bluuebunny/crossref_metadata_2025 huggingface dataset:
CD24 expression is a significant predictor of PSA relapse and poor prognosis in low grade or organ confined prostate cancer
Authors: Kristiansen Glen , Pilarsky Christian , Pervan Janja , Stürzebecher Burkhard , Stephan Carsten , Jung Klaus , Loening Stefan , Rosenthal Andre , Dietel Manfred
Published: January 2004

BACKGROUND

The prognostic impact of tumor grading and staging is markedly reduced in organ confined or moderately differentiated prostate cancer, which underscores the importance of new prognostic markers. Evaluating public expression data of prostate cancer, we found an upregulation of the candidate gene CD24.

METHODS

We examined immunohistochemically the expression of CD24 protein in 31 nodal metastases and 102 adenocarcinomas of the prostate and correlated our findings to clinicopathological parameters.

RESULTS

CD24 expression was found in 48% of primary prostate cancer cases and in 68% of lymph node metastases. Kaplan Meier curves and Cox regression analysis showed that CD24 expression was strongly linked to significantly earlier disease progression (relative risk = 3.2), which was especially pronounced in organ confined, or moderately differentiated primary prostate tumors.

CONCLUSIONS

We conclude that CD24 is an important prognostic tissue marker for prostate cancer which could help to define patients of low or high risk of recurrence. © 2003 Wiley‐Liss, Inc.
Dutasteride, the dual 5α–reductase inhibitor, inhibits androgen action and promotes cell death in the LNCaP prostate cancer cell line
Authors: Lazier C.B. , Thomas L.N. , Douglas R.C. , Vessey J.P. , Rittmaster R.S.
Published: January 2004

BACKGROUND

Reduction of T to DHT by 5αR in the prostate enhances androgenic activity for most targets. Inhibition of 5αR activity with finasteride attenuates androgen action in men and animal models. The objective of this study was to compare and contrast the effects of a potent new 5αR inhibitor, dutasteride, with finasteride in the LNCaP prostate cancer cell line.

METHODS

LNCaP cells were incubated for varying times with T or DHT in steroid‐free medium in the absence or presence of increasing doses of dutasteride or finasteride and the effects on 5αR activity, PSA accumulation in the medium, and on cell proliferation were determined. Drug effects on apoptosis were investigated using Annexin V staining and a cell death ELISA assay. Effects of the drugs on AR ligand‐binding activity and on AR protein levels were determined.

RESULTS

Dutasteride inhibited 3H‐T conversion to 3H‐DHT and, as anticipated, inhibited T‐induced secretion of PSA and proliferation. However the drug also inhibited DHT‐induced PSA secretion and cell proliferation (IC50 ∼ 1 μM). Finasteride also inhibited DHT action but was less potent than dutasteride. Dutasteride competed for binding the LNCaP cell AR with an IC50 ∼ 1.5 μM. High concentrations of dutasteride (10–50 μM), but not finasteride, in steroid‐free medium, resulted in enhanced cell death, possibly by apoptosis. This was accompanied by loss of AR protein and decreased AR ligand‐binding activity. Occupation of AR by R1881 partly protected against cell death and loss of AR protein. PC‐3 prostate cancer cells, which do not contain AR, also were killed by high concentrations of dutasteride, as well as by 50 μM finasteride.

CONCLUSIONS

Dutasteride exhibited some inhibitory actions in LNCaP cells possibly related to 5αR inhibition but also had antiandrogenic effects at relatively low concentrations and cell death‐promoting effects at higher concentrations. Finasteride also was antiandrogenic, but less than dutasteride. The antiandrogenic effects may be mediated by the mutant LNCaP cell AR. Promotion of cell death by dutasteride can be blocked, but only in part, by androgens. © 2003 Wiley‐Liss, Inc.
Molecular basis for redox‐Bohr and cooperative effects in cytochrome c3 from Desulfovibrio desulfuricans ATCC 27774: Crystallographic and modeling studies of oxidized and reduced high‐resolution structures at pH 7.6
Authors: Bento Isabel , Matias Pedro M. , Baptista António M. , da Costa Patricia N. , van Dongen Walter M.A.M. , Saraiva Lígia M. , Schneider Thomas R. , Soares Cláudio M. , Carrondo Maria A.
Published: December 2003

The tetraheme cytochrome c3 is a small metalloprotein with ca. 13,000 Da found in sulfate‐reducing bacteria, which is believed to act as a partner of hydrogenase. The three‐dimensional structure of the oxidized and reduced forms of cytochrome c3 from Desulfovibrio desulfuricans ATCC 27774 at pH 7.6 were determined using high‐resolution X‐ray crystallography and were compared with the previously determined oxidized form at pH 4.0. Theoretical calculations were performed with both structures, using continuum electrostatic calculations and Monte Carlo sampling of protonation and redox states, in order to understand the molecular basis of the redox‐Bohr and cooperativity effects related to the coupled transfer of electrons and protons. We were able to identify groups that showed redox‐linked conformational changes. In particular, Glu61, His76, and propionate D of heme II showed important contributions to the redox‐cooperativity, whereas His76, propionate A of heme I, and propionate D of heme IV were the key residues for the redox‐Bohr effect. Upon reduction, an important movement of the backbone region surrounding hemes I and II was also identified, that, together with a few redox‐linked conformational changes in side‐chain residues, results in a significant decrease in the solvent accessibility of hemes I and II. Proteins 2004. © 2003 Wiley‐Liss, Inc.
Enriching the sequence substitution matrix by structural information
Authors: Teodorescu Octavian , Galor Tamara , Pillardy Jaroslaw , Elber Ron
Published: December 2003

A fundamental step in homology modeling is the comparison of two protein sequences: a probe sequence with an unknown structure and function and a template sequence for which the structure and function are known. The detection of protein similarities relies on a substitution matrix that scores the proximity of the aligned amino acids. Sequence‐to‐sequence alignments use symmetric substitution matrices, whereas the threading protocols use asymmetric matrices, testing the fitness of the probe sequence into the structure of the template protein. We propose a linear combination of threading and sequence‐alignment scoring function, to produce a single (mixed) scoring table. By fitting a single parameter (which is the relative contribution of the BLOSUM 50 matrix and the threading energy table of THOM2) we obtain a significant increase in prediction capacity in the twilight zone of homology modeling (detecting sequences with <25% sequence identity and with very similar structures). For a difficult test of 176 homologous pairs, with no signal of sequence similarity, the mixed model makes it possible to detect between 40 and 100% more protein pairs than the number of pairs that are detected by pure threading. Surprisingly, the linear combination of the two models is performing better than threading and than sequence alignment when the percentage of sequence identity is low. We finally suggest that further enrichment of substitution matrices, combing more structural descriptors such as exposed surface area, or secondary structure is expected to enhance the signal as well. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Docking studies and model development of tea polyphenol proteasome inhibitors: Applications to rational drug design
Authors: Smith David M. , Daniel Kenyon G. , Wang Zhigang , Guida Wayne C. , Chan Tak‐Hang , Dou Q. Ping
Published: December 2003

Previously, we demonstrated that natural and synthetic ester bond‐containing green tea polyphenols were potent and specific non‐peptide proteasome inhibitors. However, the molecular mechanism of inhibition is currently unknown. Here, we report that inhibition of the chymotrypsin activity of the 20S proteasome by (−)‐epigallocatechin‐3‐gallate (EGCG) is time‐dependent and irreversible, implicating acylation of the β5‐subunit's catalytic N‐terminal threonine (Thr 1). This knowledge is used, along with in silico docking experiments, to aid in the understanding of binding and inhibition. On the basis of these docking experiments, we propose that (−)‐EGCG binds the chymotrypsin site in an orientation and conformation that is suitable for a nucleophilic attack by Thr 1. Consistently, the distance from the electrophilic carbonyl carbon of (−)‐EGCG to the hydroxyl group of Thr 1 was measured as 3.18 Å. Furthermore, the A ring of (−)‐EGCG acts as a tyrosine mimic, binding to the hydrophobic S1 pocket of the β5‐subunit. In the process, the (−)‐EGCG scissile bond may become strained, which could lower the activation energy for attack by the hydroxyl group of Thr 1. This model is validated by comparison of predicted and actual activities of several EGCG analogs, either naturally occurring, previously synthesized, or rationally synthesized. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Improved thermostability of bacillus circulans cyclodextrin glycosyltransferase by the introduction of a salt bridge
Authors: Leemhuis Hans , Rozeboom Henriëtte J. , Dijkstra Bauke W. , Dijkhuizen Lubbert
Published: December 2003

Cyclodextrin glycosyltransferase (CGTase) catalyzes the formation of cyclodextrins from starch. Among the CGTases with known three‐dimensional structure, Thermoanaerobacterium thermosulfurigenes CGTase has the highest thermostability. By replacing amino acid residues in the B‐domain of Bacillus circulans CGTase with those from T. thermosulfurigenes CGTase, we identified a B. circulans CGTase mutant (with N188D and K192R mutations), with a strongly increased activity half‐life at 60°C. Asp188 and Arg192 form a salt bridge in T. thermosulfurigenes CGTase. Structural analysis of the B. circulans CGTase mutant revealed that this salt bridge is also formed in the mutant. Thus, the activity half‐life of this enzyme can be enhanced by rational protein engineering. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Lipoxygenase interactions with natural flavonoid, quercetin, reveal a complex with protocatechuic acid in its X‐ray structure at 2.1 Å resolution
Authors: Borbulevych Oleg Y. , Jankun Jerzy , Selman Steven H. , Skrzypczak‐Jankun Ewa
Published: December 2003

PUFA metabolites have a profound effect on inflammatory diseases and cancer progression. Blocking their production by inhibiting PUFA metabolizing enzymes (dioxygenases: cyclooxygenases and LOXs) might be a successful way to control and relieve such problems, if we learn to better understand their actions at a molecular level. Compounds with strong antioxidative and free radical scavenging properties, such as polyphenols, could be effective in blocking PUFA activities, and natural flavonoids possess such qualities. Quercetin belongs to the group of natural catecholic compounds and is known as a potent, competitive inhibitor of LOX. Structural analysis reveals that quercetin entrapped within LOX undergoes degradation, and the resulting compound has been identified by X‐ray analysis as protocatechuic acid (3,4‐dihydroxybenzoic acid) positioned near the iron site. Its C3‐OH group points toward His523, C4‐OH forms a hydrogen bond with OC from the enzyme's C‐terminus, and the carboxylic group is incorporated into the hydrogen bonding network of the active‐site neighborhood via Gln514. This unexpected result, together with our previous observations concerning other polyphenols, yields new evidence about the metabolism of natural flavonoids. These compounds might be vulnerable to the co‐oxidase activity of LOX, leading to enzyme‐stimulated oxidative degradation, which results in an inhibitor of a lower molecular weight. Proteins 2004;54:000–000. © 2003 Wiley‐Liss, Inc.
Structural and electronic properties of defect and intramolecular junctions for single‐walled carbon nanotube
Authors: Liu Hong , Chen Jiangwei , Yang Huatong
Published: December 2003

The influences of different distributions of defects in (5, 5) single‐walled carbon nanotube (SWCNT) on the electronic structure of SWCNT are considered. Furthermore, we suggest one way to connect two perfect semi‐infinite tubes with different chiralities, such as four different (5, 5)/(n, 0) (n = 8, 9, 10) intramolecular junctions. Their electronic local density of states (LDOS) and quantum conductance are studied. It is found that the conductance gap of the metal/semiconductor heterojunction is not determined only by the electronic structure of semiconductor tube, and the defect distribution mainly change the step behavior of conductance, which is particularly obvious in (5, 5)/(9, 0) metal/metal junctions. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐pressure stability and structural properties of CdS and CdSe
Authors: Benkhettou N. , Rached D. , Soudini B. , Driz M.
Published: December 2003

The structural phase transformations of CdS and CdSe under high pressure are studied by using the local approximation to the density functional theory, and the one‐electron equations are solved by means of the full‐potential linear muffin‐tin‐orbital method FP‐LMTO. CdS and CdSe are found to have nearly similar structural systematics under high pressure. In CdS, the Pmmn phase is predicted after the rocksalt structure, and in CdSe the Cmcm structure is thermodynamically stable after the rocksalt structure. We also find a thermodynamic stability range for the CsCl phase of CdSe. The structural properties of the zincblende, wurtzite, rocksalt, Pmmn, and Cmcm phases are presented. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The proton diffusivity of amorphous tantalum oxide thin films
Authors: Yu G. T.
Published: December 2003

Proton diffusion in tantalum oxide thin film is of significant interest because of its importance in barrier, sensor, and catalytic‐coating applications. In this study, a novel method based on potential‐pH response measurement was used to determine proton diffusivity of amorphous tantalum oxide thin films. This technique is based on the model of diffusion‐controlled proton transport in the oxide surface, measures the potential‐pH response in a thermostatic measurement set‐up. The proton diffusivity of amorphous tantalum oxide films obtained from this method was 4 × 10–21 cm2/s. The novel method is a relatively simple experimental procedure, which eliminates complications arising from surface‐related effects and/or the presence of hydrogen traps in the metal such as those found in the conventional permeation method. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of the behaviour of magnitude m with magnetic field in corrective term “mT1/2”of the metallic electrical conductivity in n‐type InP
Authors: El kaaouachi A. , Nafidi A. , Biskupski G.
Published: December 2003

We present measurements of the electrical conductivity of barely metallic n‐type indium phosphide (InP) that are driven to the metal‐insulator transition (MIT) by a magnetic field. The experiments are carried out at low temperature in the range 4.2−0.066 K and in magnetic fields up to 11 T. The analysis of the low‐temperature correction to the Boltzmann conductivity due to electron–electron interaction as a function of the magnetic field allowed us to study the influence of exchange and Hartree interactions on the change of the sign of the electron–electron interaction correction. When the magnetic field is increased, several phenomena contribute to this corrective term “mT1/2” among which are the spin‐splitting effect, the electron–electron interaction effect, and weak localisation effect. Not too close to the MIT, both the inelastic diffusion length LI and the interaction length LT contribute to a T1/2 corrective term of the metallic electrical conductivity σ. It is convenient to develop a criterion to distinguish their contribution. This is based on the relation between the magnitude m and the zero temperature σ (T = 0). (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Four‐sublattice ferrimagnetic systems: I. Quantum fluctuations of spins at zero temperature
Authors: Qiu Rong‐ke , Zhang Zhi‐dong
Published: December 2003

Within the framework of the linear spin wave approximation, the quantum fluctuations of spins at zero temperature in four‐sublattice ferrimagnetic systems are studied by employing retard Green's functions. The effects of exchange constants on the quantum fluctuations of spins are discussed for three different spin‐configurations. The magnetic properties of these spin configurations are related to their magnetically structural symmetry. When the parameters of the exchange couplings are adjusted, the crossover of the spin configurations results in the strong quantum fluctuations, owing to the behaviors of the non‐three‐dimensional magnetically system. When two of the four exchange‐constants in the present four‐sublattice bulk systems are set to be zero, the system behaves as a non‐three‐dimensionally magnetic system, although the structure of the system is still three‐dimensional. All the exchange couplings involve in the quantum competition of the systems, but the effects of antiferromagnetic and ferromagnetic exchange couplings are different evidently. The antiferromagnetic exchange couplings play an important role in a balance of the quantum competition. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Four‐sublattice ferrimagnetic systems: II. Effects of the spin quantum number
Authors: Qiu Rong‐ke , Zhang Zhi‐dong
Published: December 2003

The effects of the spin quantum number of each sublattice on the quantum fluctuations are discussed for different spin configurations in four‐sublattice ferrimagnetic systems. In multi‐sublattice ferrimagnets, although the individual sublattice magnetization vectors do not offset each other, but their deviations vectors can cancel out. Namely, the sum of the deviations of magnetization of sites with same initiate spin direction, equals to that of sites with opposite initiate spin direction Σi Δ = Σj Δ, i and j denote respectively the spins along the up and down initiate spin directions). The role of the spin quantum number of each site on magnetic properties of the system is correlative with properties of the exchange couplings surrounding the site. The results show that the proportion of ferromagnetic and antiferromagnetic exchange couplings, the spin quantum number of each sublattice and the magnetically structural symmetry of the system all play important roles on the quantum fluctuations of the systems. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Field‐induced carrier redistribution in double‐quantum‐well superlattices
Authors: Kleinert P. , Bryksin V. V.
Published: December 2003

The field‐induced carrier redistribution in double‐quantum‐well superlattices is treated on the basis of the density‐matrix approach. The Hamiltonian of the three‐level system is simplified by a canonical transformation. Two different types of the field‐mediated carrier redistribution are identified, which refer to intra‐cell and inter‐cell transitions. On the one hand, the occupation numbers of the three levels cross each other, when the levels of different wells of a given superlattice cell are aligned due to the electric field. These intra‐cell transitions lead to a formal population inversion. On the other hand, there is a redistribution of carriers mediated by inter‐cell transitions giving rise to a tunneling resonance characterized by extrema in the distribution function. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comment on “Tunable spin‐injection and magnetoconductance in a novel 2DEG‐ferromagnet structure” [phys. stat. sol. (b) 235, No. 1, 157–161 (2003)]
Authors: Papp G. , Peeters F. M.
Published: December 2003

We point out that the predicted strong spin‐injection effect by Jiang and Jalil [phys. stat. sol. (b) 235, 157 (2003)] for a double magnetic barrier structure is based on a wrong calculation of the transmission probability. We corrected the result and found no significant spin‐injection. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
‘Tunable spin‐injection and magnetoconductance in a novel 2DEG‐ferromagnet structure’” [phys. stat. sol. (b) 241, No. 1, 222 (2004)]
Authors: Jiang Y. , Jalil M. B. A.
Published: December 2003

In this reply, we agree with the comments from Papp et al. that a symmetric (S) double barrier induces only a weak spin‐polarization (P). But the main objective of us was to propose a practical arrangement to achieve a symmetric double barrier because P vanishes for any antisymmetric configuration. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase transitions detection by means of a contact electrode
Authors: Matlak M. , Pietruszka M.
Published: December 2003

We investigate theoretically and next experimentally a new possibility to detect critical temperatures of solids by means of a very simple electrical circuit consisting of an analyzed sample (exhibiting phase transitions) and a contact electrode (hereafter reference electrode) where the constant voltage is applied only to the latter one. The measured system is placed into a thermostat and the electric current flow through the reference electrode is measured as function of temperature. By assuming a model Hamiltonian for the probed sample describing ferromagnetic, superconducting or reentrant phase transitions and a one‐band model for the contact electrode we calculate d.c. conductivity of the reference electrode. The temperature dependence of the conductivity of this electrode clearly indicates (in the form of kinks) the transition temperatures connected with phase transitions occurring in the investigated material. This is due to the fact that the chemical potential of the whole system in contact should equal at equilibrium. Our considerations suggest straightforward application of such a circuit in a direct laboratory praxis, especially because (beyond simplicity) the applied method possesses unlimited temperature range and can be considered as noninvasive with respect to the investigated sample. To verify the effect experimentally we have used as an investigated sample an antiferromagnetic Cr material and Cu as the reference electrode. The measurements of the resistivity R(Cr + Cu) and R(Cu) alone as functions of temperature made a possibility to plot the difference R(Cr + Cu) − R(Cu) vs temperature. This plot enabled to identify the critical Neel temperature of the Cr sample corresponding to the profound minimum in this curve. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
IUPAP Workshop on Scientific Misconduct and the Role of Physics Journals in its Investigation and Prevention, London, UK, 13–14 October 2003
Authors: Hildebrandt Stefan
Published: December 2003

Conference Reports are meant to offer an authoritative view on a recently held scientific meeting rather than a comprehensive list of the conference presentations. Authors are invited to describe what they feel were the most interesting contributions.

Changing the culture of science and publication was the tenor at the IUPAP Workshop on Scientific Misconduct and the Role of Physics Journals in its Investigation and Prevention, recently held in London. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge transfer and charge transport on the double helix
Authors: Armitage N. P. , Briman M. , Grüner G.
Published: December 2003

We present a short review of various experiments that measure charge transfer and charge transport in DNA. Some general comments are made on the possible connection between various ‘chemistry‐style’ charge transfer experiments that probe fluorescence quenching and remote oxidative damage and ‘physics‐style’ measurements that measure transport properties as defined typically in the solid‐state. We then describe measurements performed by our group on the millimeter wave response of DNA. By measuring over a wide range of humidity conditions and comparing the response of single strand DNA and double strand DNA, we show that the appreciable AC conductivity of DNA is not due to photon assisted hopping between localized states, but instead due to dissipation from dipole motion in the surrounding water helix. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relaxation of non‐equilibrium charge carriers in the hopping regime
Authors: Bleibaum O. , Haba E. , Böttger H. , Bryksin V. V.
Published: December 2003

We discuss a kinetic model for glass‐like relaxation processes in a strongly localized electron system. In our hopping model we assume that the charge carriers can exchange maximally an amount ω of energy in one hop. The investigation of the system shows that the energy scale ω discriminates between two different relaxation modes. If the thermal energy is large compared to ω the relaxation is percolation like. In this regime the relaxation is determined by the same paths as the close‐to‐equilibrium conductivity in a transport problem. If the thermal energy is small compared to ω then the relaxation becomes Miller‐Abraham like. In this relaxation mode the charge carriers always jump to the next closest site. The differences between these transport regimes manifest themselves in the typical time scales governing the relaxation and in the structure of the transport coefficients. To discuss them we focus on energy relaxation processes. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Long‐time relaxation of conductivity in hopping regime
Authors: Efros A. L. , Tsigankov D. N. , Pazy E. , Laikhtman B. D.
Published: December 2003

Using numerical simulations we studied the long‐time relaxation of the hopping conductivity. We perturbed the system through insertion of electrons and monitored the conductivity as a function of time. Even though employing numerical simulations one can only follow the system for very short time scales we have shown that during such available times we can reach an apparent saturation of conductivity and energy. In order to investigate the long‐time relaxation of the system we studied the difference between the saturated values of the conductivities obtained by the short‐time relaxation from initial excited states with different electron distribution. We have related these two typical time scales to relaxation in one pseudoground state and to very slow transitions between pseudoground states. By employing two different two‐dimensional models with electron–electron interactions we were able to show the effect of disorder on the relaxation of conductivity. In the strong‐disorder case the universality of the Coulomb gap, which is responsible for the universal Efros–Shklovskii law for the conductivity, suppresses the long‐time relaxation of conductivity since the universality strongly decreases the dispersion of conductivities of the pseudoground states. In the second model with a weak external disorder we found a difference between saturated values of conductivity in agreement with the experimental data. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wigner approach to quantum dynamics simulations of the interacting carriers in disordered systems
Authors: Filinov V. , Thomas P. , Bonitz M. , Fortov V. , Varga I. , Meier T.
Published: December 2003

The new method for solving Wigner–Liouville's type equations and studying dynamics of quantum particles has been developed within the Wigner formulation of quantum statistical mechanics. This approach combines both molecular dynamics and Monte Carlo methods and computes traces and spectra of the relevant dynamical quantities. Considering, as an application, the quantum dynamics of an ensemble of interacting electrons in an array of random scatterers clearly demonstrates that the many‐particle interaction between the electrons can lead to an enhancement of the electrical conductivity. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the mechanism of superionic conduction in the zero‐dimensional hydrogen‐bonded crystals M3H(XO4)2 with M = K, Rb, Cs and X = S, Se
Authors: Kamimura Hiroshi , Matsuo Yasumitsu , Ikehata Seiichiro , Ito Takuo , Komukae Masaru , Osaka Toshio
Published: December 2003

In this paper we first present recent experimental results related to superionic conduction in the zero‐dimensional hydrogen‐bonded crystals of alkali‐hydrosulfates or hydroselenates, M3H(XO4)2 [M = K, Rb, Cs and X = S, Se]. Then a novel approach to the mechanism of proton conduction in the paraelastic phase is described. The key features of the conduction mechanism in the high temperature paraelastic phase which we call the superionic phase are: (1) Two kinds of ionic states, H2XO4(+e) and XO4(−e) are formed by breaking a hydrogen‐bond thermally; (2) H2XO4(+e) and XO4(−e) ionic states move coherently from an XO4 tetrahedron to a distant XO4 as the result of successive proton tunneling among the hydrogen bonds. We calculate the density of states for the coherent motions of these ionic states by the recursion formula. From this result we show that a characteristic feature of the band‐like states obtained from itinerancy of H2XO4(+e) and XO4(−e) ionic states is that of the Bethe lattice; that is the appearance of the twin peak structure due to self‐similarity. The calculated conductivity is very high such as the order of 10−2 S/cm at and above Tc, consistent with experiment. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric‐field‐induced hopping transport in superlattices
Authors: Kleinertand P. , Bryksin V. V.
Published: December 2003

A strong electric field applied parallel to the superlattice axis leads to Wannier–Stark localization. There are two formally equivalent pictures for the drift velocity and the diffusion coefficient, the hopping model, which is most suitable for localized states, and the band picture, which is applicable to extended states. Complete localization of carriers is achieved by strong electric and magnetic fields. In these molecule‐like systems, there is a strong interdependence between the carrier spectrum and its statistical properties, the description of which requires a new approach. The related double‐time character of the transport gives rise to interesting quantum effects in the current–voltage characteristics. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Are the interaction effects responsible for the temperature and magnetic field dependent conductivity in Si‐MOSFETs?
Authors: Pudalov V. M. , Gershenson M. E. , Kojima H. , Brunthaler G. , Bauer G.
Published: December 2003

We compare the temperature and in‐plane magnetic field dependences of resistivity ρ (T, B∥) of Si MOSFETs with the recent theories. In the comparison we use the effective mass m* and g*‐factor determined independently. An anomalous increase of ρ with temperature, which has been considered a signature of the “metallic” state, for high conductivities (σ > e2/h) can be described quantitatively by the interaction effects in the ballistic regime. ρ(B∥) is consistent with the theory only qualitatively; it is found to be more susceptible than ρ(T) to details of disorder, possibly associated with magnetic moments of localized states. Description of the transport in the “critical” regime of ρ ∼ h/e2 is still lacking. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic ordering in doped semiconductors near the metal–insulator transition
Authors: Zabrodskii A. G.
Published: December 2003

Experiment clearly shows a certain extent of ordering of localized magnetic moments in doped semiconductors near the metal–insulator transition. An antiferromagnetic spin glass structure is revealed in a number of n‐type materials (Ge:As, 6H‐ and 4H‐SiC:N) by Electron Spin Resonance spectroscopy as a sharp decrease in the density of paramagnetic centres, observed when approaching the transition from its insulator side. In a p‐type material (Ge:Ga), the macroscopic magnetization and residual magnetization, as well as hole coupling in pairs or clusters with uncompensated moment, follow from the recently discovered hysteresis of variable range hopping magnetoresistance, accompanied by sharp drops in resistance on reversing the magnetization of the system. The location of the magnetically ordered phases is established. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Possibility of superconductivity in intercalation compound related to MgB2
Authors: Kato Nobuhiko , Nagao Hidemi , Nishikawa Kiyoshi , Nishidate Kazume , Endo Kazunaka
Published: December 2003

We investigated the electronic structure of MgB2 and intercalation compounds, MgBX (X = Li, Be, C), with fully relaxed crystal structure by using density functional theory. The compounds MgBLi and MgBBe could be similar two‐band superconductors to MgB2 because the Fermi surface crosses σ and π bands. Our results indicate that changing the lattice constants, hole or electron doping, and stacking of BX effect the energy levels of the σ and π bands in MgBX compounds. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Semiclassic approach within the He atom sphere model
Authors: Kiselyov A. A.
Published: December 2003

The helium atom doubly excited‐states energy levels are calculated for the 1S‐state. The He atom is considered as the three‐atomic molecule. The electrons are supposed to move on the sphere of the equal radius. The rotation is described by the Euler angles, which can be divided in a standard way. Then, the hyperspherical coordinates are introduced. The adiabatic approach allows us to solve the equation on interelectron angle θ. We used the contour integral method for this equation. The equation on the hyperradius R was solved according to the semiclassic approach. The obtained results are in good agreement with those of some other works. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Mean‐field potential approach to the quasiharmonic theory of solids
Authors: Wang Y. , Ahuja R. , Johansson B.
Published: December 2003

Adopting the quasiharmonic approximation, a newly developed classical mean‐field potential (MFP) approach is extended to the quantum case. Two new Debye temperature expressions, which are in accordance with the thermodynamic theory of Dugdale and MacDonald and with the free volume theory, respectively, are derived in addition to the well‐known expression of Slater. The Grüneisen law is now implied explicitly in the Debye temperature expression, and therefore no additional conditions for the Grüneisen constant are needed for realistic thermodynamic calculations. The thermal expansion and specific heat of Na, Cu, Mo, Ta, and Th have been calculated from 10 K up to the melting point. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Approximate on‐top pair density into one‐body functions for CAS‐DFT
Authors: Takeda R. , Yamanaka S. , Yamaguchi K.
Published: December 2003

We have derived the new expression of the on‐top pair density of CAS [2,2] by one‐body functions of natural orbitals and these occupation numbers, which we call one‐body representation of second‐order density (ORSOD). The expression allows us to drastically reduce the computational cost of complete‐active‐space density functional theory. Furthermore, we define the ionic density as an approximation of ORSOD for description of potential surfaces exhibiting ionic character. We have applied these schemes for the dissociation curves of H2 and F2 molecules. The relation between the ORSOD, the ionic‐density, and the radical‐electron density that is defined in our previous work is also discussed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Rhinovirus and the lower respiratory tract
Authors: Hayden Frederick G.
Published: January 2004

Human rhinoviruses (HRVs) are well‐recognised causes of common colds and associated upper respiratory tract complications such as sinusitis and otitis media. This article reviews information linking HRV infection to illness in the lower respiratory tract. HRVs are capable of efficient replication in vitro at temperatures present in the tracheobronchial tree and have been shown to cause productive infection, elaboration of cytokines and chemokines, and up‐regulation of cell surface markers in human bronchial epithelial cells. In situ hybridisation studies have proven that HRV infection occurs in the tracheobronchial tree following experimental infection. Clinical studies report that HRV infection is the second most frequently recognised agent associated with pneumonia and bronchiolitis in infants and young children and commonly causes exacerbations of pre‐existing airways disease in those with asthma, chronic obstructive pulmonary disease or cystic fibrosis. HRV infection is associated with one‐third to one‐half of asthma exacerbations depending on age and is linked to asthma hospitalisations in both adults and children. Limited information implicates HRV infection as a cause of severe lower respiratory tract illness in older adults and in highly immunocompromised hosts, particularly bone marrow transplant recipients. More information is needed about the pathogenesis of HRV infection with regard to lower respiratory tract complications in these diverse patient groups. Given the large unmet medical need associated with HRV infections, safe and effective antiviral agents are needed for both prevention and treatment of these infections. Copyright © 2004 John Wiley & Sons, Ltd.
Prospects for antiviral ribozymes and deoxyribozymes
Authors: Peracchi Alessio
Published: January 2004

Ribozymes and deoxyribozymes (collectively referred to as nucleic acid enzymes) can be designed to cleave substrate mRNAs in a sequence‐specific manner, and thus represent a potentially important tool to inhibit selectively the expression of deleterious genes. Nucleic acid enzymes can be delivered to cells either as genes encoding RNA enzymes (ribozymes), or exogenously as in vitro produced agents. This review focuses in particular on the ‘exogenous application’ of ribozymes and deoxyribozymes as antiviral drugs.

In the past few years, the therapeutic development of ribozymes and deoxyribozymes has encountered a variety of problems, several of which have now been solved thanks to a massive amount of research. Much progress has been made towards understanding the structure and mechanism of these catalysts, improving their stability and effectiveness in vivo, and investigating their clinical usage. Despite this, it is not yet clear whether these molecules can be developed into clinically useful pharmaceutical preparations. To address the long‐term prospects of this class of therapeutics, it is necessary to consider their intrinsic capabilities and limits, the developmental difficulties that they still face and the comparative advantages and disadvantages they may offer with respect to other oligonucleotide‐based therapeutic approaches. Copyright © 2004 John Wiley & Sons, Ltd.
Syntheses and Characterization of Mixed‐Anions Lead(II) Complexes, [Pb(phen)2(CH3COO)]X (X=NCS—, NO3— and ClO4—), Crystal Structure of [Pb(phen)2(CH3COO)](ClO4)
Authors: Morsali Ali , Mahjoub Ali R. , Darzi Simin Janitabar , Soltanian Mohammad J.
Published: December 2003

The 1:2 adduct lead(II) complexes with 1, 10‐phenanthroline (phen) containing three different anions, [Pb(phen)2(CH3COO)X] (X=NCS—, NO3— and ClO4—), have been synthesized and characterized by CHN elemental analysis, IR‐, 1H‐ and 13C NMR spectroscopy. The structure of [Pb(phen)2(CH3COO)(ClO4)] was determined by single crystal X‐ray analysis. The Pb atom of the monomeric complex is coordinated by four nitrogen atoms of two 1, 10‐phenanthroline ligands and two oxygen atoms of the acetate ligand to form an irregular octahedron. The arrangement of the 1, 10‐phenanthroline and acetate ligands, exhibits a coordination gap around the PbII ion, possibly occupied by a stereochemical electron active lone pair on lead(II), which results in a hemidirected lead compound. The π‐π stacking interaction between the parallel aromatic rings may help to increase the coordination ‘gap’ around the PbII ion.
The Reaction of 2‐X‐1, 2‐Difluoroalk‐1‐enyldifluoroboranes with Xenon Difluoride. A Methodical Approach to 1, 2‐Difluoroalk‐1‐enylxenon(II) Salts
Authors: Frohn Hermann‐Josef , Adonin Nicolay Yu. , Bardin Vadim V.
Published: December 2003

2‐X‐1, 2‐Difluoroalk‐1‐enylxenon(II) salts were prepared by the reaction of XeF2 with XCF=CFBF2 (X = F, trans‐H, cis‐Cl, trans‐Cl, cis‐CF3, cis‐C2F5) but no organoxenon(II) compounds were obtained when the trans‐isomers of boranes, trans‐XCF=CFBF2 (X = CF3, C4F9, C4H9, Et3Si), were used under similar conditions.
Synthesis and Structure of a Molecular Zinc Phosphate [(C12H8N2Zn)2(HPO4)(H2PO4)2]
Authors: Ganesan S. V. , Thirumurugan A. , Natarajan Srinivasan
Published: December 2003

A hydrothermal reaction of a mixture of ZnCO3, phosphoric acid, 1, 10‐phenanthroline in H2O gave rise to large plates of a new zinc phosphate, [(C12H8N2Zn)2(HPO4)(H2PO4)2], I. The structure consists of ZnO3N2 distorted trigonal‐bipyramidal and PO4 tetrahedral units linked through their vertices to give rise to a zero‐dimensional molecular solid (monomer). The structure of the monomer appears to be similar to the secondary building unit (SBU) 4 = 1, commonly found in many fibrous zeolites. To our knowledge, this is the first time this building unit has been isolated. The structure, with a unique composition, is stabilized by hydrogen bond interactions between the terminal —OH groups forms a one‐dimensional molecular wire and also by strong π…π interactions between the 1, 10‐phenanthroline units. Photoluminescence studies show that there is a ligand‐to‐metal charge transfer (LMCT). Crystal data: orthorhombic, space group = Fdd2 (no. 43), a = 40.4669(1), b = 7.4733(2), c = 17.4425(5)Å, V = 5274.9(2)Å3, Z = 8.
Synthesis and Structure of High‐Nuclearity Bimetallic Clusters containing Polycyanometallate Cores capped by [NiII(pyN4)] Fragments
Authors: López Jesús Pitarch , Heinemann Frank W. , Grohmann Andreas
Published: December 2003

The use of the pyN4 coordination cap to synthesize high‐nuclearity clusters supported by polycyanometallate units was explored. The heptanuclear bimetallic complexes 2 and 3 were obtained as their salts by reacting stoichiometric amounts of pyN4 and Ni(ac)2 with K3[Fe(CN)6] and K4[Mo(CN)8], respectively. The tetranuclear complex 4 formed as a by‐product in the synthesis of 3. Temperature‐dependent magnetic susceptibility measurements carried out for 2 revealed that this compound behaves as a paramagnet over the whole range of temperatures.
Syntheses, Structures, and Properties of Lanthanide Supramolecular Complexes with 1, 10‐Phenanthroline and Terminal Amino Acids with Different Chain Lengths
Authors: Zheng Xiangjun , Jin Linpei , Lu Shaozhe , Zheng Yueqing
Published: December 2003

Four lanthanide supramolecular coordination compounds, [Eu(gly)2(phen)2(H2O)2](ClO4)3(phen)4 · H2O (1), [Eu2(APA)6(phen)2](ClO4)6(phen)4 · 3H2O (2), [Tb2(ABA)4(phen)4](ClO4)6(phen)4 (3), and [Eu2(AHA)4(phen)4](ClO4)6(phen)2 · 2H2O · 2C2H5OH (4) (gly = glycine, APA = 3‐aminopropionic acid, ABA = 4‐aminobutanoic acid, AHA = 6‐aminohexanoic acid, phen = 1, 10‐phenanthroline), were synthesized and characterized by single crystal X‐ray diffraction. Compound 1 has a 2‐D supramolecular layered structure of mononuclear coordination cations and free phen molecules connected via hydrogen bonding and π‐π stacking interactions. 2 forms a 3‐D supramolecular network by hydrogen bonding between binuclear coordination cations and free phen molecules, between coordination cations and lattice water molecules, and π‐π stacking interactions between free phen molecules. Compounds 3 and 4 form 2‐D supramolecular structures with π‐π stacking between coordinating phen molecules, and between free phen molecules hydrogen‐bonded to the binuclear coordination cations. The high‐resolution emission spectra show only one Eu3+ ion site in the title complexes. The aqueous solutions of the title complexes are all photochromic with the color of the solution changing from yellow to green when irradiated by mercury lamp. During the decoloration process, they return to yellow color.
Ein Calciumurannitrid — (Ca3U)N4 — mit Natriumchloridstruktur
Authors: Heckers Uwe , Jacobs Herbert , Kockelmann Winfried
Published: December 2003

Mixtures of calcium amide, Ca(NH2)2 and uranium hydride, UH3 were reacted at temperatures between 600 °C and 1000 °C for 2d to 30d. Starting with a mixture 3 : 1 a singlephase, black, microcrystalline product is obtained. As a result of X‐ray and neutron diffraction the phase has the composition (Ca0, 75U0, 25)N = Ca3UN4. It crystallizes in the space group Fm3¯m with a = 4.9398 (1) Å in the sodium chloride structure type with statistical occupation of the cation site 4a by 3Ca and 1U.
Structural Studies of Bis(cyclopentadienyl)molybdenum‐Amino Acid Complexes
Authors: Vujevic Goranka , Janiak Christoph
Published: December 2003

The crystal structures of molybdocene‐amino acid compounds of the type [Cp2MoIV(κN, κO‐AA)]+Cl—·xH2O with AA = D‐phenylalaninato (x = 1.5), DL‐leucinato (x = 2) and DL‐valinato (x = 1) have been determined (Cp = η5‐C5H5). The compounds feature an almost planar, five‐membered chelate ring of the aminocarboxylate moiety (deprotonated amino acid) with the molybdenum atom. In the phenylalaninato complex π‐stacking between the phenyl rings is found. The complexes were proven kinetically stable at pH < 1 for at least 24 h.
Chloroberyllate mit Stickstoff‐Donorliganden. Die Kristallstrukturen von (Ph4P)[BeCl3(Py)], (Ph4P)2[(BeCl3)2(TMEDA)], (Ph4P)[BeCl2{(Me3SiN)2CPh}] und (Ph4P)2[BeCl4] · 2CH2Cl2
Authors: Neumüller Bernhard , Dehnicke Kurt
Published: December 2003

Die im Titel genannten Chloroberyllate entstehen als farblose, feuchtigkeitsempfindliche Kristalle durch Umsetzungen von (Ph4P)2[Be2Cl6] mit Pyridin, TMEDA (N, N′‐Tetramethylethylendiamin) oder dem silylierten Benzamidin PhC[N(SiMe3)2(NSiMe3)], während das Tetrachloroberyllat als Nebenprodukt aus Dichlormethanlösung in Gegenwart des silylierten Phosphanimins Me3SiNP(Tolyl)3 kristallisiert. Alle Verbindungen werden durch Kristallstrukturanalysen und IR‐Spektren charakterisiert.

(Ph4P)[BeCl3(Py)] (1): Raumgruppe Pbcm, Z = 4, Gitterkonstanten bei 193 K: a = 756, 2(1); b = 1739, 2(2); c = 2016, 3(2) pm, R1 = 0, 0626. Das komplexe Anion enthält tetraedrisch koordiniertes Berylliumatom mit einem Be—N‐Abstand von 176, 5 pm.

(Ph4P)2[(BeCl3)2(TMEDA)]·2CH2Cl2 (2·2CH2Cl2). Raumgruppe P1¯, Z = 1, Gitterkonstanten bei 193 K: a = 1072, 7(1); b = 1132, 6(1); c = 1248, 9(1) pm, α = 95, 34(1)°; β = 92, 80(1)°; γ = 90, 81(1)°; R1 = 0, 0344. Im komplexen zentrosymmetrischen Anion sind beide N‐Atome des TMEDA‐Moleküls durch BeCl3—‐Einheiten koordiniert mit Be—N‐Abständen von 181, 3 pm.

(PPh4)[BeCl2{(Me3SiN)2CPh}] (3). Raumgruppe C2, Z = 2, Gitterkonstanten bei 193 K: a = 1255, 4(2); b = 1401, 9(2); c = 1085, 2(2) pm, R1 = 0, 0288. In dem komplexen Anion fungiert der Benzamidinatoligand {(Me3SiN)2CPh}— als Chelat mit Be—N‐Abständen von 174, 9 pm.

(Ph4P)2[BeCl4]·2CH2Cl2 (4·2CH2Cl2). Raumgruppe P2/c, Z = 4, Gitterkonstanten bei 193 K: a = 2295, 4(1); b = 982, 5(1); c = 2197, 2(2) pm, β = 99, 19(1)°, R1 = 0, 0586. 4·2CH2Cl2 enthält wie das früher beschriebene 4·2, 5CH2Cl2, das in der Raumgruppe P1¯ kristallisiert, nahezu idealtetraedrische [BeCl4]2—‐Ionen mit gemittelten Be—Cl‐Abständen von 203, 4 pm.
Density Functional Theory Calculations of the Barrier to Atropisomerism of a Dibenzo[d, f][1, 3, 2]dioxaphosphepin Moiety: a Tool for Rational Ligand Design
Authors: Franke Robert , Borgmann Cornelia , Hess Dieter , Wiese Klaus‐Diether
Published: December 2003

Density functional theory calculations yield reasonable values for the barrier to atropisomerism in a dibenzo[d, f][1, 3, 2]dioxaphosphepin moiety of diphosphite ligands and thus provide an energetic criterion for falsification of hypothetical stable stereoisomers in rational ligand design.
Coordination of Bimuth(III) to Cucurbit[8]uril. Preparation and X‐ray Structure of [{Bi(NO3)(H2O)5}2(Q8)][Bi(NO3)3(H2O)4]2[Bi(NO3)5]2·Q8·19H2O
Authors: Sokolov Maxim N. , Mitkina Tatyana V. , Gerasko Olga A. , Fedin Vladimir P. , Virovets Alexandr V. , Llusar R.
Published: December 2003

Bi(NO3)3 reacts with cucurbit[8]uril, (Q8), in 3M HNO3 to give the title complex whose structure includes three discrete Bi complexes: [{Bi(NO3)(H2O)5}2(Q8)]4+ (CN of Bi = 9, both NO3— and cucurbit[8]uril are bidentate), [Bi(NO3)5]2— (CN of Bi = 10, all NO3— are bidentate), and [Bi(NO3)3(H2O)4] (CN of Bi = 10, all NO3— are bidentate).