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951.
A method of planning and designing product sorting systems in warehousing is described. The theoretical background of the analytical models and simulation modelling is given. A calculation of the capacity of elements for joining and dividing for different priorities of material flow is described. New parameters are introduced in the formula for calculating the average number of unit loads in a system for joining, in the direction of the slave flow and for a simple analytical model for joining material flows with two different priorities with an exponential distribution of inter-arrival time. Simulation results are obtained using the GPSS/FON simulation language. Some characteristic results, used in the process of planning and design of two new distribution centres in Belgrade, are shown. 相似文献
952.
CY Chiu RB Cary DJ Chen SR Peterson PL Stewart 《Canadian Metallurgical Quarterly》1998,284(4):1075-1081
The DNA-dependent protein kinase (DNA-PK) plays an important role in mammalian DNA double-strand break repair and immunoglobulin gene rearrangement. The DNA-PK holoenzyme is activated by assembly at DNA ends and is comprised of DNA-PKcs, a 460 kDa protein kinase catalytic subunit, and Ku, a 70 kDa/80 kDa heterodimeric DNA-targeting component. We have solved the three-dimensional structure of DNA-PKcs to approximately 21 A resolution by analytically combining images of nearly 9500 individual particles extracted from cryo-electron micrographs. The DNA-PKcs protein has an open, pseudo 2-fold symmetric structure with a gap separating a crown-shaped top from a rounded base. Columns of density are observed to protrude into the gap from both the crown and the base. Measurements of the enclosed volume indicate that the interior of the protein is largely hollow. The structure of DNA-PKcs suggests that its association with DNA may involve the internalization of double-stranded ends. 相似文献
953.
954.
Salminen TA; Smith DJ; Jalkanen S; Johnson MS 《Protein engineering, design & selection : PEDS》1998,11(12):1195-1204
Human vascular adhesion protein-1 (HVAP-1) is a multifunctional protein
having at least two different cellular roles, functioning both as a
lymphocyte-endothelial cell adhesion protein and as an enzyme with
monoamine oxidase activity. HVAP-1 is a 180 kDa homodimeric glycoprotein
consisting of a membrane-spanning domain and three predicted extracellular
copper-containing amine oxidase domains. In HVAP-1 the extracellular
domains are composed of a large domain D4, containing the active site and
forming the interface of the dimer, while the smaller D2 and D3 domains
surround the D4 dimer near the entrance to the active site. The structural
model of the catalytic D4 domain of HVAP-1 reveals that all components
necessary for enzymatic monoamine oxidase activity are indeed present
within the HVAP-1 and pinpoints residues that may be key to substrate entry
through a channel to the active site and residues likely to be involved in
substrate specificity as well as structural features critical to dimer
formation. Proper glycosylation is required for the cell adhesion function
of HVAP- 1 and the predicted location of the sugar units at the
solvent-exposed surface suits this function well.
相似文献
955.
Structural studies on an inhibitory antibody against Thermus aquaticus DNA polymerase suggest mode of inhibition 总被引:1,自引:0,他引:1
Murali R; Helmer-Citterich M; Sharkey DJ; Scalice ER; Daiss JL; Sullivan MA; Krishna Murthy HM 《Protein engineering, design & selection : PEDS》1998,11(2):79-86
TP7, an antibody against Thermus aquaticus DNA polymerase I (TaqP), is usedas a thermolabile switch in 'hot start' variations of PCR to minimizenon-specific amplification events. Earlier studies have established thatTP7 binds to the polymerase domain of TaqP, competes with primer templatecomplex for binding and is a potent inhibitor of the polymerase activity ofTaqP. We report crystallographic determination of the structure of an Fabfragment of TP7 and computational docking of the structure with the knownthree-dimensional structure of the enzyme. Our observations stronglysuggest that the origin of inhibitory ability of TP7 is its binding toenzyme residues involved in DNA binding and polymerization mechanism.Although criteria unbiased by extant biochemical data have been used inidentification of a putative solution, the resulting complex offers aneminently plausible structural explanation of biochemical observations. Theresults presented are of general significance for interpretation of dockingexperiments and in design of small molecular inhibitors of TaqP, that arenot structurally similar to substrates, for use in PCR. Structural andfunctional similarities noted among DNA polymerases, and the fact thatseveral DNA polymerases are pharmacological targets, make discovery ofnon-substrate based inhibitors of additional importance. 相似文献
956.
To minimize waste disposal problems associated with the residual radioactivity of the first wall material of a fusion reactor,
fast induced radioactive decay (FIRD) alloys based on the Fe-Cr-Mn system are being investigated. The objective of this research
was to evaluate the effects of irradiation on cyclic strain localization and fatigue crack initiation in a FIRD Fe-12Cr-20Mn
alloy and to compare the response to commercially available 316 stainless steel. The alloys were irradiated with 200 keV Fe
ions to a dose of 1 x 10 ions/cm2 and 15.5 keV He ions to a dose of 7 x 1015 ions/cm2 to simulate the irradiation-induced defect structure and helium concentration that would be produced in a fusion reactor.
Irradiated specimens were fatigued in a cantilever beam fatigue testing machine with the deflection set to produce a fully
reversed total strain amplitude of 0.25% on the surface of the specimen. Acetate replicas were obtained during the fatigue
tests to provide a record of surface fatigue damage. Transmission electron microscopy (TEM) analyses were performed to characterize
the microstructural changes resulting from the irradiations and interactions between fatigue-induced glide dislocations and
the irradiation-induced defects. Results indicate that the irradiated Fe-Cr-Mn alloy exhibits fatigue properties similar to
316 stainless steel. Glide dislocations produced by fatigue cycling annihilate irradiation-induced defects. The defect annihilation
causes the formation of cleared channels in which the cyclic plastic strain is localized. Subsurface slip bands penetrate
the irradiated regions through the cleared channels and serve as fatigue crack initiation sites. 相似文献
957.
JA Hammer DJ O'Shannessy M De Leon R Gould D Zand G Daune RH Quarles 《Canadian Metallurgical Quarterly》1993,35(5):546-558
Mammalian peripheral nervous system (PNS) myelin contains several glycoproteins with molecular weights of 19 to 28 kDa, including the major 28 kDa P0 glycoprotein and a recently cloned protein called PMP-22. Some glycoproteins in this M(r) range in humans, cats and some other mammals react with HNK1, a mouse monoclonal antibody that identifies a carbohydrate epitope shared between the immune system and a number of adhesion proteins in the nervous system. A variety of antibodies to P0, PMP-22, and the carbohydrate determinants reacting with HNK1 were used to characterize immunochemically these 19 to 28 kDa glycoproteins of cat PNS myelin. The HNK1-reactive components include P0 and two slightly smaller 23 to 26 kDa proteins that are immunologically related to P0. However, HNK1 reacts most strongly with a lower molecular weight glycoprotein that does not react with the antibodies to P0 and was identified as PMP-22. Since the carbohydrate structure reacting with HNK1 is generally expressed on adhesion molecules, this result suggests that PMP-22 may function in cell-cell or membrane-membrane interactions. Furthermore, the related human anti-MAG monoclonal IgM antibodies from patients with neuropathy also react strongly with PMP-22, suggesting that it may be a target antigen in the pathogenesis of this disease. Purified PNS and CNS myelin from bony fish (toadfish and trout) were also shown to contain major glycoproteins, in the same 19 to 28 kDa M(r) range, that react very strongly with HNK1. It is shown that fish myelin has major proteins of this size that are immunologically and structurally related to mammalian P0, and it is demonstrated here that one of the strongly HNK1-positive proteins reacted well with an antiserum raised to bovine P0. The presence of high levels of the adhesion-related HNK1 epitope on these major myelin proteins of fish suggests that this carbohydrate structure may have played a role in the molecular evolution of myelin. 相似文献
958.
959.
960.