2,173 research outputs found
Deduced Primary Structure of the β Subunit of Brain Type II Ca2+/calmodulin-dependent Protein Kinase Determined by Molecular Cloning
cDNA clones coding for the β subunit of rat brain type II Ca2+/calmodulin-dependent protein kinase were isolated and sequenced. The clones, including one containing the entire coding region, hybridize at high stringency to a single band of poly(A)+ RNA of length 4.8 kilobases. The subunit coded for by the clones was identified by in vitro transcription of the cDNA followed by translation of the resulting RNA. The DNA sequence of the clones contains a single long open reading frame (1626 nucleotides) coding for a protein of 542 amino acids with a molecular weight of 60,333, the amino-terminal half of which is homologous to several other protein kinases. Potential ATP- and calmodulin-binding domains were identified. Two independent clones contain an identical 45-nucleotide deletion, relative to the clones described above, resulting in a shorter open reading frame coding for a protein of molecular weight 58,000. This suggests that the minor, 58-kDa β' subunit of the type II Ca2+/calmodulin-dependent kinase may be synthesized on a separate message
Purification and characterization of a calmodulin-dependent protein kinase that is highly concentrated in brain
A calcium and calmodulin-dependent protein kinase has been purified from rat brain. It was monitored during the purification by its ability to phosphorylate the synaptic vesicle-associated protein, synapsin I. A 300-fold purification was sufficient to produce kinase that is 90-95% pure as determined by scans of stained sodium dodecyl sulfate-polyacrylamide gels and has a specific activity of 2.9 mumol of 32P transferred per min/mg of protein. Thus, the kinase is a relatively abundant brain enzyme, perhaps comprising as much as 0.3% of the total brain protein. The Stokes radius (95 A) and sedimentation coefficient (16.4 S) of the kinase indicate a holoenzyme molecular weight of approximately 650,000. The holoenzyme is composed of three subunits as judged by their co-migration with kinase activity during the purification steps and co-precipitation with kinase activity by a specific anti-kinase monoclonal antibody. The three subunits have molecular weights of 50,000, 58,000, and 60,000, and have been termed alpha, beta', and beta, respectively. The alpha- and beta-subunits are distinct peptides, however, beta' may have been generated from beta by proteolysis. All three of these subunits bind calmodulin in the presence of calcium and are autophosphorylated under conditions in which the kinase is active. The subunits are present in a ratio of about 3 alpha-subunits to 1 beta/beta'-subunit. We therefore postulate that the 650,000-Da holoenzyme consists of approximately 9 alpha-subunits and 3 beta/beta'-subunits. The abundance of this calmodulin-dependent protein kinase indicates that its activation is likely to be an important biochemical response to increases in calcium ion concentration in neuronal tissue
Valuing remnant vegetation in Central Queensland using choice modelling
In the Desert Uplands region of Central Queensland, many pastoralists are clearing vegetation in order to improve cattle grazing production. A choice modelling study was undertaken to provide estimates of the benefits of retaining remnant vegetation that are appropriate for inclusion in a cost benefit analysis of tighter clearing restrictions. Attributes included in the choice model were reductions in the population size of nonâthreatened species, the number of endangered species lost to the region, and changes in regional income and employment. A nested logit model was used to model the data in order to avoid violations of the independence of irrelevant alternatives condition. The estimated benefits are reported for several tree clearing policy regimes that are more stringent than those currently applied.Resource /Energy Economics and Policy,
Quantum secret sharing
Secret sharing is a procedure for splitting a message into several parts so
that no subset of parts is sufficient to read the message, but the entire set
is. We show how this procedure can be implemented using GHZ states. In the
quantum case the presence of an eavesdropper will introduce errors so that his
presence can be detected. We also show how GHZ states can be used to split
quantum information into two parts so that both parts are necessary to
reconstruct the original qubit.Comment: 6 pages, revtex, revised version, to appear in Phys. Rev.
COMPTEL observations of the Virgo blazars 3C 273 and 3C 279
We report the main MeV properties (detections, light curves, spectra) of the Virgo blazars 3C 273 and 3C 279 which were derived from a consistent analysis of all COMPTEL Virgo observations between 1991 and 1997
COMPTEL observations of the blazars 3C 454.3 and CTA 102
We have analyzed the two blazars of 3C 454.3 and CTA 102 using all available COMPTEL data from 1991 to 1999. In the 10â30 MeV band, emission from the general direction of the sources is found at the 4Ď-level, being consistent with contributions from both sources. Below 10 MeV only 3C 454.3 is significantly detected, with the strongest evidence (5.6 Ď) in the 3â10 MeV band. Significant flux variability is not observed for both sources, while a low emission is seen most of the years in the 3â10 MeV light curve for 3C 454.3. Its time-averaged MeV spectrum suggests a power maximum between 3 to 10 MeV
Quantum cryptography with squeezed states
A quantum key distribution scheme based on the use of displaced squeezed
vacuum states is presented. The states are squeezed in one of two field
quadrature components, and the value of the squeezed component is used to
encode a character from an alphabet. The uncertainty relation between
quadrature components prevents an eavesdropper from determining both with
enough precision to determine the character being sent. Losses degrade the
performance of this scheme, but it is possible to use phase-sensitive
amplifiers to boost the signal and partially compensate for their effect.Comment: 15 pages, no figure
Extended Îłâray emission in solar flares
During the solar flare events on 11 and 15 June 1991, COMPTEL measured extended emission in the neutron capture line for about 5 hours after the impulsive phase. The time profiles can be described by a double exponential decay with decay constants on the order of 10 min for the fast and 200 min for the slow component. Within the statistical uncertainty both flares show the same longâterm behaviour. The spectrum during the extended phase is significantly harder than during the impulsive phase and pions are not produced in significant numbers before the beginning of the extended emission. Our results with the measurements of others allow us to rule out longâterm trapping of particles in nonâturbulent loops to explain the extended emission of these two flares and our data favour models based on continued acceleration
Metastatic Squamous Cell Carcinoma in a Northern Brown Bandicoot (<i>Isoodon macrourus</i>)
Aside from a handful of notable exceptions, neoplasia is not reported as a major cause of mortality in wild animal populations and often goes undetected. For northern brown bandicoots specifically, there are few reported tumors in the literature and on file in the Australian Registry of Wildlife Health. This report describes a case of squamous cell carcinoma in a northern brown bandicoot (Isoodon macrourus), with metastases to the draining lymph nodes and lung. This neoplasm consisted predominantly of well-differentiated squamous cells and multifocal keratin pearls, with areas possibly consistent with epithelial to mesenchymal transition, as identified by positive immunohistochemical staining by both pancytokeratin (AE1/AE3) and vimentin. Additional investigations were negative for bandicoot papillomatosis carcinomatosis viruses
Activation in the COMPTEL double-scattering gamma-ray telescope
Abstract-The COMPTEL gamma-ray telescope has been operating in low Earth orbit for six years, since the launch of the Compton Gamma-Ray Observatory in April 1991. Comparisons of data for different orbits and epochs show evidence of activation on time scales from minutes (27Mg, q,2=9.5 min) to years C2Na, q&.58 yr). The activation is correlated with both the orbital altitude and solar cosmic-ray modulation. Because it requires coincident measurements in two different detectors, COMPTEL is most susceptible to instrumental background events in which two or more photons are produced simultaneously
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