Atoms Of Cu Research Articles

Isolation of copper thionein from rat liver

The inducible Cu-binding protein from adult rat liver previously referred to as Cu-chelatin has been purified and shown to be Cu-thionein. The Cu-protein was purified to homogeneity by gel filtration and thiopropyl-Sepharose chromatography. The Cu-thionein exhibited an amino acid composition similar but not identical to that of the two forms of rat liver Cd,Zn-thionein. The polypeptide-chain molecular weight of Cu-thionein was indistinguishable from that of Cd,Zn-thionein. The identification of the Cu-protein as metallothionein was substantiated by the complete immunological cross-reactivity with antisera prepared against purified rat liver Cd,Zn-thionein. Purified Cu-thionein bound 9–11 g atoms of Cu per mole of protein in an electron paramagnetic resonance nondetectable form. The Cu Zn ratio of the protein is about 100. Ion-exchange chromatography resolved the Cu-protein into three polymorphic forms which differed from the polymorphism of Cd,Zn-thionein.

Model calculation of NMR satellite data for iron-group atoms in copper

We report model calculations of NMR satellite data for iron-group impurity atoms in Cu which provide a tractable method for relating the experimentally observed Knight shifts to the structure of the magnetic atoms. This model is based on a three-parameter one-electron screened potential with exchange. For Fe, Mn, and Cr impurities we obtain the positions and widths of Anderson-like scattering resonances and find that the numbers of $d$ electrons are nearly integral and indicate $3{d}^{7}$, $3{d}^{5}$, and $3{d}^{4}$ configurational assignments, respectively. The model gives good agreement with near-neighbor Knight shifts, is consistent with bulk susceptibility and high-temperature resistivity, and in most cases agrees with the axial component of the measured anisotropic Knight shifts. We also relate our results to NMR line-broadening data and near-neighbor quadrupole data. The model is formulated to include the case of impurities without a zero-field magnetic moment and is easily extended to account for trends observed as one moves across the entire iron group.

Multi-centre contributions to the anisotropic hyperfine interactions in the cu(ii) bis(dithiocarbamate) complex. Proton hyperfine couplings

One-, two- and three-centre, first-order contributions to the hyperfine coupling tensors of the central metal atom and of the ligand atoms in Cu(II) bis(N,N-diethyldithiocarbamate) are calculated. Conclusions are drawn on the relative magnitude of the multi-centre and the one-centre contributions The multi-centre contributions are always small and are of importance only if the one-centre contributions are negligible themselves The latter holds especially for the anisotropic coupling tensors of the protons the calculated two- and three-centre contributions agree very well with the experimental values.

Theory Relating NMR Satellite Data to the Structure of Iron-Group Impurities in Copper

We report model calculations of NMR satellite spectra for Cr, Mn, and Fe atoms in Cu which provide, for the first time, a tractable method for relating the experimentally observed Knight shifts to the structure of the magnetic atoms. Based on a three-parameter one-electron screened potential with exchange, the model is also consistent with bulk susceptibility and high-temperature resistivity measurements. We determine the position and widths of the conduction-electron scattering resonances, and the number of $3d$ electrons on the magnetic atoms.

Auger Study of Preferential Sputtering for Cu–Ni Alloy Sample

Preferential sputtering has been studied by in-situ Auger measurement of sputtered Cu–Ni (50 wt.%) sample surface and of sputter-deposited layer on Ta-substrate, and individual sputtering yields of the constituent elements, Cu and Ni, in the alloy have been measured. The results clearly show that the change in the surface concentration of the sputtered sample is described by the preferential sputtering which is caused by the different sputtering yields of the constituent elements. Moreover, it has been experimentally confirmed by measuring the composition of the sputter-deposited layer that the proportion of the sputtered-off atoms of Cu and Ni equals the bulk concentration of the sputtered sample at the equilibrium state. The variation of the surface concentration of the sputtered sample has also been explained from the simple model of Ho et al. with considerable success, and the thickness of the altered layer on the sputtered sample has been estimated to be ∼15 Å under normally incident 500 eV-Ar ion bombardment.

On the local susceptibility of Fe in Cu from Mössbauer experiments

The variation of the local susceptibility of isolated Fe atoms in Cu with temperature is a problem which has resisted agreement among previous workers. We present additional Mössbauer measurements obtained over the range 4.2 to 126 K and in applied fields of 2.4 to 8.4 T. No anomalous behaviour of the local susceptibility is observed.

Temperature Dependence of the Electric Field Gradient in Cubic Ag Metal Doped with Impurities

The electric quadrupole interactions produced by near-neighbor impurity atoms of Cu, Zn, In, Sn, and Au in a cubic Ag metal lattice are measured as a function of temperature by the time-differential perturbed angular correlation method. The obtained electric quadrupole frequencies $\ensuremath{\omega}$ can be reproduced by the relation $\ensuremath{\omega}(T)=\ensuremath{\omega}(0)(1\ensuremath{-}\ensuremath{\alpha}{T}^{\frac{3}{2}})$ with a strong dependence of the coefficient $\ensuremath{\alpha}$ on the impurity atom. The results are discussed in terms of recently proposed models to explain the ${T}^{\frac{3}{2}}$ dependence.

Electric field gradients created by near neighbour impurity atoms in a cubic silver host

The electric quadrupole interactions produced by near neighbour impurity atoms of Cu, Au, Zn, In, Sn and Bi on111Cd probe nuclei in a cubic Ag lattice were studied by the TDPAC method. The effects of the type of impurity and its concentration have been investigated. The results show the presence of a high-frequency interactionvQh superimposed to a smeared out low frequencyvQl. The high frequency interaction, in the range 20 to 600 MHz, is attributed to impurity atoms located in nearest neighbour sites, while the low frequency interaction, in the range 2 to 12 MHz, is generated by impurities distributed at various different atomic distances from the probe nuclei. BothvQh andvQl increase with impurity concentration leaving the ratiovQh/vQl almost constant. The results show that the high frequencyvQh is linearly dependent on the solute valence, and a logarithmic function of the impurity concentration, in the range 0.5 to 4.5 at. %. Large size effects have been observed in CuAg and BiAg alloys. Instead for ZnAg and SnAg, thevQh andvQl variation is attributed basically to charge effects.

Analysis of the recovery of dilute alloys of gold and silver in copper after low temperature electron irradiation

Abstract The influence of dilute concentrations of both Au and Ag atoms on the stage I and stage I1 annealing structure in copper has been investigated using electrical resistivity measurements. An excellent agreement of the stage Id and I, experimental data with the theoretical predictions of the SimpsonJosin full diffusional theory is obtained; this analysis determines the capture radius of solute Au atoms in Cu to be 1.7 ± 0.1 I.c. and that of solute Ag atoms in Cu to be 1.8 ± 0.1 I.c. (in comparison with an interstitial-vacancy capture radius of 3.2 1.c.). Four well-defined recovery substages are observed in the dilute alloys during stage I1 recovery. An interpretation of each of these substages, consistent with experimental results, is presented. The following processes were observed to occur during stage 11: The release of trapped interstitial atoms from trapping centers formed by the proximity of a gold atom near a vacancy; the rearrangement of trapped interstitials to new trapping positions at imp...

A naturally occurring Cu-thionein in Saccharomyces cerevisiae.

A naturally occurring monodisperse Cu-thionein was prepared using ammonium sulfate precipitation followed by ion exchange (DEAE 23) and gel chromatography (Sephadex G-75). The chromatographic steps were repeated at least twice, or until the Cu-thionein remained homogeneous when subjected to analytical polyacrylamide disc electrophoresis. The molecular weight of this copper protein was 9500+/-500. Up to 24.3% cysteine residues were determined, indicating the relationship to the metallothioneins. Aromatic amino acids were virtually absent, while there were about three times as many acidic amino acid residues, including aspartate and glutamate, as in metallothioneins. 10 g atoms of Cu were measured per mole of protein. The copper binding strength of thionein was extremely high. Displacement by protons (pH 1.5) and gel chromatography or dialysis employing EDTA were not effective. Dialysis against diethyldithiocarbamate produced a protein essentially free of copper. Both the ultraviolet properties and the circular dichroism measurements proved identical with those properties reported for artificially prepared Cu-thionein (see ref.[1]. The major absorption was in the far ultraviolet region with a weak shoulder at 270 nm attributable to copper charge-transfer transititions. 6 Cotton extrema were seen at 213, 283 and 302 nm (negative) and 245, 328 and 359 nm (positive). The possible role of Cu-thionein as an electron transport system was discussed.

The effect of plastic deformation on a metastable Cu-1.92wt.% Fe alloy

A Cu-1.92 wt.% Fe alloy was cold-worked and studied by Mössbauer effect spectroscopy. In the asquenched alloy the following metastable phases were detected: γ 0-isolated Fe atoms in Cu, γ( n 2- clusters of n- Fe atoms and a negligible amount of γ 1-precipitates of f.c.c. iron. The alloy deviated strongly from randomness, but became more random after cold-work. A reduction of 87% by rolling, led to a shift in the position of the centroid of the γ 0-line of Δ( I. S.) γ 0 = 0.02 mm s −1, and a broadening of ΔΓ = 0.04 mm s −1. The changes in the Mössbauer parameters, of the γ 0-line have been interpreted as indicating a relief in the compressive stresses imposed upon a Fe atom at a substitutional lattice site in Cu.

Measurements of electron-spin density near Co atoms in Cu

We report nuclear-magnetic-resonance studies of Cu Co in which we resolve and identify satellites due to three shells of Cu near neighbors around isolated Co impurities. The satellite positions show that the spatial form of the spin polarization oscillates with distance and that the conduction electrons on these atoms contribute about ---8% of the total impurity susceptibility. The splittings are measured from 1.5 to 450\ifmmode^\circ\else\textdegree\fi{}K and from 6.4 to 63 kG and compared with the susceptibility $\ensuremath{\chi}$ of singles. The width of the main line is decomposed into contributions ${\ensuremath{\Delta}}_{1}$ and ${\ensuremath{\Delta}}_{2}$ from isolated Co atoms and pairs of Co atoms, respectively, by use of the temperature variation of the splitting and of the pair susceptibility ${\ensuremath{\chi}}_{2}$. the theory of Walstedt and Walker is used to show that ${\ensuremath{\Delta}}_{1}$ agrees with what one would expect from the satellite splittings, and that $\frac{{\ensuremath{\Delta}}_{1}}{{\ensuremath{\Delta}}_{2}}$ is reasonable in terms of the magnitude and temperature dependence of ${\ensuremath{\chi}}_{1}$ and ${\ensuremath{\chi}}_{2}$. The results are scaled to CuFe to show that much of the observed linewidth anomaly is of the same origin, and must be included before possible conclusions can be made about Kondo correlation effects.

A Calculation of the Electronic Structure of an Impurity Atom of Non-Transition Element in Transition Metals –The Nuclear Spin-Lattice Relaxation Time of an Impurity Atom (Al and Cu) in Pd–

Kohzuki and Asayama have shown that the nuclear spin-lattice relaxation time T 1 of Al in Pd 1- x Al x in the range of small x (<0.03) becomes about 10 times as long as that of pure Al and in the case of Pd 1- x Cu x , T 1 of Cu does not change appreciably in the whole range of x . These data are analysed in this paper by carrying out ab initio calculations of the electronic structure of a single impurity atom in Pd. It is shown that T 1 of Al nucleus is determined mainly by the contact interaction with conduction electrons. The increase of T 1 is a direct result of the reduction of the density of electrons with the Fermi energy at the impurity nucleus, ρ s (0, E F ), which arises from the fact that the Fermi level is situated at the valley between the bonding and antibonding states of the s states at the impurity site with the host d band. On the other hand, in the case of an impurity atom of Cu in Pd, the orbital relaxation, which can be neglected in pure Cu, compensates the decrease of the relaxation r...

Measurement of Electron Spin Density near Co Atoms in Cu

We report NMR and double resonance studies of $\mathrm{Cu}\mathrm{Co}$ in which we resolve satellites due to three shells of Cu near neighbors around isolated Co impurities. The satellite positions show that the spatial form of the spin polarization oscillates with distance and that the conduction electrons on these atoms contribute about - 8% of the total impurity susceptibility. The splittings are measured versus temperature from 1.5 to 450 K.

Preparation and physicochemical properties of green pea superoxide dismutase

A procedure is described for preparing purified superoxide dismutase from green peas. The enzyme has no tyrosine and no tryptophan and gives a characteristic ultraviolet spectrum. Like human and bovine enzymes, it contains 2 atoms of Cu and 2 atoms of Zn and the results of sedimentation equilibrium and gel filtration indicate a molecular weight of about 31 500. The spectra of visible absorbance and electron paramagnetic resonance are very similar to those of mammalian superoxide dismutases.

Asymptotic Interaction Energy between Pairs of Point Defects in Cubic Metals

We have calculated the asymptotic interaction energies between pairs of interstitial Cu atoms in Cu and between pairs of vacancies in Al, Na, and K. These calculations were performed using the asymptotic equations of the method of lattice statics. The exact method of lattice statics is based on the Fourier transformation of the direct-space equilibrium equations for a supercell of the lattice containing one defect surrounded by a large number of host atoms. The asymptotic interaction energies were compared with the corresponding results obtained from the exact method of lattice statics. This comparison indicates that elasticity theory cannot be used to obtain strain-field interaction energies for defects nearer than at least 26 or 27 neighbors from each other, and is probably not truly valid until much larger interdefect separations are considered. This result places a heavy restriction on the use of elasticity theory in practical defectinteraction calculations.

Influence of trapping at impurity atoms on diffusion annealing of metals after electron irradiation

Abstract A theory of correlated diffusion annealing is presented which takes into account the trapping of mobile interstitials at impurity atoms. Both the cases of three dimensional diffusion and one dimensional crowdion diffusion are considered. In the case of three dimensional diffusion the trapping can be approximately described by a ‘trapping constant’ in the diffusion equation of the interstitial. To derive this description from the general equations we have used the superposition approximation in which third order correlations are replaced by products of second order correlations. Comparison with experimental data of Sosin and Neely(1) on Au atoms in Cu seems to support the picture of three dimensional diffusion and yields a trapping volume around Au atoms in Cu of about 90 atomic volumes. But from the few data points available no definite conclusions can be drawn concerning the nature of interstitial migration at low temperature.

Structure and properties of hemocyanins: IV. Dissociation of Helix pomatia hemocyanin by succinylation into functional subunits

1. 1.|Hemocyanin of Helix pomatia was succinylated to various degrees with succinic anhydride. Evidence is given that not only the amino groups and the hydroxyl groups of tyrosine, serine and threonine were acylated but also the hydroxyl groups of the carbohydrate moiety of this protein. 2. 2.|Succinylation leads to dissociation of hemocyanin. Even at very low degrees of succinylation dissociation into twentieths (mol. wt. about 500 000) occurred; more exhaustive succinylation did not lead to smaller subunits. 3. 3.|Sedimentation and viscosity measurements, as well as electron microscopy, showed that these succinylated subunits had undergone considerable unfolding. 4. 4.|By progressive succinylation an increasing part of the Cu can be removed by EDTA; the residual Cu remains fully functional. Since 1 molecule of O 2 is bound per 2 atoms of Cu, this is evidence that the Cu atoms of each functional group are labilized simultaneously. 5. 5.|The cooperative interaction between the functional groups which is observed in native hemocyanin is completely lost upon succinylation.

Determination of the unpaired electron density on the central atom of Cu (II) complexes from their EPR spectra in liquid solutions

Determination of the unpaired electron density on the central atom of Cu (II) complexes from their EPR spectra in liquid solutions

Application of the Method of Lattice Statics to Interstitial Cu Atoms in Cu

We have calculated the lattice distortion produced by a body-centered interstitial Cu atom in a Cu host lattice. The calculations have been carried out consistently on the basis of discrete lattice theory, using the technique of lattice statics which is based on the Fourier transformation of the direct-space equilibrium equations. The force constants for the perfect lattice have been taken from measured phonon-dispersion curves, and we have used Huntington's Born-Mayer potential to describe the interaction between the interstitial atom and the atoms of the host lattice. The comparison of our results with those obtained by earlier workers, using semidiscrete matching techniques in which a continuum displacement solution is matched to the displacements of a few close neighbors of the defect, indicates that this latter technique is very unreliable. Similarly, the activation volumes estimated by semidiscrete techniques are also unreliable. We have also used the technique of lattice statics to calculate the strain-field interaction between two body-centered interstitial Cu atoms as a function of their separation. As in the case of the displacement fields, we have made these calculations for two different models which differ in the input elastic constants. For what we believe to be the most realistic of our models, we find a repulsive energy of 0.40 eV for two nearest-neighbor interstitials and a repulsive interaction of 0.0975 eV between two second-neighbor interstitials. For the same model, the calculated formation volume per interstitial is 1.12 atomic volumes.