排序方式: 共有23条查询结果,搜索用时 15 毫秒
1.
Gay GL Lindhout DA Sykes BD 《Protein science : a publication of the Protein Society》2004,13(3):640-651
The potential for using paramagnetic lanthanide ions to partially align troponin C in solution as a tool for the structure determination of bound troponin I peptides has been investigated. A prerequisite for these studies is an understanding of the order of lanthanide ion occupancy in the metal binding sites of the protein. Two-dimensional [(1)H, (15)N] HSQC NMR spectroscopy has been used to examine the binding order of Ce(3+), Tb(3+), and Yb(3+) to both apo- and holo-forms of human cardiac troponin C (cTnC) and of Ce(3+) to holo-chicken skeletal troponin C (sTnC). The disappearance of cross-peak resonances in the HSQC spectrum was used to determine the order of occupation of the binding sites in both cTnC and sTnC by each lanthanide. For the lanthanides tested, the binding order follows that of the net charge of the binding site residues from most to least negative; the N-domain calcium binding sites are the first to be filled followed by the C-domain sites. Given this binding order for lanthanide ions, it was demonstrated that it is possible to create a cTnC species with one lanthanide in the N-domain site and two Ca(2+) ions in the C-domain binding sites. By using the species cTnC.Yb(3+).2 Ca(2+) it was possible to confer partial alignment on a bound human cardiac troponin I (cTnI) peptide. Residual dipolar couplings (RDCs) were measured for the resonances in the bound (15)N-labeled cTnI(129-148) by using two-dimensional [(1)H, (15)N] inphase antiphase (IPAP) NMR spectroscopy. 相似文献
2.
Paramagnetic metal ions in proteins provide a rich source of structural information, but the resonance assignments required
to extract the information can be challenging. Here we demonstrate that paramagnetically shifted 15N-HSQC cross-peaks can be assigned using NZ-exchange spectroscopy under conditions in which the paramagnetic form of the protein is in dynamic equilibrium with its diamagnetic
form. Even slow exchange of specifically bound metal ions may be detected within the long lifetime of 15N longitudinal magnetization of large proteins at high magnetic fields. Alternatively, the exchange can be accelerated using
an excess of metal ions. In the resulting exchange spectra, paramagnetic 15N resonances become visible for residues that are not directly observed in a conventional 15N-HSQC spectrum due to paramagnetic 1HN broadening. The experiments are illustrated by the 30 kDa lanthanide-binding ɛ186/θ complex of DNA polymerase III in the
presence of sub-stoichiometric amounts of Dy3+ or a mixture of Dy3+ and La3+. 相似文献
3.
Valery Andrushchenko Daniele Padula Elena Zhivotova Shigeki Yamamoto Petr Bouř 《Chirality》2014,26(10):655-662
Lanthanide complexes exhibit interesting spectroscopic properties yielding many applications as imaging probes, natural chirality amplifiers, and therapeutic agents. However, many properties are not fully understood yet. Therefore, we applied magnetic circular dichroism (MCD) spectroscopy, which provides enhanced information about the underlying electronic structure to a series of lanthanide compounds. The metals in the M3+ state included Y, La, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu; the spectra were collected for selected tetraphenylporphin (TPP) and octaethylporphin (OEP) complexes in chloroform. While the MCD and UV‐VIS absorption spectra were dominated by the porphyrin signal, metal binding significantly modulated them. MCD spectroscopy was found to be better suited to discriminate between various species than absorption spectroscopy alone. The main features and trends in the lanthanide series observed in MCD and absorption spectra of the complexes could be interpreted at the Density Functional Theory (DFT) level, with effective core potentials on metal nuclei. The sum over state (SOS) method was used for simulation of the MCD intensities. The combination of the spectroscopy and quantum‐chemical computations is important for understanding the interactions of the metals with the organic compounds. Chirality 26:655–662, 2014. © 2014 Wiley Periodicals, Inc. 相似文献
4.
The neutral Schiff base N,N'-bis(pyridoxylideneiminato)ethylene {H(2)pyr(2)en} reacts with Th(NO(3))4.4H2O, NdCl3.6H2O and EuCl3.6H2O to give [Th(pyr(2)en)2(H2O)] (1), [Nd(pyr(2)en)(Hpyr(2)en)].12H2O (2) and [Eu(pyr(2)en)(Hpyr(2)en)] (3). In the three not yet reported bimolecular chelate systems the endo hydroxyl groups of the rings undergo deprotonation confirming the remarkable ability of the pyridoxal-containing ligand H(2)pyr(2)en to yield stable heavy metal chelates with unusual coordination polyhedra. Complexes 2 and 3 show a coordination number 8 for Nd and Eu, achieving a distorted quadratic antiprism. In complex 1 the additional water molecule increases the coordination number of Th to 9 producing a capped square antiprism. The synthesis and structural elucidation of the title complexes starting from a probably non-toxic metabolite like H(2)pyr(2)en should represent a useful contribution to the research on models of prevention and therapy of damage caused by radioactive and heavy elements. 相似文献
5.
Saiki Mitiko Saldiva Paulo H. N. Alice Sérgio Haertel 《Biological trace element research》1999,(1):291-297
In this study, instrumental neutron activation analysis was applied to the determination of Sc, La, Ce, Nd, Sm, Eu, Tb, Yb,
Lu, Hf, Th, and U in lung samples from miners working in coal mines located in the state of Santa Catarina, Brazil. These
results were compared to those from a control group constituted of healthy individuals. The results showed that the elements
determined exhibit considerable intersubject variability within a single group of individuals and the mean values of concentrations
in miners’ lungs were higher than those of normal individuals. Lung samples presented U concentrations varying from 11 to
890 Μg/kg. Therefore, for some samples, the contribution of the uranium fission products in the analysis of La, Ce, Nd, and
Sm was considered by determining the interference correction factors. The accuracy of the results was evaluated by analyzing
certified reference materials. 相似文献
6.
GABA receptor-channel complex as a target site of Mercury,copper, zinc,and lanthanides 总被引:2,自引:0,他引:2
Toshio Narahashi Jenny Yan Ma Osamu Arakawa Eitan Reuveny Masanobu Nakahiro 《Cellular and molecular neurobiology》1994,14(6):599-621
Summary 1. The GABAA receptor-chloride channel complex has been shown to be modulated by a variety of chemicals. Scores of chemicals with diverse and unrelated structures augment the GABA-induced chloride current, while some other chemicals suppress the current. Certain heavy metals and a variety of polyvalent cations increase or decrease the current in a potent and efficacious manner.2. We have studied the mechanisms whereby mercury, copper, zinc, and lanthanides modulate the GABA system by whole-cell and single-channel patch clamp techniques as applied to the rat dorsal root ganglion neurons in primary culture.3. Mercuric chloride augmented the GABA-induced current to 115% of control at 0.1 µM and to 270% of control at 100 µM. It also generated a slowly developing inward current carried by a variety of ions. In contrast, methylmercury suppressed the GABA-induced current. The potent stimulation of the GABA system by mercuric chloride is deemed important in mercury intoxication.4. Copper and zinc suppressed the GABA-induced current with an EC50 of 16 and 19 µM, respectively. They bound to a common site on the external surface of the GABA receptor-channel complex.5. Lanthanum augmented the GABA-induced current with an EC50 of 230 µM by increasing the affinity of the receptor for GABA. It bound to a site on or near the external surface of the GABA receptor-channel complex which is different from the sites for GABA, barbiturates, benzodiazepines, picrotoxin, and copper/zinc.6. Six other lanthanides with larger atomic numbers also exerted the same stimulatory effect with their efficacies increasing with the atomic number.7. Single-channel analyses have revealed that the augmentation of whole-cell current by terbium, a lanthanide, is due to three actions: an increase in the overall mean open time, a decrease in the overall mean closed time, and an increase in the overall mean burst time. 相似文献
7.
Mikhail N. Bochkarev Georgy V. Khoroshenkov Dmitry M. Kuzyaev Anatoly A. Fagin Mikhail E. Burin Georgy K. Fukin Eugeny V. Baranov Alexander A. Maleev 《Inorganica chimica acta》2006,359(10):3315-3320
It was found that the lanthanide diiodides LnI2 (1) (Ln = Nd, Sm, Eu, Dy, Tm, Yb) are dissolved in isopropylamine (IPA) without redox transformations. Stability of the formed solutions decreases in a row Eu ≈ Yb > Sm > Tm > Dy > Nd. Removing of a solvent in vacuum leaves complexes LnI2(IPA)x (2) (Nd, x = 5; Sm, Eu, Dy, Tm, Yb, x = 4) as crystalline colored solids. Stability of 2-Nd,Dy,Tm is higher than that of known THF or DME coordinated salts. Divalent state of metal in the products is confirmed by data of UV-Vis spectroscopy, magnetic measurements and their chemical behavior. Structure of 2-Eu and 2-Tm was established by X-ray diffraction analysis. Oxidation of 2-Nd,Dy in IPA affords amine-amides (PriNH)Ln(IPA)y (3) (Nd, y = 4; Dy, x = 3). n-Propylamine also dissolves the iodides 1-Sm,Eu,Dy,Tm,Yb but stability of the solutions is significantly lower. 1-Nd vigorously reacts with PrnNH2 even at −30 °C which hampers the formation of the solution. 相似文献
8.
Lanthanide ions (Ln(3+)), which have ionic radii similar to those of Ca(2+), can displace the latter in a calcium binding protein, without affecting its tertiary structure. The paramagnetic Ln(3+) possesses large anisotropic magnetic susceptibilities and produce pseudocontact shifts (PCSs), which have r(-3) dependence. The PCS can be seen for spins as far as 45 A from the paramagnetic ion. They aid in structure refinement of proteins by providing long-range distance constraints. Besides, they can be used to determine the interdomain orientation in multidomain proteins. This is particularly important in the context of a calcium binding protein from Entamoeba histolytica (EhCaBP), which consists of two globular domains connected by a flexible linker region containing 8 residues. As a first step to obtain the interdomain orientation in EhCaBP, a suite of 2D and 3D heteronuclear experiments were recorded on EhCaBP by displacing calcium with Ce(3+), Ho(3+), Er(3+), Tm(3+), Dy(3+), and Yb(3+) ions in separate experiments, and the PCS of (1)H(N) and (15)N spins were measured. Such data have been used in the refinement of the individual domain structures of the protein in parallel with the calculation of the respective magnetic anisotropy tensorial values, which differ substantially (2.1-2.8 times) from what is found in other Ca(2+) binding loops. This study provides a structural basis for such variations in the magnetic anisotropy tensorial values. 相似文献
9.
Gelson Manzoni de Oliveira Manfredo Hörner Aline Machado Jorge H.S.K. Monteiro 《Inorganica chimica acta》2011,366(1):203-859
Deprotonated 3-(4-nitrophenyl)-1-phenyltriazene N-oxide reacts with YCl3·6H2O and LnCl3·6H2O (Ln = Eu, Ho, Yb) to give the monoclinic chelate complexes [Y{O2N(C6H4)NNN(O)Ph}4](Et3NH)·H2O (1) (Ph = C6H5; Et = C2H5) and [LnIII{O2N(C6H4)NNN(O)Ph}4](Et3NH)·H2O·{CH3OH∗} {LnIII = Eu (2), Ho (3), Yb∗ (4), in which the metal centers present a square antiprismatic configuration. As already observed for hydrated ammonium complexes of triazene-oxides ligands with (C6H4)−NO2 groups, multiple, effective O···H and N···H interactions hold the species in supramolecular 3D assemblies. The optical and the luminescent properties of the triazene-oxide europium complex 2 are also presented and fully discussed. 相似文献
10.
Lanthanide (III) luminescence is very characteristic: it is characterized by narrow emission bands, large Stokes shift, and a long excited state lifetime. Moreover, chiral lanthanide complexes can emit strongly circularly polarized light in a way that is almost precluded to purely organic molecules. Thanks to the sensitivity and specificity of the Ln circularly polarized luminescence (CPL) signal, CPL‐active complexes are therefore employed as bioanalytical tools and other uses can be envisaged in many other fields. Here we present a brief overview of the most recently developed CPL‐active lanthanide complexes and a selected few examples of their applications. We briefly discuss the main mechanisms that can rationalize the observed outstanding CPL properties of these systems, and some practical suggestions on how to measure and report data. Chirality 27:1–13, 2015. © 2014 Wiley Periodicals, Inc. 相似文献