稀土与脂肪族Schiff碱多核配合物的合成及波谱

在形成多核配合物的诸条件中,认为减小空间位阻颇为重要,设计的直链脂肪族的四甘醇醛与甘氨酸缩合形成的Schiff碱(TAGL)为此提供了有利的条件,且成功地获得了它与稀土离子反应形成的三核配合物(Ln:L=3:1):[Ln~3(TAGL)(NO~3)~7]CH~3OH·nH~2O(Ln=La,Nd,Sm,n=1;Ln=Gd,Dy,Yb,Y,n=2)。以元素分析,IR,NMR等确证其组成,根据EPR谱探讨了Gd(III)配合物的晶体场强,同时见到该类脂肪族Schiff碱及其配合物中δ~H~C~=~N的质子谱向高场明显位移至～5.10。     

重水溶液中稀土-吡啶-2,6-二羧酸配合物的第二配位圈^1HNMR顺磁位移

对稀土-吡啶-2,6-二羧酸(DPA)配合物Ln(DPA)3进行了NMR研究并观察到了由溶剂分子形成的第二配位圈的顺磁位移效应.     

外消旋丙—丝二肽及其稀土配合物的NMR性质

不同ｐＨ值下的Ｄ，Ｌ－丙氨酰－Ｄ，Ｌ－丝氨酸及其稀土配合物的＾１Ｈ，＾１３ＣＮＭＲ谱，对于该种二肽的不同旋光异构体，有可能对其谱线进行区分和指认。测定了酸解常数和稀土配合物的络合稳定常数。通过分离Ａｌａ－Ｓｅｒ的重稀土配合物的接触位移和偶极位移。分析了不同异构体配合物的ＮＭＲ位移的原因。     

有生物活性的稀土-腺苷三磷酸系列物的合成及其量子化学理论计算的研究

本文首次报道合成了稀土-腺苷三磷酸固态配合物RE(Ⅲ)-ATP(RE=Y、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu)。运用红外、激光Raman、热分析、紫外、顺磁、X射线衍射、元素分析、配位滴定等技术测定了上述配合物的化学组成和分子结构,其分子式用通式表为[RE(Ⅲ)(HATP)(H_2O)_4]。采用量子化学INDO方法计算了系列物的电子结构,依据计算结果讨论了生物化学中高能磷酸键的本质。     

蛋氨酸稀土配合物构象的^13CNMR研究

本文测量了在7种不同稀土离子(La~(3 )、Pr~(3 )、Nd~(3 )、Dy~(3 )、Ho~(3 )、Er~(3 )和Tm~(3 ))的水溶液中蛋氨酸~(13)C稀土诱导位移。利用稀土诱导位移对蛋氨酸稀土配合物构象的模拟结果表明,蛋氨酸通过离子化的羧基与稀土离子配位,Ln~(3 )—O长度为2.7A在配合物中,蛋氨酸以伸展状态存在,C_0-C_α-C_β-C_γ和C_α-C_β-C_γ-S成反式构象,C_β-C_γ-S-C_δ成旁式构象。根据稀土诱导位移方法建立的构象模型符合~1H邻位质子偶合常数和~(13)C顺磁弛豫速率的结果。     

双甘肽稀土配合物溶液结构的~(13)C~1H NMR研究

关于双甘肽的~(13)C化学位移行为及其与稀土离子的配位作用前人有过报导。但有关水溶液中双甘肽稀土配合物的结构仍不清楚。本文测定了在重稀土离子Dy~(3+)、Ho~(3+)、Er~(3+)、Tm~(3+)和Yb~(3+)作用下双甘肽~(13)C和~1H的顺磁诱导位移,研究了水溶液中双甘肽稀土配合物的组成及结构。1 实验部分     

稀土冠醚类配合物的研究 XX: 三价及二价稀土硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)配合物的合成和性质

在乙腈和二氯甲烷混合溶液中合成了三价稀土元素(La, Nd, Eu, Dy, Er, Yb)硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)的六个新配合物。并在氩气氛中, 以四氢呋喃为溶剂, 锂-萘为还原剂, 制得了二价铕硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)的固体配合物。通过元素分析、红外光谱、差热热重分析、荧光光谱、穆斯堡尔谱、电子自旋共振谱、还原性实验等研究了双冠醚与稀土离子的配位作用, 并讨论了三价和二价稀土配合物在物理化学性质上的差别。     

稀土与三甘酸固态配合物的研究

在水溶液中合成了一系列稀土与三甘酸的因态配合物，元素分析、摩尔电导、红外光谱、紫外光谱、热分析及核磁共振谱证明，配合物的组成为ＲＥ２。推测配合物是配位数为９的双核结构，羧基以螯合双齿形式配位，两个醚氧原子均参与配位，结晶水数为３。同时用不同浓度下配合物的＾１ＨＮＭＲ谱研究了浓度对化学位移的影响。     

稀土冠醚类配合物的研究 XX: 三价及二价稀土硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)配合物的合成和性质

在乙腈和二氯甲烷混合溶液中合成了三价稀土元素(La, Nd, Eu, Dy, Er, Yb)硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)的六个新配合物。并在氩气氛中, 以四氢呋喃为溶剂, 锂-萘为还原剂, 制得了二价铕硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)的固体配合物。通过元素分析、红外光谱、差热热重分析、荧光光谱、穆斯堡尔谱、电子自旋共振谱、还原性实验等研究了双冠醚与稀土离子的配位作用, 并讨论了三价和二价稀土配合物在物理化学性质上的差别。     

混合物中稀土元素的NMR法测定

核磁共振检测混合物中的共存金属是新近发展起来的无机分析方法。Fedorov以EDTA和NTA为配体,通过观察络合物Ln(EDTA)和Ln(NTA)_2配体的~1H NMR谱线,率先开展了水溶液中共存稀土元素的同时间接测定研究,这种方法比分别直接检测各稀土核磁核共振信号的方法实用可靠,且方便易行。但采用~1H NMR谱检测水溶液中顺磁稀土离子时,强的溶剂水峰易掩蔽近邻的稀土配合物谱线;某些重稀土配合物的~1H谱线宽,相互重叠,难以用作分     

Conformational study of L-lysine in aqueous solution by lanthanide shift probes

Conformation of L-lysine in aqueous solution was investigated by lanthanide shift probes (Dy, Ho, Er, Tm and Yb). Reilley's method was employed to separate the contact and dipolar components of the ¹³C paramagnetic shifts. This study reveals that Cα shift has the largest contact contribution while the other carbon shifts are dominated by the dipolar contribution. The average overall conformation of L-lysine in aqueous solution is extended with the molecular backbone in trans form. In the complex, lanthanide ion coordinates to the carboxyl group with Ln—O bond length 2.2 Å and the whole ligand is located outside the zero-dipolar shift cone of the lanthanide ion. The electronic spin density distribution on the ligand nuclei shows that the spin polarization is the predominant mechanism of the contact interaction for nuclei in close proximity to the bound lanthanide ion.     

1H and 13C NMR studies of lanthanide complex with 5-sulfosalicylic acid

In this paper, paramagnetic shifts have been measured for all ¹H and ¹³C nuclei of 5-sulfosalicylic acid (SSA) in the presence of the lanthanide ions in the second half of the series. The ligand forms isostructural complexes with these ions in aqueous solution. The separation of LISs was carried out by the use of the Reilley method and the calculated dipolar shifts were used to simulate the coordination structure of the complex. The result reveals that SSA is coordinated to lanthanide ion via two oxygens, one from the carboxylic group and the other from the phenolic group with Ln–O bond lengths equal to 2.47 Å. The lanthanide ion lies on the benzene plane and the carboxylic group is twisted 20° from the benzene ring. Of all the nuclei examined, those in the six-membered chelate ring experience significant dipolar interactions and contact interactions. Small |G/A| ratios were obtained for two protons five bonds away from the central lanthanide ion, which shows that the number of bonds alone cannot be used as a criterion for neglecting contact shifts in aromatic ligand.     

Structure determination of protein-ligand complexes by transferred paramagnetic shifts

Rational drug design depends on the knowledge of the three-dimensional (3D) structure of complexes between proteins and lead compounds of low molecular weight. A novel nuclear magnetic resonance (NMR) spectroscopy strategy based on the paramagnetic effects from lanthanide ions allows the rapid determination of the 3D structure of a small ligand molecule bound to its protein target in solution and, simultaneously, its location and orientation with respect to the protein. The method relies on the presence of a lanthanide ion in the protein target and on fast exchange between bound and free ligand. The binding affinity of the ligand and the paramagnetic effects experienced in the bound state are derived from concentration-dependent (1)H and (13)C spectra of the ligand at natural isotopic abundance. Combined with prior knowledge of the crystal or solution structure of the protein and of the magnetic susceptibility tensor of the lanthanide ion, the paramagnetic data define the location and orientation of the bound ligand molecule with respect to the protein from simple 1D NMR spectra. The method was verified with the ternary 30 kDa complex between the lanthanide-labeled N-terminal domain of the epsilon exonuclease subunit from the Escherichia coli DNA polymerase III, the subunit theta, and thymidine. The binding mode of thymidine was found to be very similar to that of thymidine monophosphate present in the crystal structure.     

Optical absorption and NMR spectroscopic studies on paramagnetic trivalent lanthanide complexes with 2,2'-bipyridine.; The solvent effect on 4f-4f hypersensitive transitions

The optical absorption and NMR studies of trivalent lanthanide chloride complexes with 2,2'-bipyridine (bpy) are presented and discussed. The NMR spectra of paramagnetic complexes exhibit lower as well as higher field shifts of bpy resonances that reflect change in geometry and reveals importance of the factor (3 cos2 theta - 1 ) in changing sign of the shift. The paramagnetic shifts recorded have been analyzed and the intramolecular shift ratios suggest that the paramagnetic shift is predominantly dipolar in origin. Electronic spectral studies of the Pr, Nd, Ho, Er and Dy complexes in different solvents (viz. methanol, pyridine, DMSO and DMF), which differ with respect to donor atoms, reveal that the chemical environment around the lanthanide ion has great impact on f-f transitions and any change in the environment results in modifications of the spectra. The oscillator strength for the hypersensitive and non-hypersensitive transitions have been determined and changes in the oscillator strength and band shape with respect to solvent type is rationalized in terms of ligand (solvent) structure and coordination properties.     

Beyond Bleaney's Theory: Experimental and Theoretical Analysis of Periodic Trends in Lanthanide‐Induced Chemical Shift

A detailed analysis of paramagnetic NMR shifts in a series of isostructural lanthanide complexes relavant to PARASHIFT contrast agents reveals unexpected trends in the magnetic susceptibility anisotropy that cannot be explained by the commonly used Bleaney's theory. Ab initio calculations reveal that the primary assumption of Bleaney's theory—that thermal energy is larger than the ligand field splitting—does not hold for the lanthanide complexes in question, and likely for a large fraction of lanthanide complexes in general. This makes the orientation of the magnetic susceptibility tensor differ significantly between complexes of different lanthanides with the same ligand: one of the most popular assumptions about isostructural lanthanide series is wrong.     

水溶液中甘氨酰-缬氨酸与稀土配位作用及其配合物构象的NMR研究

本文测定了在三种不同稀土离子(镧La^3^+、钬Ho^3^+和镱Yb^3^+)的水溶液中甘氨酰-缬氨酸的^1H的^1^3C稀土诱导位移。计算了Ho、Yb与甘氨酰-缬氨酸配合物的稳定常数, 讨论了稀土与该配体的配位作用及对配合物构象进行了研究, 发现配位后的甘氨酰-缬氨酸以一种空间位阻较小的伸展构象存在。     

Etude des Dérivés de la Vitamine B6. Conformation des Complexes de Lanthanides avec le Pyridoxal-5′-phosphate et la Pyridoxamine-5′-phosphate en Phase Aqueuse à pD = 1,3

A suitable procedure is described for establishing the conformational analysis of flexible molecules coordinated to lanthanide cations from ¹H and ¹³C NMR paramagnetic shift data. The examples of pyridoxal 5′-phosphate (PLP) and pyridoxamine 5′-phosphate (PMP) in aqueous solution at pD = 1.3 values are discussed. In the two cases, a hindered rotation around P? O-5′, with Gaussian distribution is proposed. The values of angles and distances between rare earth cations and ligand nuclei are determined.     

Backbone-only protein solution structures with a combination of classical and paramagnetism-based constraints: a method that can be scaled to large molecules.

Herein, it is shown that a medium-resolution solution structure of a protein can be obtained with the sole assignment of the protein backbone and backbone-related constriants if a derivative with a firmly bound paramagnetic metal is available. The proof-of-concept is provided on calbindin D9k, a calcium binding protein in which one of the two calcium ions can be selectively substituted by a paramagnetic lanthanide ion. The constraints used are HN (and Ha) nuclear Overhauser effects (NOEs), hydrogen bonds, dihedral angle constriants from chemical shifts, and the following paramagnetism-based constraints: 1) pseudocontact shifts, acquired by substituting one (or more) lanthanide(s) in the C-terminal calcium binding site; 2) N-HN residual dipolar couplings due to self-orientation induced by the paramagnetic lanthanide(s); 3) cross-correlations between the Curie and internuclear dipole-dipole interactions; and 4) paramagnetism-induced relaxation rate enhancements. An upper distance limit for internuclear distances between any two backbone atoms was also given according to the molecular weight of the protein. For this purpose, the paramagnetism-based constraints were collectively implemented in the program CYANA for solution structure determinations, similarly to what was previously done for the program DYANA. The method is intrinsically suitable for large molecular weight proteins.     

13C NMR study of D-pantothenic acid complexes with heavy lanthanide ions in aqueous solution

The ¹³C NMR study of the interaction between the trivalent lanthanide ions (from Dy to Lu) and D-pantothenic acid in aqueous solution was presented. The unambiguous resonance assignments were made on the basis of pH dependence and the analysis of molecular geometry. ¹³C paramagnetic shifts were separated into the contact and dipolar components by Reilley's method. The complex stability constant is 12.0 L / mol for the 1:1 ytterbium complex. An analysis of the shift data shows that heavy lanthanide ions form isostructural complexes with the substrate and the hyperfine coupling constant is independent of the ions used in the study. D-pantothenic acid is coordinated to the metal via the two oxygens of the carboxyl group with 2.25Å of Ln—O distances. The electron spin density distribution and the structural details of the complex were elucidated from the shift data. It is stated that contact contributions, while small for nuclei of several bonds away from the metal, should not be dismissed a priori.     

^1^3C NMR研究稀土柠檬酸配合物的溶液配位结构

用稀土离子诱导位移和顺磁弛豫时间测定等NMR方法研究了稀土柠檬酸配合物在pH 7.4的溶液中的配位结构。结果表明稀土离子通过3-羟基和3-羧基与柠檬酸配体形成1:2的配合物, 两个端羧基没有参与配位。通过计算稀土离子和柠檬酸配体中各个碳原子间的空间距离的相对比, 建立了稀土离子与柠檬酸配体配位的新模式。