ,Ｔｂ３＋ ,Ｌｕ３＋ 对脱铁伴清蛋白的滴定。结果表明, 稀土离子与脱铁伴清蛋白结合后其差光谱均在２４４ 和２９４ ｎｍ 处给出吸收峰, 在２４４ ｎｍ 处, 稀土离子脱铁伴清蛋白络合物的摩尔吸光系数相近, 约为（２．１ ±０．１） ×１０４ ｃｍ －１·ｍｏｌ－ １·Ｌ;稀土离子可占据脱铁伴清蛋白的两个金属离子结合部位, 但优先占据脱铁伴清蛋白的Ｎ端结合部位。Ｃ端结合部位与稀土离子的结合量受ＣＯ２ －３ 浓度及离子半径的影响, 离子半径越大、ＣＯ２－３ 浓度越高,稀土离子在该部位的结合量越少。     

铝(Ⅲ)与脱铁伴清蛋白结合的紫外差光谱研究

在 pH7.4、 0.1mol· L~(－1)N-2-羟乙基哌嗪- N′-2-乙磺酸（ Hepes）及室温条件下,使用紫外吸收差光谱进行了铝(Ⅲ)对脱铁伴清蛋白的滴定。结果表明铝(Ⅲ)与脱铁伴清蛋白结合后其紫外差光谱在 238nm和 291nm处出现吸收峰。在 238nm处铝(Ⅲ)-脱铁伴清蛋白配合物的摩尔吸光系数是 (1.52± 0.04)× 10~4cm~(－1)· mol~(－1)· L。铝(Ⅲ)可占据脱铁伴清蛋白的两个金属离子结合部位,条件稳定常数是 lgK_N=11.21± 0.12,lgKC=9.53± 0.24。 N-端单铁伴清蛋白的紫外差光谱滴定表明,铝 ?优先占据脱铁伴清蛋白的 N端结合部位。     

稀土离子与伴清蛋白结合的光谱研究

在ｐＨ＝７．４和２５℃下，用紫外吸收差光谱进行了Ｅｕ＾３＋对脱伯伴清蛋白的滴定，Ｅｕ＾３＋与脱铁伴清蛋白结合后其差光谱在２４５ｎｍ和２９６ｎｍ处出现吸收峰，在２４５ｎｍ处Ｅｕ＾３＋脱铁伴清旧白配合物的摩尔吸光系数是（２．１±０．１）×１０＾４ｃｍ＾－１．Ｌ．ｍｏｌ＾－１，Ｅｕ＾３＋可占据脱铁伴清蛋白的２个金属离子结合部位，条件平衡常数ｌｏＫＮ＝８．２１±０．２０，ｌｇＫｃ＝４．６０±０．１１，脱铁     

稀土离子与乳铁蛋白结合的光谱研究

用紫外示差光谱、荧光光谱及圆二色谱等方法研究了Tb³⁺和Eu³⁺在pH7.4的条件下与乳铁蛋白及脱铁乳铁蛋白的结合作用.结果表明,Tb³⁺及Eu³⁺可特异性地结合在脱铁乳铁蛋白的两个Fe³⁺结合部位,但不能从已经结合铁的乳铁蛋白中把铁置换出来.测得Tb³⁺ 与这两个部位结合的条件平衡常数为lgK₁=8.48±0.24和lgK₂=6.72±0.18(25℃,0.10mol/L NaCl, 0.10mol/LHepes,pH=7.4). Tb³⁺在这两个位点结合时,蛋白质的构象发生变化.在 Tb³⁺ 与蛋白质的浓度比低时,构象趋于紧缩,色氨酸残基进入疏水的环境;当Tb³⁺结合得较多时,构象转而开放,色氨酸残基转向亲水性环境.但无论哪种情况,Tb³⁺与脱铁乳铁蛋白的结合都不影响蛋白的二级结构.     

Eu:GGG纳米荧光粉体制备及其光学特性

采用液相共沉淀方法并在不同烧结温度下制得了Eu：GGG荧光粉体。用X射线衍射分析了样品的结构，计算了其晶格常数，为1．2371nm。室温下，测量了Eu：GGG的光致发射光谱、激发光谱和荧光衰减曲线。激发光谱在波长240～287nm的谱带内和393。。处有强的激发，分别来自于Eu^3＋O2^-间的电荷迁移态吸收和Eu“的^7F0→^5L6的跃迁吸收，同时在274nm处也出现了Gd^3＋的^8S7/2→^6I1的特征吸收。393nm激发下，591nm处的发射峰最强，对应Eu^3＋的^5D0→^7F1的磁偶极跃迁，可能由于部分Eu^3＋处于反演中心对称格位所致。随着烧结温度升高，Eu：GGG的发光强度增强，这可能由于随着烧结温度升高，样品晶粒尺寸变大，单位体积内被激发的Eu^3＋离子数增加引起，而591nm发光的荧光寿命变短，可能是由Eu^3＋离子的能量共振传递过程中发光被陷阱捕获所致。     

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％     

新型铕双β-二酮红光材料的合成与发光性质

通过分子设计,合成了一种新颖的双β-二酮有机配体9-乙基-3,6-二（乙酰基-3-苯甲酰基）咔唑（H2L）及其铕配合物,红外光谱和电子光谱表明Eu^3＋与H2L发生配位。配合物的溶液荧光光谱不仅有613 nm处的中心离子Eu^3＋的特征红光,属^5D0→^7F2跃迁带,还有445nm处配体的宽带蓝色发光,属H2L^＊→H2L跃迁带,而配合物的光致发光光谱只有611 nm处为中心离子Eu^3＋的特征红光,属^5D0→^7F2跃迁带,峰形尖锐,半峰宽仅7 nm,单色性好,表明该固体铕双β-二酮配合物是一种潜在的红色发光材料。     

Eu^3+和Eu^3+在LnBaB~9O~16是的紫外和真空卜外发光性质

研究了Tb^3+和En^3+在LnBaB~9O~16(Lu=La,Gd,Y,Lu)中的卜外和真空紫外光谱性质。X射线粉未衍射数据脂标化结果表明,LnBaB~9O~16(Lu=La,Gd,Y,Lu)系列化合物属于三方晶系。Eu^3+的荧光光谱结果表明,LnBaB~9O~16和GdBaB~9O~16中稀土离子占据非是心对称的格位,Eu^3+在其中的特征发射5D0→7F2电偶极跃迁为主;而在YBaB9O16和LuBaB9O16中稀土离子占据中心对称性的格位,Eu3^+在其中的特征发射以5D0→7F1磁偶极跃迁为主.     

Eu^3+和Eu^3+在LnBaB~9O~16是的紫外和真空卜外发光性质

研究了Tb^3+和En^3+在LnBaB~9O~16(Lu=La,Gd,Y,Lu)中的卜外和真空紫外光谱性质。X射线粉未衍射数据脂标化结果表明,LnBaB~9O~16(Lu=La,Gd,Y,Lu)系列化合物属于三方晶系。Eu^3+的荧光光谱结果表明,LnBaB~9O~16和GdBaB~9O~16中稀土离子占据非是心对称的格位,Eu^3+在其中的特征发射5D0→7F2电偶极跃迁为主;而在YBaB9O16和LuBaB9O16中稀土离子占据中心对称性的格位,Eu3^+在其中的特征发射以5D0→7F1磁偶极跃迁为主.     

链酚胺型配体锌(Ⅱ)配合物模拟碳酸酐酶研究

合成了酚胺型链状配体,N,N'-二(2-羟基苄基)丙二胺(H~2L)及其Zn(Ⅱ)配合物(ZnL),通过元素分析、IR和^1HNRM等手段进行了表征。采用pH电位滴定法,在25℃±0.1℃,I=0.1mol·dm^-^3(KNO~3)条件下,测定了配体的质子化常数以及配体与金属离子Zn(Ⅱ)配位反应平衡常数。讨论了配体与金属离子Zn(Ⅱ)的配位情况,得到了配位酚羟基的解离常数。运用分光光度法,在25℃±0.1℃,I=0.1mol·dm^-^3(KNO~3)条件下,在pH=5.5～9.0(50mmol·dm^-^3缓冲溶液)范围内,研究了配合物作为碳酸酐酶模拟物催化对-硝基苯酚乙酸酯(NA)水解动力学,得到了NA酯水解的配合物催化速率常数k~N~P。实验结果表明,ZnHL^+的配位酚羟基的解离常数pK~a为6.83;催化速率常数k~N~P与pH之间不存在Sigmoidal型曲线关系,而是在pH值中性附近有最大值,ZnHL^+对NA酯水解有很好的催化效果,并且采取双重催化机理,是碳酸酐酶很好的模拟物。     

Temperature dependence of europium carbonate complexation

The temperature dependencies of europium carbonate stability constants were examined at 15, 25, and 35°C in 0.68 molal Na⁺(ClO ₄ ^? , HCO ₃ ^? ) using a tributyl phosphate solvent extration technique. Our distribution data can be explained by the equilibria $$\begin{gathered} Eu^{3 + } + H_2 O + CO_2 (g)_ \leftarrow ^ \to EuCO_3^ + + 2H^ + \hfill \\ - log\beta _{12} = 9.607 + 496(t + 273.16)^{ - 1} \hfill \\ Eu^{3 + } + 2H_2 O + 2CO_2 (g)_ \leftarrow ^ \to Eu(CO_3 )_2^ - + 4H^ + \hfill \\ - log\beta _{24} = 21.951 + 670(t + 273.16)^{ - 1} \hfill \\ Eu^{3 + } + H_2 O + CO_2 (g)_ \leftarrow ^ \to EuHCO_3^{2 + } + H^ + \hfill \\ - log\beta _{11} = 1.688 + 1397(t + 273.16)^{ - 1} \hfill \\ \end{gathered}$$      

Aluminum Lon Removal from Monoaluminum Ovotransferrin by Pyrophosphate

The rates at which aluminum was removed from the N- and C-terminal monoaluminum ovotransferrins by pyrophosphate were evaluated by UV difference spectra in 0.01 mol/L Hepes, pH=7.4 and at 37℃. Pesudo first-order rate constants as a function of pyrophosphate concentration were measured. The results indicate that the pathways of aluminum removal are different. For the N-terminal binding site, aluminum removal follows simple saturation kinetics, while the removal of aluminum from the C-terminal binding site reverts to the combination of saturation and first-order kinetics. The saturation component is consistent with a rate-limiting conformational change in the protein as has been reported. We propose that the first-order kinetics mechanism is attributed to a pre-equilibrium process. The rate constants of saturation kinetics are accelerated from both terminals with the addition of 0.1 mol/L chloride to the monoaluminum ovotransferrin solutions, whereas the rates of the first-order kinetics are decreased for the C-terminal binding site. The effect of chloride ionic strength causes a continuing increase on kobs for the N- and C-terminal binding sites. Moreover, the kinetics behavior of the N-terminal is more easily affected by chloride than that of the C-terminal. In the experiment presumably the N-terminal site is apparently kinetically more labile than the C-terminal site.     

双冠醚配位作用的热力学性质V. 双(苯并-15-冠-5)与稀土(III)硝酸盐在无水乙腈溶液中分子内夹心配位作用

本文用分光光度滴定法测定了双(苯并-15-冠-5)(1)与轻稀土(III)硝酸盐在无水乙腈溶液中, 20.0-35.0℃时分子内夹心配位作用的稳定常数, 进而计算了配位焓和配位熵, 并与母体苯并15-冠-5(2)的实验结果作了比较。化学计量法表明, 所有稀土硝酸盐均与双(苯并-15-冠-5)形成了1 : 1的配合物。从热力学的观点, 讨论了双冠醚分子结构、尺寸效应和空间构型等配位稳定性的影响。研究结果发现, 双冠醚(1)对于Eu^3^+具有较强的配位能力和配位选择性, Nd^3^+次之。配合物的稳定性主要来自于熵的贡献。     

The binding of Ca2+ and Mg2+ to human serium albumin: A calorimetric study

The binding of calcium and magnesium to human serum albumin has been studied in the pH region 2.5–8.0 by a calorimetric procedure. Both metal ions bind to the carboxylate groups of albumin. 36 and 44 carboxylate groups appear to be involved in the binding of Ca²⁺ and Mg²⁺, respectively. Based on previously reported results that twelve Ca²⁺ ions are the maximum which can bind to albumin, the results given here support previous X-ray crystallographic evidence that three carboxylate groups can be involved in the binding of a Ca²⁺ by a protein. The data also confirm that Ca²⁺ and Mg²⁺ binding is competitive. Binding of the cations to the carboxylate groups appears to involve the breaking of carboxylate-imidazole hydrogen bonds in the protein. Log K, ΔH and ΔS values obtained for the binding of metal ions to albumin in aqueous solution at 25°C are 2.72 ± 0.02, 0.0 ± 0.1 kcal/mole, and 12.4 ± 0.3 cal/mole K for Ca²⁺ and 1.12 ± 0.05, ?0.2 ± 0.1 kcal/mole, and 4.5 ± 0.3 cal/mole K for Mg²⁺, respectively.     

MMgF4(M=Ca,Sr, Ba)体系中Eu和Tb的电荷迁移

于不同气流中, 合成了MMgF4:xEu,yTb复合氟化物磷光体。该体系中Eu^3^+和Eu^2^+共存。Tb的存在影响Eu的价态存在形式。ESR测试表明, 随Tb的掺入浓度增加, Eu^2^+的浓度呈规律性变化。随Eu的掺入, 样品的XPS谱中出现了四价铽的Tb3d5/2特征伴峰。认为Eu^3^+和Tb^3^+之间存在电荷迁移平衡。即Eu^3^++Tb^3^+=Eu^2^++Tb^4^+。通过半定量手段研究了SrMgF4中这一衡的平衡常数。     

利用荧光浓度指示剂fura-2研究稀土离子的跨膜行为

本文提出了利用fura-2测量细胞内游离稀土离子浓度的定量方法。实验结果表明, 在模拟细胞内离子组成的条件下, 稀土离子La^3^+和Y^3^+与fura-2形成1:1的配合物。其配合物的表观离解常数分别为161nmol.dm^-^3和404nmol.dm^-^3,pH7.05, 有未配对f电子的Nd^3^+, Ho^3^+, Sm^3^+, Dy^3^+,Ce^3^+, Yb^3^+等稀土离子对荧光起萃灭作用。此性质使我们能够定性鉴定它们是否进入了细胞。我们使用如上性质, 利用单细胞阳离子测试系统, 以小鼠骨髓瘤细胞为模式细胞, 研究了上游离稀土离子的跨膜行为及部分体内小分子对稀土离子跨膜行为的影响。实验结果支持游离稀土离子不能通过细胞膜的假设, 而且所研究的体内小分子在生理浓度下对稀土离子的跨膜也无明显作用。     

Thermodynamic Complexation of Dopamine with Zinc(II) in Media with Different Dielectric Constants

The complexation of zinc(II) with dopamine has been investigated by spectrophotometric measurements in mixed solvent system at an ionic strength of 0.2 mol•dm－3 sodium chloride, employed at at (15±0.1), (25±0.1), (35±0.1) ℃ at inin a pH range of ca. 6 to ca. 7 with a high ratio of ligand to metal. The effect of solvent systems on protonation and complexation are was was discussed. Linear relationships are werewere observed by plotting lg K versus 1/D, where K and D show stability and dielectric constants, respectively.     

Connecting simulated,bioanalytical, and molecular docking data on the stereoselective binding of (±)-catechin to human serum albumin

The stereoselective binding of the frequently ingested nutraceutical (±)-catechin, with demonstrated differential biological activity between enantiomers, to human serum albumin (HSA), with the largest complexation and enantioselectivity potential among the plasmatic proteins, is studied by combining simulations to optimize the experimental design, robust in vitro electrokinetic chromatographic data, and molecular docking–chiral recognition estimates. Methodological and mathematical drawbacks in previous reports on (±)-catechin–HSA are detected and eliminated. Recent and novel direct equations extracted from the classical interaction model allows advantageous univariate mathematical data treatment, providing the first evidence of quantitative (±)-catechin–HSA enantioselectivity. Also, the binding site in HSA of the enantiomers is approached, and both the experimental enantioselectivity and the main binding site information are contrasted with a molecular docking approach.