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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.
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
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.
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
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.
Luminescence of Eu3+ ions in hybrid polymer‐inorganic composites based on poly(methyl methacrylate) and zirconia nanoparticles 下载免费PDF全文
Alexander N. Bugrov Anastasia Yu. Zavialova Ruslan Yu. Smyslov Tatyana D. Anan'eva Elena N. Vlasova Maxim V. Mokeev Artem E. Kryukov Gennady P. Kopitsa Vitaliy Pipich 《Luminescence》2018,33(5):837-849
Spherical nanoparticles of ZrO2 with 2 and 10 mol% EuO1.5 up to 20 nm size were prepared by the method of hydrothermal synthesis for luminescent functionalization of the polymer–inorganic nanocomposites based on poly(methyl methacrylate). Surface modification of oxide nanoparticles was carried out by 3‐(trimethoxysilyl)propyl methacrylate, dimethoxymethylvinyl silane and 2‐hydroxyethyl methacrylate to provide uniform distribution and to prevent agglomeration of nanosized filler in the polymer matrix. Polymer–inorganic composites were synthesized by in situ free radical polymerization in bulk. Structuring of ZrO2‐EuO1.5 nanoparticles in the poly(methyl methacrylate) was studied by very‐small‐angle neutron scattering. According to the results, the dependence of photoluminescent properties of ZrO2‐EuO1.5 nanoparticles on the content of lanthanide, the symmetry of the crystal field, surface treatment and the polymer matrix were established. A correlation was shown between Stark splitting in luminescence spectra of ZrO2‐EuO1.5 nanoparticles and their phase composition. Using MMT‐assay it was shown that composites based on poly(methyl methacrylate) and ZrO2‐EuO1.5 nanoparticles do not have cytotoxic properties, which makes it possible to use them as prosthesis materials with contrasted and luminescent imaging properties. 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.
Root DD 《Cell biochemistry and biophysics》2002,37(2):111-139
Actin and myosin interact in a cyclic series of steps linked to the hydrolysis of ATP that are representative of an ancient
and widespread molecular mechanism. Spectroscopic findings are related to the analysis of the actin and myosin structures
and results from kinetics, fibers, single molecules, electron microscopy, genetics, and a variety of other biophysical and
biochemical studies on actin and myosin to provide an overview of the steps in this molecular process. The synthesis of the
key findings from these fields reveals a highly efficient engine that amplifies subtle changes in the active site into unsurpassed
molecular displacements. Recent developments in resonance energy-transfer spectroscopy and X-ray crystallography are enabling
a detailed elucidation of the stages of a large power stroke that concurs with evidences from diverse lines of structural
and kinetic inquiry. A complete image of actin and myosin motility appears to include twists, tilts, steps, and dynamics from
both partners that could be described as a molecular dance. 相似文献
10.
Lanthanide-substituted calcium binding proteins are known to partially orient in high magnetic fields. Orientation provides residual dipolar couplings (rdc's). Two of these systems, Tm3+- and Dy3+-substituted calbindin D9k, dissolved in an external orienting medium (nonionic liquid crystalline phase) provide rdc values which are the sum of those induced by the lanthanides and by the liquid crystalline phase on the native calcium binding protein. This structure-independent check shows the innocence of the orienting medium with respect to the structure of the protein in solution. Furthermore, the simultaneous use of lanthanide substitution and external orienting media provides a further effective tool to control and tune the orientation tensor. 相似文献