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  • 1
    Publication Date: 2016-10-08
    Description: Amyloid β (Aβ) peptide is present as a major component in amyloid plaque that is one of the hallmarks of Alzheimer's disease. The peptide contains a single tyrosine residue and Aβ has a major implication in the pathology of the disease progression. Current investigation revealed that the tyrosine side chain attained two different critical stereo orientations in two dissimilar conformational states of the peptide. The extended α-helical structure of the peptide observed in an apolar solvent or methanol/water mixture became disordered in aqueous medium and the radius of gyration decreased. In aqueous medium, the torsional angle around C α –C β of tyrosine group became –60°. However, in its α-helical conformation in an apolar system, the measured angle was 180° and this rotameric state may be reasoned behind stronger tyrosine fluorescence compared with the disordered state of the peptide. Molecular dynamics simulation analyses and spectroscopic studies have helped us to understand the major structural changes in the secondary structure of the peptide in the two conformational states. A conformational clustering indicated that the compact state is more stable with tyrosine residue attaining the torsion angle value of –60°, whereas the native state (in HFIP/water mixture) is prevalent at a torsion angle value of –180°. High solvent accessibility has possibly stabilized the particular rotameric state (–60°) of the tyrosine residue and could be the reason behind decrease in fluorescence of the sole tyrosine residue in an aqueous buffer solution (pH 7.4) compared with its fluorescence in the α-helical structure in the micellar environment.
    Keywords: structural biology, biophysics
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 2
    Oxford University Press
    Publication Date: 2016-10-16
    Description: The eukaryotic translation initiation factor, eIF4G, plays a key functional role in the initiation of cap-dependent translation by acting as an adapter to nucleate the assembly of eIF4F complex. Together with poly(A)-binding protein and eIF3, eIF4F subsequently triggers the recruitment of 43S ribosomal pre-initiation complex to the messenger RNA template. Since eukaryotes primarily regulate translation at the level of initiation, eIF4G is implicated in the control of eukaryotic gene expression. Remarkably, emerging evidence in Saccharomyces cerevisiae indicates that eIF4G also plays a key role in nuclear mRNA biogenesis and surveillance—a finding that is in agreement with its nuclear distribution. Here, we focus on the functional involvement of eIF4G in the nucleus in modulating pre-mRNA splicing, mRNA surveillance and possibly in much-debated nuclear translation. Notably, the nature of the biochemical role of this protein in the major events of cellular mRNA metabolism emphasizes that this crucial protein factor may serve as a general integrator of mRNA functional states by acting as an adapter molecule.
    Print ISSN: 1567-1356
    Electronic ISSN: 1567-1364
    Topics: Biology
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  • 3
    Publication Date: 2012-10-05
    Description: SUMMARY We explore a recently developed procedure for kinematic inversion based on an elliptical subfault approximation. In this method, the slip is modelled by a small set of elliptical patches, each ellipse having a Gaussian distribution of slip. We invert near-field strong ground motion for the 2004 September 28 M w 6.0 Parkfield, California, earthquake. The data set consists of 10 digital three-component 18-s long displacement seismograms. The best model gives a moment of 1.21 × 10 18 N m, with slip on two distinct ellipses, one with a high-slip amplitude of 0.91 m located 20 km northwest of the hypocentre. The average rupture speed of the rupture process is ∼2.7 km s −1 . We find no slip in the top 5 km. At this depth, a lineation of small aftershocks marks the transition from creeping above to locked below, in the interseismic period. The high-slip patch coincides spatially with the hypocentre of the 1966 M w 6.0 Parkfield, California, earthquake. The larger earthquakes prior to the 2004 Parkfield earthquake and the aftershocks of the 2004 earthquake ( M w 〉 3) also lie around this high-slip patch, where our model images a sharp slip gradient. This observation suggests the presence of a permanent asperity that breaks during large earthquakes, and has important implications for the slip deficit observed on the Parkfield segment, which is necessary for reliable seismic hazard assessment.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 4
    Publication Date: 2013-10-08
    Description: We present efficient algorithms for cosmic microwave background (CMB) lensing simulation and power spectrum estimation for flat-sky CMB polarization maps. We build a pure B-mode estimator to remedy E to B leakage due to partial sky coverage. We show that our estimators are unbiased, and consistent with the projected errors. We demonstrate our algorithm using simulated observations of small sky patches with realistic noise and weights for upcoming CMB polarization experiments.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 5
    Publication Date: 2014-04-15
    Description: Poly(ADP-ribose) polymerases (PARP) attach poly(ADP-ribose) (PAR) chains to various proteins including themselves and chromatin. Topoisomerase I (Top1) regulates DNA supercoiling and is the target of camptothecin and indenoisoquinoline anticancer drugs, as it forms Top1 cleavage complexes (Top1cc) that are trapped by the drugs. Endogenous and carcinogenic DNA lesions can also trap Top1cc. Tyrosyl-DNA phosphodiesterase 1 (TDP1), a key repair enzyme for trapped Top1cc, hydrolyzes the phosphodiester bond between the DNA 3'-end and the Top1 tyrosyl moiety. Alternative repair pathways for Top1cc involve endonuclease cleavage. However, it is unknown what determines the choice between TDP1 and the endonuclease repair pathways. Here we show that PARP1 plays a critical role in this process. By generating TDP1 and PARP1 double-knockout lymphoma chicken DT40 cells, we demonstrate that TDP1 and PARP1 are epistatic for the repair of Top1cc. The N-terminal domain of TDP1 directly binds the C-terminal domain of PARP1, and TDP1 is PARylated by PARP1. PARylation stabilizes TDP1 together with SUMOylation of TDP1. TDP1 PARylation enhances its recruitment to DNA damage sites without interfering with TDP1 catalytic activity. TDP1–PARP1 complexes, in turn recruit X-ray repair cross-complementing protein 1 (XRCC1). This work identifies PARP1 as a key component driving the repair of trapped Top1cc by TDP1.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 6
    Publication Date: 2017-06-13
    Description: Black carbon (BC) and other biomass-burning (BB) aerosols are critical components of climate forcing but quantification, predictive climate modeling, and policy decisions have been hampered by limited understanding of the climate drivers of BB and by the lack of long-term records. Prior modeling studies suggested that increased Northern Hemisphere anthropogenic BC emissions increased recent temperatures and regional precipitation, including a northward shift in the Inter-Tropical Convergence Zone (ITCZ). Two Antarctic ice cores were analyzed for BC and the longest record shows that the highest BC deposition during the Holocene occurred ~8-6k years before present in a period of relatively high austral burning season and low growing season insolation. Atmospheric transport modeling suggests South America (SA) as the dominant source of modern Antarctic BC and, consistent with the ice-core record, climate model experiments using mid-Holocene and preindustrial insolation simulate comparable increases in carbon loss due to fires in SA during the mid-Holocene. SA climate proxies document a northward shifted ITCZ and weakened SA Summer Monsoon (SASM) during this period, with associated impacts on hydroclimate and burning. A second Antarctic ice core spanning the last 2.5k years documents similar linkages between hydroclimate and BC, with the lowest deposition during the Little Ice Age characterized by a southerly shifted ITCZ and strengthened SASM. These new results indicate that insolation-driven changes in SA hydroclimate and BB, likely linked to the position of the ITCZ, modulated Antarctic BC deposition during most of the Holocene and suggests connections and feedbacks between future BC emissions and hydroclimate.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
    Publication Date: 2018-07-15
    Description: A nickel-based superalloys sheet finds its applications in many industries. Laser cutting of these alloy sheets are very important from the quality point of view. Thus, it is important to have an optimal combination of parameters in order to achieve quality responses. Keeping this in view, grey relation analysis (GRA) aided with fuzzy logic is applied for multi-objective optimization of Nd:YAG laser beam cutting (LBC) of nickel-based superalloy (SUPERNI 718) sheet. The input parameters considered for this process are assist gas pressure, pulse width, pulse frequency, and cutting speed to optimize response parameters considered as kerf width, kerf deviation and kerf taper. The result found using this approach shows that for optimal response the input parameters need to be set as gas pressure at 2kg/cm 2 , pulse width at 0^s, pulse frequency at 23Hz, and cutting speed at 20mm/min. The optimal parametric mix found using our approach is similar to that found by the previous...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
    Publication Date: 2014-02-28
    Description: Evidence of intense naticid drilling predation occurs on turritelline prey from a turritelline-dominated assemblage (TDA) which lies below the K-T boundary sections in Rajahmundry, India. Previously, it was believed that drilling frequency (DF) on turritelline taxa was low during the Cretaceous. Data from the study area indicates that the Cenozoic level of predation on turritelline taxa already occurred by the Late Cretaceous in the study area. The paleobiogeography of naticid predation is extended from the western world to India, which was located in the southern hemisphere during the Cretaceous. In addition to the high drilling frequency, the Indian fossil record shows that many aspects of naticid behavior; for example, size and site stereotypy, which are characteristic features of Cenozoic predators, were also established by the Late Cretaceous. These data support previous views that the Mesozoic Marine Revolution had minimal influence on morphological change in Late Cretaceous turritelline gastropods and that turritelline gastropods may have developed behavioral and/or physiological antipredatory adaptations. TDAs in general may indicate tremendous fecundity that may act as a buffer against high juvenile mortality due to predation.
    Print ISSN: 0883-1351
    Electronic ISSN: 0883-1351
    Topics: Geosciences
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  • 9
    Publication Date: 2016-11-15
    Description: Author(s): R. Bhattacharjee, S. Samanta, S. Das, S. S. Bhattacharjee, R. Raut, S. S. Ghugre, A. K. Sinha, U. Garg, R. Chakrabarti, S. Mukhopadhyay, A. Dhal, R. P. Singh, N. Madhavan, and S. Muralithar High spin states in Ca 41 have been investigated by using γ -ray spectroscopic techniques following the Al 27 ( O 16 , p n ) Ca 41 fusion-evaporation reaction. Around twelve new transitions belonging to Ca 41 have been observed and placed in the level scheme, which now has been extended up to E x ∼ 9 MeV. The spin-… [Phys. Rev. C 94, 054312] Published Mon Nov 14, 2016
    Keywords: Nuclear Structure
    Print ISSN: 0556-2813
    Electronic ISSN: 1089-490X
    Topics: Physics
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  • 10
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume Le nombre de chromosomes et le caryotype de deux espèces de guêpes du genrePolistes ont été déterminés. Il a été développé une technique comprenant le traitement préalable à la colchicine et au citrate de sodium, lequel permet une identification plus précise des chromosomes. Les espècesPolistes (Aphanilopterus) simillimus avec n=28, 2n=56 chromosomes etPolistes (Aphanilopterus) versicolor versicolor avec n=31, 2n=62 chromosomes ont montré des caryotypes bien caractéristiques.
    Notes: Summary The chromosome number and karyotype of two wasp species of the genusPolistes were determined by a technique involving colchicine and sodium citrate pre-treatment, which permitted a more precise chromosome identification. The speciesPolistes (Aphanilopterus) simillimus, with n=28, 2n=56 chromosomes, andPolistes (Aphanilopterus) versicolor versicolor, with n=31, 2n=62 chromosomes, showed sharply characteristic individual karyotypes.
    Type of Medium: Electronic Resource
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