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  • 1
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    Structure of the Newcastle disease virus hemagglutinin-neuraminidase (HN) ectodomain reveals a four-helix bundle stalk [Microbiology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-09-07
    Description: The paramyxovirus hemagglutinin-neuraminidase (HN) protein plays multiple roles in viral entry and egress, including binding to sialic acid receptors, activating the fusion (F) protein to activate membrane fusion and viral entry, and cleaving sialic acid from carbohydrate chains. HN is an oligomeric integral membrane protein consisting of an N-terminal transmembrane domain, a stalk region, and an enzymatically active neuraminidase (NA) domain. Structures of the HN NA domains have been solved previously; however, the structure of the stalk region has remained elusive. The stalk region contains specificity determinants for F interactions and activation, underlying the requirement for homotypic F and HN interactions in viral entry. Mutations of the Newcastle disease virus HN stalk region have been shown to affect both F activation and NA activities, but a structural basis for understanding these dual affects on HN functions has been lacking. Here, we report the structure of the Newcastle disease virus HN ectodomain, revealing dimers of NA domain dimers flanking the N-terminal stalk domain. The stalk forms a parallel tetrameric coiled-coil bundle (4HB) that allows classification of extensive mutational data, providing insight into the functional roles of the stalk region. Mutations that affect both F activation and NA activities map predominantly to the 4HB hydrophobic core, whereas mutations that affect only F-protein activation map primarily to the 4HB surface. Two of four NA domains interact with the 4HB stalk, and residues at this interface in both the stalk and NA domain have been implicated in HN function.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 2
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    High rate of HTLV-II infection in seropositive i.v. drug abusers in New Orleans (1989)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1989-04-28
    Description: Confirmed infection with HTLV-II (human T cell leukemia virus type II) has been described only in rare cases. The major limitation to serological diagnosis of HTLV-II has been the difficulty of distinguishing HTLV-II from HTLV-I (human T cell leukemia virus type I) infection, because of substantial cross-reactivity between the viruses. A sensitive modification of the polymerase chain reaction method was used to provide unambiguous molecular evidence that a significant proportion of intravenous drug abusers are infected with HTLV, and the majority of these individuals are infected with HTLV-II rather than HTLV-I. Of 23 individuals confirmed by polymerase chain reaction analysis to be infected with HTLV, 21 were identified to be infected with HTLV-II, and 2 were infected with HTLV-I. Molecular identification of an HTLV-II--infected population provides an opportunity to investigate the pathogenicity of HTLV-II in humans.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lee, H -- Swanson, P -- Shorty, V S -- Zack, J A -- Rosenblatt, J D -- Chen, I S -- New York, N.Y. -- Science. 1989 Apr 28;244(4903):471-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Diagnostics Division, Abbott Laboratories, North Chicago, IL 60064.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2655084" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; DNA, Viral/analysis ; DNA-Directed DNA Polymerase ; Genes, Viral ; HTLV-I Antibodies/analysis ; HTLV-I Infections/diagnosis/epidemiology/etiology ; HTLV-II Antibodies/*analysis ; HTLV-II Infections/diagnosis/*epidemiology/etiology ; Human T-lymphotropic virus 1/genetics/immunology ; Human T-lymphotropic virus 2/genetics/immunology ; Humans ; Immunoblotting ; Immunoenzyme Techniques ; Louisiana ; Molecular Sequence Data ; Sequence Homology, Nucleic Acid ; Substance-Related Disorders/*complications
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Reproduction and Immunity-Driven Natural Selection in the Human WFDC Locus (2013)
    Oxford University Press
    Details
    Publication Date: 2013-03-21
    Description: The whey acidic protein (WAP) four-disulfide core domain ( WFDC ) locus located on human chromosome 20q13 spans 19 genes with WAP and/or Kunitz domains. These genes participate in antimicrobial, immune, and tissue homoeostasis activities. Neighboring SEMG genes encode seminal proteins Semenogelin 1 and 2 (SEMG1 and SEMG2). WFDC and SEMG genes have a strikingly high rate of amino acid replacement ( d N / d S ) , indicative of responses to adaptive pressures during vertebrate evolution. To better understand the selection pressures acting on WFDC genes in human populations, we resequenced 18 genes and 54 noncoding segments in 71 European (CEU), African (YRI), and Asian (CHB + JPT) individuals. Overall, we identified 484 single-nucleotide polymorphisms (SNPs), including 65 coding variants (of which 49 are nonsynonymous differences). Using classic neutrality tests, we confirmed the signature of short-term balancing selection on WFDC8 in Europeans and a signature of positive selection spanning genes PI3 , SEMG1, SEMG2, and SLPI. Associated with the latter signal, we identified an unusually homogeneous-derived 100-kb haplotype with a frequency of 88% in Asian populations. A putative candidate variant targeted by selection is Thr56Ser in SEMG1 , which may alter the proteolytic profile of SEMG1 and antimicrobial activities of semen. All the well-characterized genes residing in the WDFC locus encode proteins that appear to have a role in immunity and/or fertility, two processes that are often associated with adaptive evolution. This study provides further evidence that the WFDC and SEMG loci have been under strong adaptive pressure within the short timescale of modern humans.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 4
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    Identification of Genes in Saccharomyces cerevisiae that Are Haploinsufficient for Overcoming Amino Acid Starvation (2017)
    Genetics Society of America (GSA)
    Details
    Publication Date: 2017-04-14
    Description: The yeast Saccharomyces cerevisiae responds to amino acid deprivation by activating a pathway conserved in eukaryotes to overcome the starvation stress. We have screened the entire yeast heterozygous deletion collection to identify strains haploinsufficient for growth in the presence of sulfometuron methyl, which causes starvation for isoleucine and valine. We have discovered that cells devoid of MET15 are sensitive to sulfometuron methyl, and loss of heterozygosity at the MET15 locus can complicate screening the heterozygous deletion collection. We identified 138 cases of loss of heterozygosity in this screen. After eliminating the issues of the MET15 loss of heterozygosity, strains isolated from the collection were retested on sulfometuron methyl. To determine the general effect of the mutations for a starvation response, SMM-sensitive strains were tested for the ability to grow in the presence of canavanine, which induces arginine starvation, and strains that were MET15 were also tested for growth in the presence of ethionine, which causes methionine starvation. Many of the genes identified in our study were not previously identified as starvation-responsive genes, including a number of essential genes that are not easily screened in a systematic way. The genes identified span a broad range of biological functions, including many involved in some level of gene expression. Several unnamed proteins have also been identified, giving a clue as to possible functions of the encoded proteins.
    Electronic ISSN: 2160-1836
    Topics: Biology
    Published by Genetics Society of America (GSA)
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  • 5
    Electronic Resource
    Electronic Resource
    Mining-induced seismicity in faulted geologic structures: An analysis of seismicity-induced slip potential (1992)
    Springer
    Pure and applied geophysics 139 (1992), S. 657-676 
    Details
    ISSN: 1420-9136
    Keywords: Mining-induced seismicity ; slip potential ; fault-slip ; rock bursts ; stress interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Relationships between the locations of mining-induced seismic events, local fault structure, and mine geometry were examined in a deep hard-rock mine in northern Idaho. Stopes experiencing rock bursts and other large seismic events were found to fall into two structural regimes: the “Silver Vein”, and the “N48°W Trend,” a steeply dipping plane of seismic activity that is subparallel to major local steeply dipping faults which bound blocky structures. The N48°W Trend also intersects a shaft that was seriously damaged when fault gouge was expelled into the opening during a 3-month period of high seismic energy release. Models of stress interaction are used to support the hypothesis that mining-induced deformation was mobilized along a 1.5 km length of the N48°W Trend. Specifically, numerical models are used to simulate rupture of seismic events and estimate induced changes in the quasi-static stress field. A Coulomb failure criterion is used with these results to estimate the spatial variation in potential for slip on planes parallel to local faulting. Increases in the potential for slip on fault planes subparallel to the N48°W Trend are consistent with activation of deformation along its 1.5 km length. For events with constant seismic moment, stress drop is shown to be far more important than source dimension in elevating slip potential along the observed plane of seismic activity
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879957
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  • 6
    Electronic Resource
    Electronic Resource
    Mining-induced microseismic event location errors: Accuracy and precision of two location systems (1992)
    Springer
    Pure and applied geophysics 139 (1992), S. 375-404 
    Details
    ISSN: 1420-9136
    Keywords: Microseismic location ; location accuracy ; location precision ; error analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The accuracy and precision of microseismic event locations were measured, analyzed, and compared for two types of location systems: “anolog” and “digital”. In the first system, relative times of first arrival were estimated from analog signals using automated hardware circuitry; station positions were estimated from mine map coordinates; and event locations were determined using the BLD (Blake, Leighton, and Duvall) direct solution method. In the second system, arrival times were manually measured during interactive displays of digital waveforms; station coordinates were surveyed; and the SW-GBM (Salamon and Wiebols; Godson, Bridges, and McKavanagh) direct basis function was used to solve for locations. Both systems assume constant isotropic seismic velocity of slightly different signals data sets, calibration blast signals with known source site and origin time, and microseismic event signals, were recorded by each location system employing the same array of high-frequency (5 kHz) accelerometers with 150 m maximum dimension. The calibration blast tests indicated a location precision of ±2 m and accuracy of ±10 m for the analog system. Location precision and accuracy for the digital system measured ±1 m and ±8 m, respectively. Numerical experiments were used to assess the contributions of errors in velocity, arrival times, and station positions on the location accuracy and precision for each system. Measured and estimated errors appropriate to each system for microseismic events were simulated in computing source locations for comparison with exact synthetic event locations. Discrepancy vectors between exact locations and locations calculated with known data errors averaged 7.7 and 1.4 m for the analog and digital systems, respectively. These averages are probably more representative of the location precision of microseismic events, since the calibration blast tests produce impulsive seismic arrivals resulting in smaller arrival-time pick errors in the analog system. For both systems, location accuracy is limited by inadequate modeling of the velocity structure. Consequently, when isotropic velocity models are used in the travel-time inversions, the increased effort expended with the digital location system does not, for the particular systems studied, result in increased accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879943
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  • 7
    Electronic Resource
    Electronic Resource
    36 GHz Travelling Wave Maser (1968)
    [s.l.] : Nature Publishing Group
    Nature 218 (1968), S. 158-158 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] All four Zeeman energy levels of Cr+3 are used. In the pushpull pumping scheme the pump frequency is applied to the 13 transition and the 24 transition which are arranged to have the same energy. This overpopulates level 3 and depopulates level 2, producing the population inversion necessary for ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/218158a0
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  • 8
    Electronic Resource
    Electronic Resource
    Electroabsorption in single quantum well GaAs laser structures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1716-1718 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electric field dependent spectral properties of a GaAs graded barrier quantum well heterostructure laser are measured for the first time. Data are presented which show that the electroabsorption below the band gap is due to states in the confinement layers which are perturbed by the quantum well under high field conditions. This effect, which is intermediary between the quantum confined Stark effect and bulk Franz–Keldysh effect, should be present in all quantum well systems with shallow wells in short, high field depletion regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101291
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  • 9
    Electronic Resource
    Electronic Resource
    Scaling and multifractal properties of mixing in chaotic flows (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1439-1456 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mixing (stretching and folding of fluid elements) in chaotic flows is an iterative process generating presumably self-similar distributions of stretching and striation thickness. This hypothesis is investigated using scaling and multifractal techniques for two prototypical time-periodic chaotic flows: one containing no detectable islands (egg-beater flow), the other involving sizable islands as well as no-slip boundaries (flow between eccentric cylinders). The simplest picture arises in the egg-beater flow. Stretching is well described by multifractal scaling if the very high tail of the distribution of stretchings is neglected. Different methods for obtaining the spectrum of fractal dimensions f(α) agree reasonably well, producing a time-independent self-similar distribution. On the other hand, in the flow between eccentric cylinders, the negative moments do not scale, and the spectrum f(α) is time-dependent (and therefore, it is not self-similar). Due to the extremely wide range of values of stretching, a very large number of points needs to be considered in order to characterize mixing in chaotic systems using a multifractal formalism; this suggests that more work is needed in order to understand finite-size effects and how asymptotic states are reached. However, for cases where multifractal scaling applies, it is possible to relate coarse-grained variables (e.g., intermaterial area density) to microscopic features of the flow (e.g., finite-time Lyapunov exponents).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858419
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  • 10
    Electronic Resource
    Electronic Resource
    The statistics of stretching and stirring in chaotic flows (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 822-834 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The statistics of stretching and stirring in time-periodic chaotic flows is studied numerically by following the evolution of stretching of O(105) points. The ratio between stretchings accumulated by each point at successive periods is referred to as a multiplier, and the total stretching is the product of multipliers. As expected, the mean stretching of the population increases exponentially whereas the probability density function of multipliers converges—in just two periods or so—to a time-invariant distribution. There is, however, a considerable degree of order in the spatial distribution of stretching in spite of conditions of global chaos. The self-correlation of multipliers shows as well considerable structure and often there are segregated populations of points: the largest population consists of points that experience extensive stretching, efficient stirring, and have a distribution of stretching values that evolves asymptotically—in about ten periods—into a limiting time-invariant scaling distribution. The remaining points experience slow stretching and, although they also exhibit scaling behavior, are effectively segregated from the rest of the system in the time scale of our simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858013
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