364 research outputs found
Antibody-based detection of protein phosphorylation status to track the efficacy of novel therapies using nanogram protein quantities from stem cells and cell lines
This protocol describes a highly reproducible antibody-based method that provides protein level and phosphorylation status information from nanogram quantities of protein cell lysate. Nanocapillary isoelectric focusing (cIEF) combines with UV-activated linking chemistry to detect changes in phosphorylation status. As an example application, we describe how to detect changes in response to tyrosine kinase inhibitors (TKIs) in the phosphorylation status of the adaptor protein CrkL, a major substrate of the oncogenic tyrosine kinase BCR-ABL in chronic myeloid leukemia (CML), using highly enriched CML stem cells and mature cell populations in vitro. This protocol provides a 2.5 pg/nl limit of protein detection (<0.2% of a stem cell sample containing <104 cells). Additional assays are described for phosphorylated tyrosine 207 (pTyr207)-CrkL and the protein tyrosine phosphatase PTPRC/CD45; these assays were developed using this protocol and applied to CML patient samples. This method is of high throughput, and it can act as a screen for in vitro cancer stem cell response to drugs and novel agents
ISO observations of a sample of Compact Steep Spectrum and GHz Peaked Spectrum Radio Galaxies
We present results from observations obtained with ISOPHOT, on board the ISO
satellite, of a representative sample of seventeen CSS/GPS radio galaxies and
of a control sample of sixteen extended radio galaxies spanning similar ranges
in redshift (0.2 = 10^26 W/Hz).
The observations have been performed at lambda = 60, 90, 174 and 200 microns.
Seven of the CSS/GPS sources have detections >= 3 sigma at one or more
wavelengths, one of which is detected at >= 5 sigma. By co-adding the data we
have obtained average flux densities at the four wavelengths. We found no
evidence that the FIR luminosities of the CSS/GPS sources are significantly
different from those of the extended objects and therefore there is not any
support for CSS/GPS sources being objects "frustrated" by an abnormally dense
ambient medium. The two samples were then combined, providing FIR information
on a new sample of radio galaxies at intermediate redshifts. We compare this
information with what previously known from IRAS and discuss the average
properties of radio galaxies in the redshift range 0.2 - 0.8. The FIR emission
cannot be accounted for by extrapolation of the synchrotron radio spectrum and
we attribute it to thermal dust emission. The average FIR luminosity is >=
6*10^11 L_sun. Over the observed frequency range the infrared spectrum can be
described by a power law with spectral index alpha >~1.0 +/- 0.2. Assuming the
emission to be due to dust, a range of temperatures is required, from >=80 K to
\~25 K. The dust masses required to explain the FIR emission range from 5*10^5
M_sun for the hotter component up to 2*10^8 M_sun for the colder one.
(abridged)Comment: Astronomy & Astrophysics, in press, 16 pages, 2 Figure
Evidence for Ordered Magnetic Fields in the Quasar Environment
At a distance of 20 pc from the purported supermassive black hole powering
quasars, temperatures and densities are inferred from optical observations to
be ~10**4 K and ~10**4 cm**-3. Here we present Very Long Baseline
Interferometry radio observations revealing organized magnetic fields on the
parsec scale in the hot plasma surrounding the quasar OQ172 (1442+101). These
magnetic fields rotate the plane of polarization of the radio emission coming
from the core and inner jet of the quasar. The derived rotation measure (RM) is
40,000 rad m**-2 in the rest frame of the quasar. Only 10 mas (a projected
distance of 68 pc) from the nucleus the jet absolute values of RM fall to less
than 100 rad m**-2.Comment: in press at ApJ Letters, 12 page LaTeX document includes 4 postscript
figure
Observations of HI Absorbing Gas in Compact Radio Sources at Cosmological Redshifts
We present an overview of the occurrence and properties of atomic gas
associated with compact radio sources at redshifts up to z=0.85. Searches for
HI 21cm absorption were made with the Westerbork Synthesis Radio Telescope at
UHF-high frequencies (725-1200 MHz). Detections were obtained for 19 of the 57
sources with usable spectra (33%). We have found a large range in line depths,
from tau=0.16 to tau<=0.001. There is a substantial variety of line profiles,
including Gaussians of less than 10km/s, to more typically 150km/s, as well as
irregular and multi-peaked absorption profiles, sometimes spanning several
hundred km/s. Assuming uniform coverage of the entire radio source, we obtain
column depths of atomic gas between 1e19 and 3.3e21(Tsp/100K)(1/f)cm^(-2).
There is evidence for significant gas motions, but in contrast to earlier
results at low redshift, there are many sources in which the HI velocity is
substantially negative (up to v=-1420km/s) with respect to the optical
redshift, suggesting that in these sources the atomic gas, rather than falling
into the centre, may be be flowing out, interacting with the jets, or rotating
around the nucleus.Comment: 10 pages, accepted for publication in A&
A Supernova Factory in Mrk 273?
We report on 1.6 and 5.0 GHz observations of the ultraluminous infrared
galaxy (ULIRG) Mrk 273, using the European VLBI Network (EVN) and the
Multi-Element Radio-Linked Interferometer Network (MERLIN). We also make use of
published 1.4 GHz VLBA observations of Mrk 273 by Carilli & Taylor (2000). Our
5 GHz images have a maximum resolution of 5-10 mas, which corresponds to linear
resolutions of 3.5-7 pc at the distance of Mrk 273, and are the most sensitive
high-resolution radio observations yet made of this ULIRG. Component N1, often
pinpointed as a possible AGN, displays a steep spectral index (); hence it is very difficult to reconcile
with N1 being an AGN, and rather suggests that the compact nonthermal radio
emission is produced by an extremely high luminous individual radio supernova
(RSN), or a combination of unresolved emission from nested supernova remnants
(SNR), luminous RSNe, or both. Component N2 is partly resolved out into several
compact radio sources --none of which clearly dominates-- and a region of
extended emission about 30 pc in size. The integrated spectral index of this
region is flat (), which can be interpreted as due to a
superposition of several unresolved components, e.g., RSNe or SNRs, whose radio
emission peaks at different frequencies and is partially free-free absorbed.
The overall extended radio emission from component N is typical of nonthermal,
optically thin radio emission (), and its 1.4 GHz
luminosity ( WHz) is
consistent with being produced by relativistic electrons diffused away from
supernova remnants in an outburst.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society Main Journal. 6 pages, 3 figure
3C459: A highly asymmetric radio galaxy with a starburst
Multifrequency radio observations of the radio galaxy 3C459 using MERLIN, VLA
and the EVN, and an optical HST image using the F702W filter are presented. The
galaxy has a very asymmetric radio structure, a high infrared luminosity and a
young stellar population. The eastern component of the double-lobed structure
is brighter, much closer to the nucleus and is significantly less polarized
than the western one. This is consistent with the jet on the eastern side
interacting with dense gas, which could be due to a merged companion or dense
cloud of gas. The HST image of the galaxy presented here exhibits filamentary
structures, and is compared with the MERLIN 5-GHz radio map. EVN observations
of the prominent central component, which has a steep radio spectrum, show a
strongly curved structure suggesing a bent or helical radio jet. The radio
structure of 3C459 is compared with other highly asymmetric, Fanaroff-Riley II
radio sources, which are also good candidates for studying jet-cloud
interactions. Such sources are usually of small linear size and it is possible
that the jets are interacting with clouds of infalling gas that fuel the radio
source.Comment: 10 pages, 6 figures, 2 table
The puzzling case of the radio-loud QSO 3C 186: a gravitational wave recoiling black hole in a young radio source?
Context. Radio-loud AGNs with powerful relativistic jets are thought to be
associated with rapidly spinning black holes (BHs). BH spin-up may result from
a number of processes, including accretion of matter onto the BH itself, and
catastrophic events such as BH-BH mergers. Aims. We study the intriguing
properties of the powerful (L_bol ~ 10^47 erg s^-1) radio-loud quasar 3C 186.
This object shows peculiar features both in the images and in the spectra.
Methods. We utilize near-IR Hubble Space Telescope (HST) images to study the
properties of the host galaxy, and HST UV and Sloan Digital Sky Survey optical
spectra to study the kinematics of the source. Chandra X-ray data are also used
to better constrain the physical interpretation. Results. HST imaging shows
that the active nucleus is offset by 1.3 +- 0.1 arcsec (i.e. ~11 kpc) with
respect to the center of the host galaxy. Spectroscopic data show that the
broad emission lines are offset by -2140 +-390 km/s with respect to the narrow
lines. Velocity shifts are often seen in QSO spectra, in particular in
high-ionization broad emission lines. The host galaxy of the quasar displays a
distorted morphology with possible tidal features that are typical of the late
stages of a galaxy merger. Conclusions. A number of scenarios can be envisaged
to account for the observed features. While the presence of a peculiar outflow
cannot be completely ruled out, all of the observed features are consistent
with those expected if the QSO is associated with a gravitational wave (GW)
recoiling BH. Future detailed studies of this object will allow us to confirm
this type of scenario and will enable a better understanding of both the
physics of BH-BH mergers and the phenomena associated with the emission of GW
from astrophysical sources.Comment: 16 pages, 8 figures. Accepted for publication in Astronomy &
Astrophysics. New appendix adde
The Compact Structure of Radio-Loud Broad Absorption Line Quasars
We present the results of EVN+MERLIN VLBI polarization observations of 8
Broad Absorption Line (BAL) quasars at 1.6 GHz, including 4 LoBALs and 4 HiBALs
with either steep or flat spectra on VLA scales. Only one steep-spectrum
source, J1122+3124, shows two-sided structure on the scale of 2 kpc. The other
four steep-spectrum sources and three flat-spectrum sources display either an
unresolved image or a core-jet structure on scales of less than three hundred
parsecs. In all cases the marginally resolved core is the dominant radio
component. Linear polarization in the cores has been detected in the range of a
few to 10 percent. Polarization, together with high brightness temperatures
(from 2*10^9-5*10^10 K), suggest a synchrotron origin for the radio emission.
There is no apparent difference in the radio orphologies or polarization
between low-ionization and high-ionization BAL QSOs nor between flat- and
steep-spectrum sources. We discuss the orientation of BAL QSOs with both flat
and steep spectra, and consider a possible evolutionary scenario for BAL QSOs.
In this scenario, BAL QSOs are probably the young population of radio sources,
which are Compact Steep Spectrum or GHz peaked radio source analog at the low
end of radio power.Comment: 16 pages, 3 figures, 4 tables; accepted for publication in MNRA
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