1,721,154 research outputs found
A STUDY ON THE ELECTRIC CONDUCTANCE OF RESISTANCE SPOT WELDS - THE CONTACT CONDUCTANCE BETWEEN 2 THIN PLATES
No full textThe authors thank the anonymous reviewer for his constructive comments on the discussion of the results
Dual-band internal WLAN antenna for 2.4/5 GHz laptop PC applications
No full textThis paper presents a dual-band internal WLAN PIFA for 2.4/5 GHz laptop applications in consideration of the influences of laptop housing and LCD. The prototype antenna is modified when installed along the perimeter of the display panel of the laptop housing. The proposed antenna has a small ground plane and achieves an impedance bandwidth of 250 MHz (2.37-2.62 GHz) in Bluetooth band and 950 MHz (4.98-5.93 GHz) near 5 GHz in WLAN band within 2:1 voltage standing wave ratio (VSWR). It also shows good antenna gain with small volume. These features make it an alternative for use in dual-band WLAN antennas. Design details for the proposed antenna in the case of the antenna itself and the application of laptop PC housing are described, and experimental results of the antenna achievements are investigated and discussed. (c) 2006 Wiley Periodicals, Inc
Crystal structure of the human GINS complex
No full textThe GINS complex mediates the assembly of the MCM2-7 (minichromosome maintenance) complex with proteins in a replisome progression complex. The eukaryotic GINS complex is composed of Sld5, Psf1, Psf2, and Psf3, which must be assembled for cell proliferation. We determined the crystal structure of the human GINS complex: GINS forms an elliptical shape with a small central channel. The structures of Sld5 and Psf2 resemble those of Psf1 and Psf3, respectively. In addition, the N-terminal and C-terminal domains of Sld5/ Psf1 are permuted in Psf2/ Psf3, which suggests that the four proteins have evolved from a common ancestor. Using a structure- based mutational analysis, we identified the functionally critical surface regions of the GINS complex.X113935sciescopu
Structure-based identification of a novel NTPase from Methanococcus jannaschii
No full textAlmost half of the entire set of predicted genomic products from Methanococcus jannaschii are classified as functionally unknown hypothetical proteins. We present a structure-based identification of the biochemical function of a protein with an as yet unknown function from a M. jannaschii gene, Mj0226. The crystal structure of Mj0226 protein determined at 2.2 Angstrom, resolution reveals that the protein is a homodimer and each monomer folds into an elongated alpha/beta structure of a new ford family. Comparisons of Mj0226 protein with protein structures in the database, however, indicate that one part of the protein is homologous to some of the nucleotide-binding proteins. Biochemical analysis shows that Mj0226 protein is a novel nucleotide triphosphatase that can efficiently hydrolyze nonstandard nucleotides such as XTP to XMP or ITP to IMP, but not the standard nucleotides, in the presence of Mg2+ or Mn2+ ions.X11106Nsciescopu
Crystal structure of the Mus81-Eme1 complex
No full textThe Mus81-Eme1 complex is a structure-specific endonuclease that plays an important role in rescuing stalled replication forks and resolving the meiotic recombination intermediates in eukaryotes. We have determined the crystal structure of the Mus81-Eme1 complex. Both Mus81 and Eme1 consist of a central nuclease domain, two repeats of the helix-hairpin-helix (HhH) motif at their C-terminal region, and a linker helix. While each domain structure resembles archaeal XPF homologs, the overall structure is significantly different from those due to the structure of a linker helix. We show that a flexible intradomain linker that formed with 36 residues in the nuclease domain of Eme1 is essential for the recognition of DNA. We identified several basic residues lining the outer surface of the active site cleft of Mus81 that are involved in the interaction with a flexible arm of a nicked Holliday junction (HJ). These interactions might contribute to the optimal positioning of the opposite junction across the nick into the catalytic site, which provided the basis for the "nick and counternick" mechanism of Mus81-Eme1 and for the nicked HJ to be the favored in vitro substrate of this enzyme.X113132sciescopu
Identification of microstructure reaction products in active filler metal/alumina brazement
No full textThe crystal structure of an Fe-superoxide dismutase from the hyperthermophile Aquifex pyrophilus at 1.9 angstrom resolution: Structural basis for thermostability
No full textSuperoxide dismutase (SOD) from Aquifex pyrophilus, a hyperthermophilic bacterium, is an extremely heat-stable enzyme that maintains about 70% of its activity after heat treatment for 60 minutes at 100 degrees C. To understand the molecular basis of thermostability of this enzyme, we have determined the crystal structure of A. pyrophilus superoxide dismutase (Ap SOD), an Fe containing homotetrameric enzyme, at 1.9 Angstrom resolution, and compared it with SOD structures from a mesophile and a thermophile, and other enzyme structures from other hyperthermophiles. The structure has been refined to a crystallographic X-factor (I > 2 sigma) of 17.0% and R-free (I > 2 sigma) of 19.9%. While the overall structure of the Ap SOD monomer is similar to the other SODs, significant conformational differences are observed in a highly variable loop region and the C-terminal helix. The conformational differences in these regions alter the subunit arrangement of this enzyme and generate a very compact tetramer. Structural comparisons of three SODs have revealed that Ap SOD has some stabilizing features at both the tertiary and the quaternary structural level: The Ap SOD monomer contains a large number of ion-pairs and the Ap SOD tetramer has a dramatically increased buried surface area per monomer. Comparisons of the Ap SOD structure with that of other known enzymes from hyperthermophiles reveal that the increased number of intrasubunit ion-pairs is a common feature. (C) 1997 Academic Press Limited.X11107104sciescopu
Crystallization and preliminary X-ray analysis of glutamate racemase from Aquifex pyrophilus, a hyperthermophilic bacterium
No full textGlutamate racemase catalyzes the reversible reaction of L-glutamate to D-glutamate, an essential component of the bacterial cell wall. Glutamate racemase from Aquifex pyrophilus has been crystallized by the hanging-drop vapor-diffusion method using polyethylene glycol 6000 as a precipitant. The crystals belong to space group P6(1)22 or P6(5)22 with unit-cell parameters a = b = 72.1, c = 185.02 Angstrom. The asymmetric unit contains one molecule, corresponding to a V-m value of 2.35 Angstrom(3) Da(-1). Complete data sets from a native and a mercury-derivative crystal have been collected at 2.0 and 2.3 Angstrom resolution, respectively, using a synchrotron-radiation source.X113sciescopu
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