10,483 research outputs found
Hsp90-binding immunophilins link p53 to dynein during p53 transport to the nucleus
The tumor suppressor protein p53 is known to be transported to the nucleus along microtubular tracks by cytoplasmic dynein. However, the connection between p53 and the dynein motor protein complex has not been established. Here, we show that hsp90.binding immunophilins link p53.hsp90 complexes to dynein and that prevention of that linkage in vivo inhibits the nuclear movement of p53. First, we show that p53.hsp90 heterocomplexes from DLD-1 human colon cancer cells contain an immunophilin (FKBP52, CyP-40, or PP5) as well as dynein. p53.hsp90.immunophilin.dynein complexes can be formed by incubating immunopurified p53 with rabbit reticulocyte lysate, and we show by peptide competition that the immunophilins link via their tetratricopeptide repeat domains to p53-bound hsp90 and by means of their PPIase domains to the dynein complex. The linkage of immunophilins to the dynein motor is indirect by means of the dynamitin component of the dynein-associated dynactin complex, and we show that purified FKBP52 binds directly by means of its PPIase domain to purified dynamitin. By using a temperature-sensitive mutant of p53 where cytoplasmic-nuclear movement occurs by shift to permissive temperature, we show that p53 movement is impeded when p53 binding to hsp90 is inhibited by the hsp90 inhibitor radicicol. Also, nuclear movement of p53 is inhibited when immunophilin binding to dynein is competed for by expression of a PPIase domain fragment in the same manner as when dynein linkage to cargo is dissociated by expression of dynamitin. This is the first demonstration of the linkage between an hsp90-chaperoned transcription factor and the system for its retrograde movement to the nucleus both in vitro and in vivo.Fil: Galigniana, Mario Daniel. University of Michigan; Estados Unidos. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de QuĂmica BiolĂłgica; ArgentinaFil: Harrell, Jennifer M.. University of Michigan; Estados UnidosFil: O´Hagen, Heather M.. University of Michigan; Estados UnidosFil: Ljungman, Mats. University of Michigan; Estados UnidosFil: Pratt, William B.. University of Michigan; Estados Unido
Optical and ROSAT X-ray observations of the dwarf nova OY Carinae in superoutburst and quiescence
We present ROSAT X-ray and optical light curves of the 1994 February
superoutburst of the eclipsing SU UMa dwarf nova OY Carinae. There is no
eclipse of the flux in the ROSAT HRI light curve. Contemporaneous `wide B' band
optical light curves show extensive superhump activity and dips at superhump
maximum. Eclipse mapping of these optical light curves reveals a disc with a
considerable physical flare, even three days into the superoutburst decline.
We include a later (1994 July) ROSAT PSPC observation of OY Car that allows
us to put constraints on the quiescent X-ray spectrum. We find that while there
is little to choose between OY Car and its fellow high inclination systems with
regard to the temperature of the emitting gas and the emission measure, we have
difficulties reconciling the column density found from our X-ray observation
with the column found in HST UV observations by Horne et al. (1994). The
obvious option is to invoke time variability.Comment: 16 pages, 14 figures, accepted for publication in MNRA
An XMM-Newton observation of the nova-like variable UX UMa: spatially and spectrally resolved two-component X-ray emission
In the optical and ultraviolet regions of the electromagnetic spectrum, UX
Ursae Majoris is a deeply eclipsing cataclysmic variable. However, no soft
X-ray eclipse was detected in ROSAT observations. We have obtained a 38 ksec
XMM-Newton observation to further constrain the origin of the X-rays. The
combination of spectral and timing information allows us to identify two
components in the X-ray emission of the system. The soft component, dominant
below photon energies of 2 keV, can be fitted with a multi-temperature plasma
model and is uneclipsed. The hard component, dominant above 3 keV, can be
fitted with a kT ~ 5 keV plasma model and appears to be deeply eclipsed. We
suggest that the most likely source of the hard X-ray emission in UX UMa, and
other systems in high mass transfer states, is the boundary layer.Comment: To appear in MNRAS Letter
Zipf's law in Nuclear Multifragmentation and Percolation Theory
We investigate the average sizes of the largest fragments in nuclear
multifragmentation events near the critical point of the nuclear matter phase
diagram. We perform analytic calculations employing Poisson statistics as well
as Monte Carlo simulations of the percolation type. We find that previous
claims of manifestations of Zipf's Law in the rank-ordered fragment size
distributions are not born out in our result, neither in finite nor infinite
systems. Instead, we find that Zipf-Mandelbrot distributions are needed to
describe the results, and we show how one can derive them in the infinite size
limit. However, we agree with previous authors that the investigation of
rank-ordered fragment size distributions is an alternative way to look for the
critical point in the nuclear matter diagram.Comment: 8 pages, 11 figures, submitted to PR
Canonical and Microcanonical Distributions for Fermi Systems
Recursion relations are presented that allow exact calculation of canonical
and microcanonical partition functions of degenerate Fermi systems, assuming no
explicit two-body interactions. Calculations of the level density, sorted by
angular momentum, are presented for Ni-56 are presented. The issue of treating
unbound states is also addressed.Comment: 5 pages, 5 figure
Relation between concurrence and Berry phase of an entangled state of two spin 1/2 particles
We have studied here the influence of the Berry phase generated due to a
cyclic evolution of an entangled state of two spin 1/2 particles. It is shown
that the measure of formation of entanglement is related to the cyclic
geometric phase of the individual spins. \\Comment: 6 pages. Accepted in Europhys. Letters (likely to be published in vol
73, pp1-6 (2006)
Brightest Cluster Galaxies and Core Gas Density in REXCESS Clusters
We investigate the relationship between brightest cluster galaxies (BCGs) and
their host clusters using a sample of nearby galaxy clusters from the
Representative XMM Cluster Structure Survey (REXCESS). The sample was imaged
with the Southern Observatory for Astrophysical Research (SOAR) in R band to
investigate the mass of the old stellar population. Using a metric radius of
12h^-1 kpc, we found that the BCG luminosity depends weakly on overall cluster
mass as L_BCG \propto M_cl^0.18+-0.07, consistent with previous work. We found
that 90% of the BCGs are located within 0.035 r_500 of the peak of the X-ray
emission, including all of the cool core (CC) clusters. We also found an
unexpected correlation between the BCG metric luminosity and the core gas
density for non-cool core (non-CC) clusters, following a power law of n_e
\propto L_BCG^2.7+-0.4 (where n_e is measured at 0.008 r_500). The correlation
is not easily explained by star formation (which is weak in non-CC clusters) or
overall cluster mass (which is not correlated with core gas density). The trend
persists even when the BCG is not located near the peak of the X-ray emission,
so proximity is not necessary. We suggest that, for non-CC clusters, this
correlation implies that the same process that sets the central entropy of the
cluster gas also determines the central stellar density of the BCG, and that
this underlying physical process is likely to be mergers.Comment: 16 pages, 8 figures, accepted Astrophysical Journa
Vegetable and fruit intake in Australian adolescents: Trends over time and perceptions of consumption
The consumption of vegetables and fruit during adolescence is crucial to ensuring adequate intake of the nutrients required to meet the rapid growth that characterises this developmental period. However, significant reductions in vegetable and fruit intake during adolescence have been observed making the promotion of consumption an important health promotion challenge. To monitor progress in this population segment toward meeting recommended intake levels and identifying at-risk groups, the present study assessed changes in Australian adolescents’ vegetable and fruit consumption over time and identified the demographic factors associated with meeting recommendations. As individuals who are aware of their diet deficiencies are likely to be more receptive to healthy eating interventions, the present study also assessed adolescents’ perceptions of the adequacy of their vegetable and fruit intake and identified the demographic factors associated with correctly perceiving fruit and vegetable intake to be inadequate. Two cross-sectional samples of Western Australian secondary school students aged 12–17 years were surveyed in 2009–2010 (n = 1501) and 2012–2013 (n = 1406). Only 14% of students at Wave 1 and 13% at Wave 2 met the recommended guidelines for vegetable intake while 68% and 71% met the guidelines for fruit intake. Females had significantly greater odds of failing to meet guidelines for vegetable intake than males. Only 50% of students correctly identified their vegetable and fruit intake to be inadequate. The observed very low levels of compliance with vegetable intake recommendations suggest that addressing deficiencies in vegetable consumption should be a primary focus of future nutrition interventions. Efforts should also be made to increase adolescents’ perceptions of the inadequacy of their intake to optimise the effectiveness of schemes designed to improve vegetable and fruit consumption in this population segment
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