bluuebunny/crossref_metadata_2025 huggingface dataset:
Lv1 Inhibition of Human Immunodeficiency Virus Type 1 Is Counteracted by Factors That Stimulate Synthesis or Nuclear Translocation of Viral cDNA
Authors: Berthoux Lionel , Sebastian Sarah , Sokolskaja Elena , Luban Jeremy
Published: October 2004

Human immunodeficiency virus type 1 (HIV-1) cDNA synthesis is inhibited in cells from some nonhuman primates by an activity called Lv1. Sensitivity to restriction by Lv1 maps to a region of the HIV-1 CA required for interaction with the cellular protein cyclophilin A. A similar antiviral activity in mammalian cells, Ref1, inhibits reverse transcription of murine leukemia virus (MLV), but only with viral strains bearing N-tropic CA. Disruption of the HIV-1 CA-cyclophilin A interaction inhibits Lv1 restriction in some cells and, paradoxically, seems to render HIV-1 sensitive to Ref1. Lv1 and Ref1 activities are overcome by high-titer infection and are saturable with nonreplicating, virus-like particles encoded by susceptible viruses. Two compounds that disrupt mitochondrial membrane potential, As
2
O
3
and m-Cl-CCP, reduce Ref1 activity. Here we show that these drugs, as well as a third compound with similar effects on mitochondria, PK11195, attenuate Lv1 activity in rhesus macaque and African green monkey cells. Effects of PK11195 and virus-like particles on HIV-1 infectivity in these cells were largely redundant, each associated with increased HIV-1 cDNA. Comparison of acutely infected macaque and human cells suggested that, in addition to effects on cDNA synthesis, Lv1 inhibits the accumulation of nuclear forms of HIV-1 cDNA. Disruption of the HIV-1 CA-cyclophilin A interaction caused a minimal increase in total viral cDNA but increased the proportion of viral cDNA in the nucleus. Consistent with a model in which Lv1 inhibits both synthesis and nuclear translocation of HIV-1 cDNA, complete suppression of macaque or African green monkey Lv1 was achieved by the additive effect of factors that stimulate both processes.
Between-Host Evolution of Cytotoxic T-Lymphocyte Epitopes in Human Immunodeficiency Virus Type 1: an Approach Based on Phylogenetically Independent Comparisons
Authors: Piontkivska Helen , Hughes Austin L.
Published: October 2004

In human immunodeficiency virus type 1 (HIV-1), mutations that escape from cytotoxic T-lymphocyte (CTL) recognition have been documented, and sequence analyses have provided indirect support for the hypothesis that natural selection has favored CTL escape mutants within an infected host. In spite of such evidence for within-host selection by CTL, it has been more difficult to determine how natural selection by host CTL has influenced long-term evolution of HIV-1. We used statistical analysis of published HIV-1 genomic sequences to examine the role of natural selection in between-host evolution of CTL epitopes. Based on a phylogenetic analysis, we identified 21 pairs of closely related genomes isolated from different hosts and examined the pattern of nucleotide substitution in genomic regions encoding well-characterized CTL epitopes. The results revealed that certain CTL epitopes have been subject to repeated positive selection across the population, while others are generally conserved. Furthermore, evidence of positive selection was associated with divergence from the canonical epitope sequence and with an enhanced frequency of convergent amino acid sequence changes in CTL epitopes. The results support the hypothesis that CTL-driven selection has been a major factor in the long-term evolution of HIV-1.
Coevolution of RANTES Sensitivity and Mode of CCR5 Receptor Use by Human Immunodeficiency Virus Type 1 of the R5 Phenotype
Authors: Karlsson Ingrid , Antonsson Liselotte , Shi Yu , Öberg Monica , Karlsson Anders , Albert Jan , Olde Björn , Owman Christer , Jansson Marianne , Fenyö Eva Maria
Published: October 2004

The evolution of human immunodeficiency virus type 1 (HIV-1) coreceptor use has been described as the acquisition of CXCR4 use linked to accelerated disease progression. However, CXCR4-using virus can be isolated only from approximately one-half of individuals with progressive HIV-1 disease. The other half continue to yield only CCR5-using viruses (R5 phenotype) throughout the course of disease. In the present work, the use of receptor chimeras between CCR5 and CXCR4 allowed us to study the evolution of HIV-1 with the R5 phenotype, which was not revealed by studies of wild-type coreceptor use. All together, 246 isolates (173 with the R5 phenotype) from 31 individuals were tested for their ability to infect cells through receptor chimeras. R5
narrow
virus was able to use only wild-type CCR5, whereas R5
broad(1)
to R5
broad(3)
viruses were able to use one to three chimeric receptors, respectively. Broad use of chimeric receptors was interpreted as an increased flexibility in the mode of receptor use. R5
broad
isolates showed higher infectivity in cells expressing wild-type CCR5 than R5
narrow
isolates. Also, the increased flexibility of R5
broad
isolates was concomitant with a lower sensitivity to inhibition by the CC chemokine RANTES. Our results indicate a close relationship between HIV-1 phenotypic changes and the pathogenic process, since the mode and efficiency of CCR5 use as well as the decrease in the RANTES sensitivities of isolated viruses are significantly correlated with CD4
+
-T-cell decline in a patient. One possible explanation is that ligand competition at the CCR5 receptor or changed CCR5 availability may shape the outcome of HIV-1 infection.
Stable Ubiquitination of Human T-Cell Leukemia Virus Type 1 Tax Is Required for Proteasome Binding
Authors: Chiari Estelle , Lamsoul Isabelle , Lodewick Julie , Chopin Cécile , Bex Françoise , Pique Claudine
Published: October 2004

Human T-cell leukemia virus type 1 (HTLV-1) is the retrovirus responsible for adult T-cell leukemia and HTLV-1-associated myelopathy. Adult T-cell leukemia development is mainly due to the ability of the viral oncoprotein Tax to promote T-cell proliferation, whereas the appearance of HTLV-1-associated myelopathy involves the antigenic properties of Tax. Understanding the events regulating the intracellular level of Tax is therefore an important issue. How Tax is degraded has not been determined, but it is known that Tax binds to proteasomes, the major sites for degradation of intracellular proteins, generally tagged through polyubiquitin conjugation. In this study, we investigated the relationship between Tax, ubiquitin, and proteasomes. We report that mono- and polyubiquitinated Tax proteins can be recovered from both transfected 293T cells and T lymphocytes. We also show that lysine residues located in the carboxy-terminal domain of Tax are the principal targets of this process. Remarkably, we further demonstrate that mutation of lysine residues in the C-terminal part of Tax, which massively reduces Tax ubiquitination, impairs proteasome binding, and conversely, that a Tax mutant that binds poorly to this particle (M22) is faintly ubiquitinated, suggesting that Tax ubiquitination is required for association with cellular proteasomes. Finally, we document that comparable amounts of ubiquitinated species were found whether proteasome activities were inhibited or not, providing evidence that they are not directly addressed to proteasomes for degradation. These findings indicate that although it is ubiquitinated and binds to proteasomes, Tax is not massively degraded via the ubiquitin-proteasome pathway and therefore reveal that Tax conjugation to ubiquitin mediates a nonproteolytic function.
Calcium-Dependent Calpain Proteases Are Implicated in Processing of the Hepatitis C Virus NS5A Protein
Authors: Kalamvoki M. , Mavromara P.
Published: October 2004

The nonstructural 5A (NS5A) protein of the hepatitis C virus (HCV) is a multifunctional phosphoprotein that is implicated in viral replication and HCV-mediated pathogenesis. We report here that the NS5A protein from the HCV genotype 1a is processed into shorter distinct forms when expressed in mammalian cells (Vero, HepG2, HuH-7, and WRL68) infected with an NS5A-expressing HSV-1-based amplicon vector or when transiently transfected with NS5A-expressing plasmids in the absence of exogenous apoptotic stimuli. Inhibitor studies combined with cell-free cleavage assays suggest that calcium-dependent calpain proteases, in addition to caspase-like proteases, are involved in NS5A processing. Interestingly, His-tagging experiments indicated that all the detectable NS5A-cleaved products are N-terminal forms of the protein. Additionally, immunofluorescence studies showed that, despite proteolytic cleavage, the NS5A protein exhibits a cytoplasm-perinuclear localization similar to that of the full-length protein. Thus, our results are consistent with recent data that demonstrated that NS5A is capable of perturbing intracellular calcium homeostasis and suggest that NS5A is both an inducer and a substrate of the calcium-dependent calpain protease(s). This may imply that cleavage of NS5A by calpain(s) could play a role in the modulation of NS5A function.
Essential Function of the Pseudorabies Virus UL36 Gene Product Is Independent of Its Interaction with the UL37 Protein
Authors: Fuchs Walter , Klupp Barbara G. , Granzow Harald , Mettenleiter Thomas C.
Published: October 2004

The large tegument protein encoded by the UL36 gene of pseudorabies virus (PrV) physically interacts with the product of the adjacent UL37 gene (B. G. Klupp, W. Fuchs, H. Granzow, R. Nixdorf, and T. C. Mettenleiter,
J. Virol.
76:
3065-3071, 2002). To analyze UL36 function, two PrV recombinants were generated by mutagenesis of an infectious PrV full-length clone in
Escherichia coli
: PrV-ΔUL36F exhibited a deletion of virtually the complete UL36 coding region, whereas PrV-UL36BSF contained two in-frame deletions of 238 codons spanning the predicted UL37 binding domain. Coimmunoprecipitation experiments confirmed that the mutated gene product of PrV-UL36BSF did not interact with the UL37 protein. Like the previously described PrV-ΔUL37 (B. G. Klupp, H. Granzow, and T. C. Mettenleiter,
J. Virol.
75:
8927-8936, 2001) but in contrast to PrV-ΔUL36F, PrV-UL36BSF was able to replicate in rabbit kidney (RK13) cells, although maximum virus titers were reduced ca. 50-fold and plaque diameters were reduced by ca. 45% compared to wild-type PrV. PrV-ΔUL36F was able to productively replicate after repair of the deleted gene or in a
trans
-complementing cell line. Electron microscopy of infected RK13 cells revealed that PrV-UL36BSF and phenotypically complemented PrV-ΔUL36F were capable of nucleocapsid formation and egress from the nucleus by primary envelopment and deenvelopment at the nuclear membrane. However, reenvelopment of nucleocapsids in the cytoplasm was blocked. Only virus-like particles without capsids were released efficiently from cells. Interestingly, cytoplasmic nucleocapsids of PrV-UL36BSF but not of PrV-ΔUL36F were found in large ordered structures similar to those which had previously been observed with PrV-ΔUL37. In summary, our results demonstrate that the interaction between the UL36 and UL37 proteins is important but not strictly essential for the formation of secondary enveloped, infectious PrV particles. Furthermore, UL36 possesses an essential function during virus replication which is independent of its ability to bind the UL37 protein.
Interaction between the Cytoplasmic Domain of ICAM-1 and Pr55
Gag
Leads to Acquisition of Host ICAM-1 by Human Immunodeficiency Virus Type 1
Authors: Beauséjour Yannick , Tremblay Michel J.
Published: October 2004

We have examined the molecular basis for the selective incorporation of the adhesion molecule ICAM-1 within human immunodeficiency virus type 1 (HIV-1). The process of ICAM-1 incorporation was investigated by using different ICAM-1 constructs in combination with virus capture and immunoprecipitation studies, Western blot and confocal microscopy analyses, and infectivity assays. Experiments conducted with viruses bearing a truncated version of ICAM-1 revealed that the cytoplasmic domain of ICAM-1 governs insertion of this adhesion molecule into HIV-1. Further experiments suggested that there is an association between ICAM-1 and the virus-encoded Pr55
Gag
polyprotein. This study represents the first demonstration that structural Gag polyproteins play a key role in the uptake of a host-derived cell surface by the virus entity. Taken together, our results indicate that interactions between viral and cellular proteins are responsible for the selective uptake of host ICAM-1 by HIV-1. This observation describes a new strategy by which HIV-1 can modulate its replicative cycle, considering that insertion of ICAM-1 within nascent virions has been shown to increase virus infectivity.
Activation of Transcription Factor Nrf-2 and Its Downstream Targets in Response to Moloney Murine Leukemia Virusts1-Induced Thiol Depletion and Oxidative Stress in Astrocytes
Authors: Qiang Wenan , Cahill Jodi M. , Liu Jinrong , Kuang Xianghong , Liu Na , Scofield Virginia L. , Voorhees Jennifer R. , Reid Amy J. , Yan Mingshan , Lynn William S. , Wong Paul K. Y.
Published: October 2004

The neuroimmunodegenerative syndrome that develops in mice infected withts1, a mutant of Moloney murine leukemia virus, resembles human AIDS. Bothts1 and human immunodeficiency virus type 1 infect astrocytes, microglia, and oligodendrocytes but do not infect neurons. Oxidative stress has been implicated in the neuropathology of AIDS dementia and other neurodegenerative diseases. We report here thatts1 infection of astrocytes (both transformed C1 cells and primary cultures) also induces thiol (i.e., glutathione and cysteine) depletion and reactive oxygen species (ROS) accumulation, events occurring in parallel with viral envelope precursor gPr80envaccumulation and upregulated expression of endoplasmic reticulum chaperones GRP78 and GRP94. Furthermore,ts1-infected astrocytes mobilize their thiol redox defenses by upregulating levels of the Nrf-2 transcription factor, as well its targets, the xCT cystine/glutamate antiporter, γ-glutamylcysteine ligase, and glutathione peroxidase. Depleting intracellular thiols by treating uninfected astrocytes with buthionine sulfoximine (BSO), a glutathione synthesis inhibitor, or by culturing in cystine-deficient medium, also induces ROS accumulation, activates Nrf-2, and upregulates Nrf-2 target gene expression in these astrocytes. Overexpression of Nrf-2 in astrocytes specifically increases expression of the above thiol synthesis-related proteins. Further treatment with BSO orN-acetylcysteine in transfected cells modulates this expression. Thiol depletion also accelerates cell death, while thiol supplementation promotes survival ofts1-infected cells. Together, our results indicate thatts1 infection of astrocytes, along withts1-induced gPr80envaccumulation, endoplasmic reticulum stress, thiol depletion, and oxidative stress, accelerates cell death; in response to the thiol depletion and oxidative stress, astrocytes activate their Nrf-2-mediated thiol antioxidant defenses, promoting cell survival.
Early Stage of Establishment of Persistent Sendai Virus Infection: Unstable Dynamic Phase and Then Selection of Viruses Which Are Tightly Cell Associated, Temperature Sensitive, and Capable of Establishing Persistent Infection
Authors: Ito Morihiro , Takeuchi Taijiro , Nishio Machiko , Kawano Mitsuo , Komada Hiroshi , Tsurudome Masato , Ito Yasuhiko
Published: October 2004

We obtained 157 cloned cell lines persistently infected with Sendai virus; these cell lines were generated independently of each other. Infectious viruses could be isolated from 123 of these cloned cell lines by inoculation of culture fluids or infected cells into embryonated eggs. The majority of the viruses carried by cells persistently infected with viruses showed high cytotoxicity and did not have the ability to establish persistent infection. The association of carried virus with cells became stronger and virus isolation correspondingly became more difficult as cells persistently infected with virus were subcultured. Viruses derived from virus-infected cells eventually acquired the ability to establish persistent infection, although the ways in which the viruses acquired this ability varied. The viruses also acquired temperature sensitivity as persistently infected cells were subcultured. First, the hemagglutinin-neuraminidase and M proteins acquired temperature sensitivity, and then the polymerase(s) did so. The M proteins were localized in the nuclei of cells infected with cloned viruses that had the ability to establish persistent infection. Cells infected with viruses capable of establishing persistent infection showed no or slight staining by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling. Specific amino acid substitutions accumulated in the M protein and the L protein as virus-infected cells were subcultured. This study shows that there is an unstable dynamic phase at an early stage of the establishment of persistent Sendai virus infection (steady state), and then viruses capable of establishing persistent infection are selected.
Identification of a Negative Regulatory Element in the Epstein-Barr Virus Zta Transactivation Domain That Is Regulated by the Cell Cycle Control Factors c-Myc and E2F1
Authors: Lin Zhen , Yin Qinyan , Flemington Erik
Published: October 2004

Reactivation in Epstein-Barr virus (EBV) is closely associated with a G
0
/G
1
cell cycle arrest which can be induced either by lytic cycle-inducing agents or by the immediate-early gene product Zta. Accumulating evidence shows that in epithelial cells, downregulation of the proto-oncogene, c-
myc
, plays an important role in lytic cycle-associated cell growth arrest. Here, we provide evidence that c-Myc provides a gatekeeper function to ensure that certain cell cycle inhibitory events have been capitulated prior to full progression into the lytic cycle. Specifically, we show that reconstitution of c-Myc expression during the lytic cycle to levels observed in cycling uninduced cells inhibits the transactivation function of Zta. Nuclear localization studies show that c-Myc does not grossly alter the nuclear localization of Zta or its association with the insoluble nuclear fraction. Enforced expression of another transcription factor that promotes cell cycle progression, E2F1, also inhibits Zta transactivation. Analysis of c-Myc- and E2F1-mediated inhibition of a panel of Zta mutants shows parallel genetics and inhibition maps to a small bipartite sequence located between amino acids 29 and 53 of Zta, containing homology to the proline-rich domain of the tumor suppressor protein p53. Mutation of a conserved tryptophan residue located at amino acid 49 of Zta largely prevents inhibition by both c-Myc and E2F1. These studies identify a negative regulatory element within the Zta activation domain that is regulated by the cell cycle-promoting factors c-Myc and E2F1.
Structural and Thermodynamic Basis for the Binding of TMC114, a Next-Generation Human Immunodeficiency Virus Type 1 Protease Inhibitor
Authors: King Nancy M. , Prabu-Jeyabalan Moses , Nalivaika Ellen A. , Wigerinck Piet , de Béthune Marie-Pierre , Schiffer Celia A.
Published: October 2004

TMC114, a newly designed human immunodeficiency virus type 1 (HIV-1) protease inhibitor, is extremely potent against both wild-type (wt) and multidrug-resistant (MDR) viruses in vitro as well as in vivo. Although chemically similar to amprenavir (APV), the potency of TMC114 is substantially greater. To examine the basis for this potency, we solved crystal structures of TMC114 complexed with wt HIV-1 protease and TMC114 and APV complexed with an MDR (L63P, V82T, and I84V) protease variant. In addition, we determined the corresponding binding thermodynamics by isothermal titration calorimetry. TMC114 binds approximately 2 orders of magnitude more tightly to the wt enzyme (

K
d

= 4.5 × 10
−12
M) than APV (

K
d

= 3.9 × 10
−10
M). Our X-ray data (resolution ranging from 2.2 to 1.2 Å) reveal strong interactions between the
bis
-tetrahydrofuranyl urethane moiety of TMC114 and main-chain atoms of D29 and D30. These interactions appear largely responsible for TMC114's very favorable binding enthalpy to the wt protease (−12.1 kcal/mol). However, TMC114 binding to the MDR HIV-1 protease is reduced by a factor of 13.3, whereas the APV binding constant is reduced only by a factor of 5.1. However, even with the reduction in binding affinity to the MDR HIV protease, TMC114 still binds with an affinity that is more than 1.5 orders of magnitude tighter than the first-generation inhibitors. Both APV and TMC114 fit predominantly within the substrate envelope, a property that may be associated with decreased susceptibility to drug-resistant mutations relative to that of first-generation inhibitors. Overall, TMC114's potency against MDR viruses is likely a combination of its extremely high affinity and close fit within the substrate envelope.
Functional Correlation of P-Glycoprotein Expression and Genotype with Expression of the Human Immunodeficiency Virus Type 1 Coreceptor CXCR4
Authors: Owen Andrew , Chandler Becky , Bray Patrick G. , Ward Stephen A. , Hart C. Anthony , Back David J. , Khoo Saye H.
Published: October 2004

The aim of this study was to investigate the relationship between lymphocyte P-glycoprotein (P-gp) expression and genotype in vivo and the expression of lymphocyte receptors critical in the life cycle of human immunodeficiency virus type 1 (HIV-1), i.e., CD4, CCR5, and CXCR4. Using flow cytometry to quantify each membrane receptor/transporter, we demonstrate a highly significant correlation between P-gp protein expression and the expression of CXCR4 (rho = 0.874;P< 0.0001). Furthermore, confocal microscopy showed colocalized expression of CXCR4 and P-gp in the lymphocyte membrane. This significant relationship was also apparent at the mRNA level by use of reverse transcription-PCR (rho = 0.61;P< 0.005) and was present in both phytohemagglutinin-stimulated and unstimulated peripheral blood mononuclear cells. Genotypic analysis of the C3435T single-nucleotide polymorphism of P-gp confirmed significantly higher levels of P-gp in C (range, 2.45 to 11.00 relative fluorescence units [RFU])- than in T (range, 0.25 to 5.00 RFU)-homozygous individuals (P= 0.0088; 95% confidence interval [95% CI], 0.7 to 6.3 RFU). An equivalent association between CXCR4 levels and C (range, 12.7 to 44.1 RFU) versus T (range, 3 to 18.9 RFU) genotype was also demonstrated (P= 0.0019; 95% CI, 5.4 to 23.7). Functionally, although these correlates had no impact on HIV-1 production from either X4- or R5-tropic virus, expression correlated significantly with the activity of the HIV-1 protease inhibitor (PI) saquinavir for both P-gp (rho = 0.75;P= 0.0019) and CXCR4 (rho = 0.71;P= 0.0041). This study defines an association between P-gp (expression and genotype) and CXCR4 that may have implications for the selection of viral tropism and the access of drugs to protease for specific tropic types. The interplay between these two proteins may also influence the viral genotypes which escape effective chemotherapy and which therefore have the opportunity to evolve resistance to PIs.
Hepatitis C Virus Core Protein Associates with Detergent-Resistant Membranes Distinct from Classical Plasma Membrane Rafts
Authors: Matto Meirav , Rice Charles M. , Aroeti Benjamin , Glenn Jeffrey S.
Published: October 2004

A subpopulation of hepatitis C virus (HCV) core protein in cells harboring full-length HCV replicons is biochemically associated with detergent-resistant membranes (DRMs) in a manner similar to that of markers of classical lipid rafts. Core protein does not, however, colocalize in immunofluorescence studies with classical plasma membrane raft markers, such as caveolin-1 and the B subunit of cholera toxin, suggesting that core protein is bound to cytoplasmic raft microdomains distinct from caveolin-based rafts. Furthermore, while both the structural core protein and the nonstructural protein NS5A associate with membranes, they do not colocalize in the DRMs. Finally, the ability of core protein to localize to the DRMs did not require other elements of the HCV polyprotein. These results may have broad implications for the HCV life cycle and suggest that the HCV core may be a valuable probe for host cell biology.
Statin Compounds Reduce Human Immunodeficiency Virus Type 1 Replication by Preventing the Interaction between Virion-Associated Host Intercellular Adhesion Molecule 1 and Its Natural Cell Surface Ligand LFA-1
Authors: Giguère Jean-François , Tremblay Michel J.
Published: October 2004

A variety of host factors, including membrane proteins acquired by human immunodeficiency virus type 1 (HIV-1), play a dominant role in HIV-1 adsorption onto host cells. Examples include the integrin intercellular adhesion molecule 1 (ICAM-1), which, once acquired by HIV-1, promotes virus infectivity via ligation to LFA-1. We tested the ability of statins to diminish HIV-1 replication, based on the idea that these compounds have been shown to block ICAM-1-LFA-1 interactions. Our data indicate that statins diminish HIV-1 attachment to target cells by suppressing ICAM-1-LFA-1 interactions. The capacity of statins to limit the initial steps in virus replication could represent an interesting approach for the treatment of HIV-1 infection.
Low Level of Lytic Replication in a Recombinant Epstein-Barr Virus Carrying an Origin of Replication Devoid of BZLF1-Binding Sites
Authors: Feederle R. , Delecluse H. J.
Published: October 2004

Binding of the BZLF1 viral transactivator to Epstein-Barr virus (EBV)
oriLyt
has been reported to be essential for viral DNA replication. We have constructed a recombinant virus (E2-
oriLyt-
R) in which the
oriLyt
BZLF1-binding sites (ZRE) were exchanged against papilloma E2-binding sites. A fusion protein between the BZLF1 protein-transactivating domain and the E2 protein-binding domain was able to reactivate lytic replication in E2-
oriLyt-
R. However, BZLF1 alone could also induce E2-
oriLyt-
R, albeit with much lower efficiency. ZRE are therefore important but not absolutely essential
cis
elements for lytic replication. This shows the importance of recombinants to evaluate viral functions.
Genetic Interactions between Hepatitis C Virus Replicons
Authors: Evans Matthew J. , Rice Charles M. , Goff Stephen P.
Published: October 2004

To investigate interactions between hepatitis C virus (HCV) RNA replication complexes, a system was developed to simultaneously select different HCV subgenomic replicons within the same cell. Transcomplementation of defective replicons was not observed, suggesting an isolated and independent nature of the HCV RNA replication complex. In contrast, a high level of competition between replicons was observed, such that the presence and increased fitness of one replicon reduced the capacity of a second one to stably replicate. These results suggest that at least one factor in Huh7 cells required for HCV RNA replication is limiting and saturable.
DC-SIGN and DC-SIGNR Interact with the Glycoprotein of Marburg Virus and the S Protein of Severe Acute Respiratory Syndrome Coronavirus
Authors: Marzi Andrea , Gramberg Thomas , Simmons Graham , Möller Peggy , Rennekamp Andrew J. , Krumbiegel Mandy , Geier Martina , Eisemann Jutta , Turza Nadine , Saunier Bertrand , Steinkasserer Alexander , Becker Stephan , Bates Paul , Hofmann Heike , Pöhlmann Stefan
Published: October 2004

The lectins DC-SIGN and DC-SIGNR can augment viral infection; however, the range of pathogens interacting with these attachment factors is incompletely defined. Here we show that DC-SIGN and DC-SIGNR enhance infection mediated by the glycoprotein (GP) of Marburg virus (MARV) and the S protein of severe acute respiratory syndrome coronavirus and might promote viral dissemination. SIGNR1, a murine DC-SIGN homologue, also enhanced infection driven by MARV and Ebola virus GP and could be targeted to assess the role of attachment factors in filovirus infection in vivo.
${\rm C}^+_{60}$ IONS IN COLLISIONS WITH CRYSTALLINE SURFACES: KINEMATICS AND DYNAMICS
Authors: LILL TH. , BUSMANN H.-G. , LACHER F. , HERTEL I.V.
Published: October 2004

Collisions of [Formula: see text] ions with surfaces of highly oriented pyrolytic graphite (HOPG), diamond (111) and heteroepitaxial fullerite films on mica in the impact energy range between 100 and 1500 eV are studied by mass, energy, and angle resolved time-of-flight mass spectrometry. For the graphite and diamond surfaces, highly inelastic scattering has been observed. The analysis of the velocity dependence of the scattered ions reveals that the normal and tangential component of the ion velocity have different significance for the collision dynamics. The normal component of the velocity appears to determine the amount of energy transferred into vibrational and deformational energy of the projectile and target. The final kinetic energy is independent of the impact energy for impact angles of ≈20° and impact energies between 140 and 450 eV. This observation can be explained by the existence of an upper bound of the final kinetic energy that is defined by the amount of energy stored in the deformed molecule without being deposited or destroyed. The tangential component is partially transformed into rotational energy of the [Formula: see text] in the collision with the surface, as may be explained by a simple rolling ball model.

In contrast, scattering from heteroepitaxial fullerite films is nearly elastic for impact energies up to 230 eV and impact angles of about 20°. Additionally, the velocity distributions reveal a low velocity component. Its relative intensity increases with increasing impact energy and remains the only feature in the velocity distribution for impact energies higher than 290 eV. This component is due to sputtering of surface molecules. The angular dependent intensities of the fast ions exhibit a rich structure. This can be attributed to rainbow scattering, as confirmed by classical trajectory and molecular dynamics calculations with different levels of sophistication. These calculations also show that linear collision sequences along the closed packed rows of the fullerite surface may be generated as the result of the [Formula: see text] impact. A detailed study of these collision sequences by molecular dynamics calculations reveals that rainbow effects might be possible when these sequences are defocused due to thermal motion of the surface molecules. The contribution of this process to the measured velocity and angular distributions is discussed.
ESTIMATION OF THE EFFECTIVE DIELECTRIC RESPONSE FROM HOPPING ACTIVATION ENERGY IN THE VICINITY OF INSULATOR-METAL TRANSITION IN SEMICONDUCTORS
Authors: ABBOUDY S.
Published: October 2004

The effect of the energy overlap integral, due to the partial overlap of the adjacent wave functions of impurities, on the dielectric response ε of n-type semiconductor is examined. The proposed model suggests that ε diverges as the overlap increases, i.e. as the impurity concentration n is increased and essentially goes to a non-vanishing value as n approaches a critical value nc, defining the insulator-metal transition. It also predicts that ε→k (the host material dielectric constant) when n becomes low enough such that the impurity contribution to ε is negligibly small.
RESONANCE SCATTERING OF HIGH ENERGY ELECTRONS BY A CRYSTAL SURFACE
Authors: DUDAREV S.L. , WHELAN M.J.
Published: October 2004

In this review we summarize the results of recent experimental and theoretical studies of the phenomenon known as resonance scattering of high-energy electrons from crystal surfaces. Resonance scattering is responsible for the appearance of bright features observed in reflection high-energy electron diffraction (RHEED) patterns and has found numerous applications in reflection electron microscopy and in RHEED studies of dynamics of molecular beam epitaxial growth of semiconductor crystals. The origin of the effect remained obscure for more than sixty years following the discovery of resonance scattering by Kikuchi and Nakagawa in 1933. Below we review theoretical models of the phenomenon which have been developed recently and which have provided the basis for understanding of the mechanism of resonance scattering. We conclude the review with a list of presently unsolved problems which, as we hope, can stimulate future progress in the theory of RHEED.
DETERMINATION OF THE ELASTIC CONSTANTS OF ANISOTROPIC SOLIDS FROM GROUP VELOCITIES MEASURED IN SYMMETRY DIRECTIONS
Authors: KIM KWANG YUL , EVERY ARTHUR G. , SACHSE WOLFGANG
Published: October 2004

We present in this article a novel method of determining all three elastic constants of cubic crystals from a single broadband waveform propagating in the [001] direction. The method can be easily extended to media of orthorhombic symmetry whose symmetry plane quasitransverse (QT) group velocity sheet is folded across the symmetry axis. The usefulness of these formulas lies in providing a very convenient and easy method of determining all the elastic constants of a medium from the rays propagating in the principal symmetry directions of the medium. Particular emphasis is given to the so-called oblique-mode QT rays with group velocity lying along a symmetry axis but with wave normal lying away from that axis in a symmetry plane. Through the use of these oblique modes the need to make off-axis measurements to obtain a complete set of elastic constants is circumvented. Moreover, we describe a method of clarifying the ambiguity that arises; with which symmetry plane is the wave normal of an oblique-mode QT ray propagating in the symmetry axis associated. Further, we show how the effect of a finite rise time source can be corrected for in the determination of a mixed index elastic constant.
CHARGE TRANSPORT AND CONDUCTION MECHANISM OF SOME SUBSTITUTED STRONTIUM W-TYPE HEXAGONAL FERRITES
Authors: PURUSHOTHAM Y. , REDDY P. VENUGOPAL
Published: October 2004

The present work is intended to investigate the thermopower and electrical conductivity studies of some substituted strontium W-type hexagonal ferrites as a function of composition and temperature. On the basis of the sign of the Seebeck coefficient (S), the ferrites under investigation have been classified as n-type semiconductors. Using the experimental values of Seebeck coefficient at various temperatures, the values of charge carrier concentration have been determined. On the basis of the temperature variation of charge carrier mobility, the conduction mechanism in these ferrites has been discussed.
JACK POLYNOMIALS AND THE MULTI-COMPONENT CALOGERO-SUTHERLAND MODEL
Authors: FORRESTER P.J.
Published: October 2004

Using the ground state ψ0 of a multi-component generalization of the Calogero-Sutherland model as a weight function, orthogonal polynomials in the coordinates of one of the species are constructed. Using evidence from exact analytic and numerical calculations, it is conjectured that these polynomials are the Jack polynomials [Formula: see text] where λ is the coupling constant. The value of the normalization integral for [Formula: see text] is conjectured, and some further related integrals are evaluated.
SURFACE POLARON WITH A BARRIER POTENTIAL: UPPER BOUND TO THE GROUND-STATE ENERGY
Authors: BOGOLUBOV N.N. , KIREEV A.N.
Published: October 2004

A general variational method is proposed for investigating the surface polaron ground state valid for any coupling strength of an electron-surface-optical-phonon interaction and for any height of a barrier potential at the crystal boundary. The ground states of the surface polaron at the infinitely high barrier potential and of the surface polaron without the barrier potential are considered. The properties of the surface polarons are discussed in comparison with the bulk polaron theory.
HIGHLY CHARGED SUPERFLUID HELIUM CLUSTER BEAM
Authors: LO SHUI-YIN
Published: October 2004

A device is proposed that can produce highly charged superfluid helium clusters, which can be as small as a micron. Each cluster then contains a large number of coherent helium atoms that can be accelerated together.
SPECTRAL ANOMALY AND HIGH TEMPERATURE SUPERCONDUCTORS
Authors: YIN LAN , CHAKRAVARTY SUDIP
Published: October 2004

Spectral anomaly for interacting fermions is characterized by the spectral function A ([k − k F ], ω) satisfying the scaling relation A (Λy1 [k − k F ], Λy2 ω) =ΛyA A ([k − k F ], ω), where y1, y2, and yA are the exponents defining the universality class. For a Fermi liquid y1 = 1, y2 = 1, yA = −1; all other values of the exponents are termed anomalous. In this paper, an example for which y1 = 1, y2 = 1, but yA = α − 1 is considered in detail. Attractive interaction added to such a critical system leads to a novel superconducting state, which is explored and its relevance to high temperature cuprate superconductors is discussed.
PHYSICAL PROPERTIES OF METALS FROM A RENORMALIZATION GROUP STANDPOINT
Authors: NAYAK CHETAN , WILCZEK FRANK
Published: October 2004

We derive the equilibrium and transport properties of metals using renormalization group equations and finite-size scaling. Particular attention is given to the well-known cases of Fermi and Luttinger liquids. An important subtlety is that the temperature dependence of many transport coefficients is determined by "dangerous" irrelevant operators. We also characterize violations of Fermi or Luttinger liquid behavior in terms of indices, analogous to the critical indices describing phase transitions. We briefly consider the normal-state properties of the cuprates from this standpoint.
COMPUTER SIMULATION STUDY OF LATTICE SPIN MODELS IN ONE DIMENSION WITH LONG-RANGE INHOMOGENEOUS INTERACTIONS POSSESSING O(2) SYMMETRY
Authors: ROMANO S.
Published: October 2004

We have considered a classical spin system, consisting of n-component unit vectors (n = 2, 3), associated with a semi-infinite lattice in one dimension {uk, k ∈ N+}, and interacting via inhomogeneous pair potentials, in general anisotropic in spin space, and of the long-range ferromagnetic form [Formula: see text] here ∊ is a positive constant setting energy and temperature scales (i.e. T* = k B T/∊), a ≥ 0, b ≥ 0, and the symbols uj, α denote cartesian components of the spins. For some specific values of the two parameters a and b, and on the basis of available theoretical results, one can prove the existence of an ordering transition taking place at finite temperature, and obtain rigorous upper and lower bounds on the transition temperatures. This holds, for example, when n = 2, 3, a > b = 0 (the models studied in our previous paper), as well as for n = 2, a = b > 0 and n = 3, b > a = 0, where a continuous O(2) symmetry of the interaction is involved. We have studied these two latter cases by computer simulation, and made comparison with mean-field treatment; simulation results show a broad qualitative similarity between the four models, and a closer, quantitative one, between pairs of models with the same number of spin components, especially for n = 2.
EFFECTIVE DIPOLE-RADIATION-FIELD THEORY II: ALL ORDERS BEYOND STANDARD COUPLING
Authors: DEKKER H.
Published: October 2004

The novel treatment of the interaction between a charged particle and the electromagnetic field, as presented in paper I [H. Dekker, Int. J. Mod. Phys.B8, 1–19 (1994)], is generalized to all orders beyond the standard dipole model. The resulting nonlinear problem is then again statistically linearized and the ensuing dynamics is solved exactly for a harmonically bound nonrelativistic electron. The earlier noted ultraviolet divergence in the system’s quantum mechanics is found to be absent, unless the bare electron mass were exactly zero. Inter alia it is also found that the electron’s generic quantum distribution is Gaussian.
BROWNIAN MOTION OF SOLITONS IN THE ϕ4MODEL
Authors: ALDABE F.
Published: October 2004

We derive an expression for the correlation function of the random force on a soliton which is consistent with the constraints needed to integrate out the zero modes which appear due to the broken translational symmetry of the soliton solution. It is shown that when the constraint does not commute with the operator which defines the correlation function, i.e. when the operator is not physical, only low frequency phonon contributions may be considered. On the contrary, when the correlation function of the random force on the soliton is constructed with physical operators one may also include in a correct manner the contributions from the optical phonons.
GROUND-STATE DIPOLE-BOUND ANIONS
Authors: DESFRANÇOIS CHARLES , ABDOUL-CARIME HASSAN , SCHERMANN JEAN-PIERRE
Published: October 2004

Ground-state dipole-bound anions are fragile molecular species which excess electrons are almost entirely located in a very diffuse orbital outside the molecular frame. They can be created by attachment of very low energy electrons to polar molecules or small clusters which dipole moments are larger than a practical critical value of 2.5 D. They present analogies with Rydberg atoms and their geometrical structures are nearly identical to those of their neutral parents. Experimentally, dipole-binding of electrons to polar systems is a non-perturbative and reversible ionization process, in contrast with conventional valence-binding. Examples of applications such as mass-spectrometric isomer selection of clusters or determination of electron attachment properties of isolated nucleic acid bases are given.
SUPERCONDUCTING CLASSES IN THE EXTENDED HUBBARD MODEL
Authors: OZAKI MASA-AKI , MIYAI EIJI , KONISHI TOMOAKI , HANAFUSA KAORU
Published: October 2004

This paper describes group theoretical classification of superconducting states (SC) in the extended Hubbard model with on-site repulsion (U), nearest neighbor attraction (V) and nearest neighbour exchange interaction (J) on the two-dimensional square lattice using the mean field approach. By decomposing the pairing interaction into irreducible parts; A1g, B1g and Eu of D4h point symmetry, we have derived two singlet SCs (s-wave and d-wave) from A1g and B1g, eight triplet SCs from Eu. The first three types of triplet SC have pairing by electrons with antiparallel spin, the second two types have pairing by electrons with equal spin and the last three types are non-unitary and have pairing by only up-spin electrons. We showed that three non-unitary states have to be accompanied with a ferromagnetic order from the structure of the maximal little groups. We performed numerical studies for these SCs. For parameters and electron density favorable for the ferromagnetic order, a non-unitary SC coexistent with ferromagnetism is most stable.
FINITE-SIZE CALCULATION OF ANISOTROPIC ANTIFERROMAGNETIC CHAINS AT NONZERO FIELD
Authors: CABRERA G.G. , WEINKETZ S. , MEDEIROS DJALMA
Published: October 2004

The antiferromagnetic spin-1/2 Heisenberg model, with axial anisotropy and applied magnetic field parallel to the axis, is solved numerically by Lanczos diagonalization of finite systems. We devise an extremely accurate method that allows for a reliable extrapolation to the infinite size limit. In the above limit, our results are compared with exact analytical solutions obtained through the Bethe ansatz. As an important example, we probe the behavior of the Critical Magnetic Field in the whole anisotropic region. We find indications that suggest the presence of two different regimes for the scaling of size effects as a function of the anisotropy.
FINITE-TEMPERATURE RENORMALIZATION OF THE (ϕ4)4–MODEL
Authors: VAN EIJCK M.A. , VAN WEERT CH. G.
Published: October 2004

We summarize results of the finite-temperature renormalization group approach, formalized by Matsumoto, Nakano and Umezawa in 1984, for the λ(ϕ4)4-model. The flow parameter is the reference temperature at which the mass parameter and the coupling constant of the theory are defined through renormalization conditions. We derive flow equations to one-loop order, and integrate numerically from zero temperature to above the critical temperature. The mass and the coupling constant both vanish at the critical temperature, and are positive below and above the critical region. In the critical region dimensional reduction to an effective 3D theory takes place. The leading behavior of the mass at high temperature is linear with a small logarithmic sub-leading contribution.
ENERGY-MOMENTUM TENSOR IMPROVEMENTS IN TWO DIMENSIONS
Authors: DESER S. , JACKIW R.
Published: October 2004

We discuss some aspects of the two-dimensional scalar field, considering particularly the action for the conformal anomaly as an “improved” gravitational coupling, and the possibility of introducing a dual coupling, which provides a “chiral” energy-momentum tensor improvement.
CLASSICAL BEHAVIOR IN QUANTUM MECHANICS: A TRANSITION PROBABILITY APPROACH
Authors: LANDSMAN N.P.
Published: October 2004

A formalism is developed for describing approximate classical behavior in finite (but possibly large) quantum systems. This is done in terms of a structure common to classical and quantum mechanics, viz. a Poisson space with a transition probability. Both the limit where ħ→0 in a fixed finite system and the limit where the size of the system goes to infinity are incorporated. In either case, classical behavior is seen only for certain observables and in a restricted class of states.
CHANGE OF INDEPENDENT VARIABLE IN VARIATIONAL PROBLEMS
Authors: EZAWA HIROSHI
Published: October 2004

A change of variables, the dependent as well as the independent, in variational problems is examined to show that it can reduce the associated Euler equation to a simpler form.
OPERATOR METHODS FOR MASTER EQUATIONS IN QUANTUM OPTICS
Authors: SHANTA P. , CHATURVEDI S. , SRINIVASAN V. , KAPOOR A.K.
Published: October 2004

Applications of thermofield dynamics to quantum optics and the lessons one learns for nonequilibrium physics are presented.
A MICROSCOPIC DERIVATION OF STOCHASTIC DIFFERENTIAL EQUATIONS
Authors: ARIMITSU TOSHIHICO
Published: October 2004

With the help of the formulation of Non-Equilibrium Thermo Field Dynamics, constructed is a unified canonical operator formalism for the quantum stochastic differential equations. In the course of its construction, it is found that there are at least two formulations, i.e. one is non-hermitian and the other is hermitian. Having been settled the framework which should be satisfied by the quantum stochastic differential equations, performed is a microscopic derivation of these stochastic differential equations by extending the projector methods. This investigation may open a new field for quantum systems in order to understand the deeper meaning of dissipation.
THERMAL FIELD THEORY IN NON-EQUILIBRIUM STATES
Authors: HENNING P.A. , NAKAMURA K. , YAMANAKA Y.
Published: October 2004

Conventional transport theory is not really applicable to nonequilibrium systems which exhibit strong quantum effects. We present two different approaches to overcome this problem. Firstly we point out how transport equations may be derived that incorporate a nontrivial spectral function as a typical quantum effect, and test this approach in a toy model of a strongly interacting degenerate plasma. Secondly we explore a path to include nonequilibrium effects into quantum field theory through momentum mixing transformations in Fock space. Although the two approaches are completely orthogonal, they lead to the same coherent conclusion.
QUANTUM GROUPS AND THERMO FIELD DYNAMICS
Authors: MARTINO S. DE , SIENA S. DE , VITIELLO G.
Published: October 2004

The algebraic structure of Thermo Field Dynamics for bosons can be fully incorporated in the q-deformation of the Weyl-Heisenberg algebra hq (1) . The doubling of the degrees of freedom, the set of the tilde-conjugation rules, the Bogoliubov transformation and its generator have a direct and simple interpretation in terms of operators and of properties of hq (1) . The notion of “thermal degree of freedom” introduced by Umezawa also finds a more specific formalization since the corresponding “thermal conjugate momentum” can be formally introduced, thus providing us with a set of canonical “thermal” variables.