1,333 research outputs found
Streptavidin-Binding Peptide (SBP)-tagged SMC2 allows single-step affinity fluorescence, blotting or purification of the condensin complex
<p>Abstract</p> <p>Background</p> <p>Cell biologists face the need to rapidly analyse their proteins of interest in order to gain insight into their function. Often protein purification, cellular localisation and Western blot analyses can be multi-step processes, where protein is lost, activity is destroyed or effective antibodies have not yet been generated.</p> <p>Aim</p> <p>To develop a method that simplifies the critical protein analytical steps of the laboratory researcher, leading to easy, efficient and rapid protein purification, cellular localisation and quantification.</p> <p>Results</p> <p>We have tagged the SMC2 subunit of the condensin complex with the Streptavidin-Binding Peptide (SBP), optimising and demonstrating the efficacious use of this tag for performing these protein analytical steps. Based on silver staining, and Western analysis, SBP delivered an outstanding specificity and purity of the condensin complex. We also developed a rapid and highly specific procedure to localise SBP-tagged proteins in cells in a single step procedure thus bypassing the need for using antibodies. Furthermore we have shown that the SBP tag can be used for isolating tagged proteins from chemically cross-linked cell populations for capturing DNA-protein interactions.</p> <p>Conclusions</p> <p>The small 38-amino acid synthetic SBP offers the potential to successfully perform all four critical analytical procedures as a single step and should have a general utility for the study of many proteins and protein complexes.</p
Conjugate Hard X-ray Footpoints in the 2003 October 29 X10 Flare: Unshearing Motions, Correlations, and Asymmetries
We present a detailed imaging and spectroscopic study of the conjugate hard
X-ray (HXR) footpoints (FPs) observed with RHESSI in the 2003 October 29 X10
flare. The double FPs first move toward and then away from each other, mainly
parallel and perpendicular to the magnetic neutral line, respectively. The
transition of these two phases of FP unshearing motions coincides with the
direction reversal of the motion of the loop-top (LT) source, and with the
minima of the estimated loop length and LT height. The FPs show temporal
correlations between HXR flux, spectral index, and magnetic field strength. The
HXR flux exponentially correlates with the magnetic field strength, which also
anti-correlates with the spectral index before the second HXR peak's maximum,
suggesting that particle acceleration sensitively depends on the magnetic field
strength and/or reconnection rate. Asymmetries are observed between the FPs: on
average, the eastern FP is 2.2 times brighter in HXR flux and 1.8 times weaker
in magnetic field strength, and moves 2.8 times faster away from the neutral
line than the western FP; the estimated coronal column density to the eastern
FP from the LT source is 1.7 times smaller. The two FPs have marginally
different spectral indexes. The eastern-to-western FP HXR flux ratio and
magnetic field strength ratio are anti-correlated only before the second HXR
peak's maximum. Neither magnetic mirroring nor column density alone can explain
the totality of these observations, but their combination, together with other
transport effects, might provide a full explanation. We have also developed
novel techniques to remove particle contamination from HXR counts and to
estimate effects of pulse pileup in imaging spectroscopy, which can be applied
to other RHESSI flares in similar circumstances.Comment: 22 pages, 14 figures, 4 tables; ApJ 2009, in pres
Evolution of Magnetic Field and Energy in A Major Eruptive Active Region Based on SDO/HMI Observation
We report the evolution of magnetic field and its energy in NOAA active
region 11158 over 5 days based on a vector magnetogram series from the
Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory
(SDO). Fast flux emergence and strong shearing motion led to a quadrupolar
sunspot complex that produced several major eruptions, including the first
X-class flare of Solar Cycle 24. Extrapolated non-linear force-free coronal
fields show substantial electric current and free energy increase during early
flux emergence near a low-lying sigmoidal filament with sheared kilogauss field
in the filament channel. The computed magnetic free energy reaches a maximum of
~2.6e32 erg, about 50% of which is stored below 6 Mm. It decreases by ~0.3e32
erg within 1 hour of the X-class flare, which is likely an underestimation of
the actual energy loss. During the flare, the photospheric field changed
rapidly: horizontal field was enhanced by 28% in the core region, becoming more
inclined and more parallel to the polarity inversion line. Such change is
consistent with the conjectured coronal field "implosion", and is supported by
the coronal loop retraction observed by the Atmospheric Imaging Assembly (AIA).
The extrapolated field becomes more "compact" after the flare, with shorter
loops in the core region, probably because of reconnection. The coronal field
becomes slightly more sheared in the lowest layer, relaxes faster with height,
and is overall less energetic.Comment: Eq. (A1) correcte
Eruptions of Magnetic Ropes in Two Homologous Solar Events on 2002 June 1 and 2: a Key to Understanding of an Enigmatic Flare
The goal of this paper is to understand the drivers, configurations, and
scenarios of two similar eruptive events, which occurred in the same solar
active region 9973 on 2002 June 1 and 2. The June 2 event was previously
studied by Sui, Holman, and Dennis (2006, 2008), who concluded that it was
challenging for popular flare models. Using multi-spectral data, we analyze a
combination of the two events. Each of the events exhibited an evolving
cusp-like feature. We have revealed that these apparent ``cusps'' were most
likely mimicked by twisted magnetic flux ropes, but unlikely to be related to
the inverted Y-like magnetic configuration in the standard flare model. The
ropes originated inside a funnel-like magnetic domain whose base was bounded by
an EUV ring structure, and the top was associated with a coronal null point.
The ropes appear to be the major drivers for the events, but their rise was not
triggered by reconnection in the coronal null point. We propose a scenario and
a three-dimensional scheme for these events in which the filament eruptions and
flares were caused by interaction of the ropes.Comment: 22 pages, 11 figure
Major depression, fibromyalgia and labour force participation: A population-based cross-sectional study
BACKGROUND: Previous studies have documented an elevated frequency of depressive symptoms and disorders in fibromyalgia, but have not examined the association between this comorbidity and occupational status. The purpose of this study was to describe these epidemiological associations using a national probability sample. METHODS: Data from iteration 1.1 of the Canadian Community Health Survey (CCHS) were used. The CCHS 1.1 was a large-scale national general health survey. The prevalence of major depression in subjects reporting that they had been diagnosed with fibromyalgia by a health professional was estimated, and then stratified by demographic variables. Logistic regression models predicting labour force participation were also examined. RESULTS: The annual prevalence of major depression was three times higher in subjects with fibromyalgia: 22.2% (95% CI 19.4 – 24.9), than in those without this condition: 7.2% (95% CI 7.0 – 7.4). The association persisted despite stratification for demographic variables. Logistic regression models predicting labour force participation indicated that both conditions had an independent (negative) effect on labour force participation. CONCLUSION: Fibromyalgia and major depression commonly co-occur and may be related to each other at a pathophysiological level. However, each syndrome is independently and negatively associated with labour force participation. A strength of this study is that it was conducted in a large probability sample from the general population. The main limitations are its cross-sectional nature, and its reliance on self-reported diagnoses of fibromyalgia
On the Brightening Propagation of Post-Flare Loops Observed by TRACE
Examining flare data observed by TRACE satellite from May 1998 to December
2006, we choose 190 (151 M-class and 39 X-class) flare events which display
post-flare loops (PFLs), observed by 171 \AA and 195 \AA wavelengths. 124 of
the 190 events exhibit flare ribbons (FRs), observed by 1600 \AA images. We
investigate the propagation of the brightening of these PFLs along the neutral
lines and the separation of the FRs perpendicular to the neutral lines. In most
of the cases, the length of the FRs ranges from 20 Mm to 170 Mm. The
propagating duration of the brightening is from 10 to 60 minutes, and from 10
minutes to 70 minutes for the separating duration of the FRs. The velocities of
the propagation and the separation range from 3 km/s to 39 km/s and 3 km/s to
15 km/s, respectively. Both of the propagating velocities and the separating
velocities are associated with the flare strength and the length of the FRs. It
appears that the propagation and the separation are dynamically coupled, that
is the greater the propagating velocity is, the faster the separation is.
Furthermore, a greater propagating velocity corresponds to a greater
deceleration (or acceleration). These PFLs display three types of propagating
patterns. Type I propagation, which possesses about half of all the events, is
that the brightening begins at the middle part of a set of PFLs, and propagates
bi-directionally towards its both ends. Type II, possessing 30%, is that the
brightening firstly appears at one end of a set of PFLs, then propagates to the
other end. The remnant belongs to Type III propagation which displays that the
initial brightening takes place at two (or more than two) positions on two (or
more than two) sets of PFLs, and each brightening propagates bi-directionally
along the neutral line.Comment: 13 pages, 11 figures, APJ in pres
High genetic diversity at the extreme range edge: nucleotide variation at nuclear loci in Scots pine (Pinus sylvestris L.) in Scotland
Nucleotide polymorphism at 12 nuclear loci was studied in Scots pine populations across an environmental gradient in Scotland, to evaluate the impacts of demographic history and selection on genetic diversity. At eight loci, diversity patterns were compared between Scottish and continental European populations. At these loci, a similar level of diversity (θsil=~0.01) was found in Scottish vs mainland European populations, contrary to expectations for recent colonization, however, less rapid decay of linkage disequilibrium was observed in the former (ρ=0.0086±0.0009, ρ=0.0245±0.0022, respectively). Scottish populations also showed a deficit of rare nucleotide variants (multi-locus Tajima's D=0.316 vs D=−0.379) and differed significantly from mainland populations in allelic frequency and/or haplotype structure at several loci. Within Scotland, western populations showed slightly reduced nucleotide diversity (πtot=0.0068) compared with those from the south and east (0.0079 and 0.0083, respectively) and about three times higher recombination to diversity ratio (ρ/θ=0.71 vs 0.15 and 0.18, respectively). By comparison with results from coalescent simulations, the observed allelic frequency spectrum in the western populations was compatible with a relatively recent bottleneck (0.00175 × 4Ne generations) that reduced the population to about 2% of the present size. However, heterogeneity in the allelic frequency distribution among geographical regions in Scotland suggests that subsequent admixture of populations with different demographic histories may also have played a role
Dual mobility cup reduces dislocation rate after arthroplasty for femoral neck fracture
<p>Abstract</p> <p>Background</p> <p>Hip dislocation after arthroplasty for femoral neck fractures remains a serious complication. The aim of our study was to investigate the dislocation rate in acute femoral neck fracture patients operated with a posterior approach with cemented conventional or dual articulation acetabular components.</p> <p>Methods</p> <p>We compared the dislocation rate in 56 consecutive patients operated with conventional (single mobility) cemented acetabular components to that in 42 consecutive patients operated with dual articulation acetabular components. All the patients were operated via posterior approach and were followed up to one year postoperatively.</p> <p>Results</p> <p>There were 8 dislocations in the 56 patients having conventional components as compared to no dislocations in those 42 having dual articulation components (p = 0.01). The groups were similar with respect to age and gender distribution.</p> <p>Conclusions</p> <p>We conclude that the use of a cemented dual articulation acetabular component significantly reduces the dislocation rates in femoral neck fracture patients operated via posterior approach.</p
A comparative study of Tam3 and Ac transposition in transgenic tobacco and petunia plants
Transposition of the Anthirrinum majus Tam3 element and the Zea mays Ac element has been monitored in petunia and tobacco plants. Plant vectors were constructed with the transposable elements cloned into the leader sequence of a marker gene. Agrobacterium tumefaciens-mediated leaf disc transformation was used to introduce the transposable element constructs into plant cells. In transgenic plants, excision of the transposable element restores gene expression and results in a clearly distinguishable phenotype. Based on restored expression of the hygromycin phosphotransferase II (HPTII) gene, we established that Tam3 excises in 30% of the transformed petunia plants and in 60% of the transformed tobacco plants. Ac excises from the HPTII gene with comparable frequencies (30%) in both plant species. When the β-glucuronidase (GUS) gene was used to detect transposition of Tam3, a significantly lower excision frequency (13%) was found in both plant species. It could be shown that deletion of parts of the transposable elements Tam3 and Ac, removing either one of the terminal inverted repeats (TIR) or part of the presumptive transposase coding region, abolished the excision from the marker genes. This demonstrates that excision of the transposable element Tam3 in heterologous plant species, as documented for the autonomous element Ac, also depends on both properties. Southern blot hybridization shows the expected excision pattern and the reintegration of Tam3 and Ac elements into the genome of tobacco plants.
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