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Direct interaction of FliX and FlbD is required for their regulatory activity in Caulobacter crescentus
Background: The temporal and spatial expression of late flagellar genes in Caulobacter crescentus is activated by the transcription factor FlbD and its partner trans-acting factor FliX. The physical interaction of these two proteins represents an alternative mechanism for regulating the activity of transcription factors. This study is to characterize the interaction of the two proteins and the consequences of the interaction on their regulatory activity. Results: FliX and FlbD form stable complexes, which can stand the interference of 2.65 M NaCl. The stability of FliX and FlbD was affected by the co-existence of each other. Five FliX mutants (R71A, L85K, 117-118, T130L, and L136K) were created by site-directed mutagenesis in conserved regions of the protein. All mutants were successfully expressed in both wild-type and Caulobacter strains. All but could rescue the motility and cell division defects of a mutant strain. The ability of FliX to regulate the transcription of class II and class III/IV flagellar promoters was fully diminished due to the L85K mutation. Co-immunoprecipitation experiment revealed that was unable to physically interact with FlbD. Conclusions: FliX interacts with FlbD and thereby directly regulates the activity of FlbD in response to flagellar assembly. Mutations in highly conserved regions of FliX could severely affect the recognition between FliX and FlbD and hence interrupt the normal progression of flagellar synthesis and other developmental events in Caulobacter.Molecular and Cellular Biolog
The effect of post weld heat treatment on the creep behaviour and microstructural evolution in grade 92 steel welds for steam pipe applications
Grade 92 steel has been widely applied in the power generation industry for use as steam pipes,
headers, tubes, etc. owing to a good combination of creep and corrosion resistance. For the
welding of thick section pipes, a multi-pass submerged arc welding process is typically used to
achieve sufficient toughness in the weld. To relieve the internal stress in the welds and to stabilise
their microstructures, a post weld heat treatment (PWHT) is commonly applied. The heat
treatment conditions used for the PWHT have a significant effect on both the resulting
microstructure and the creep behaviour of the welds.
In this study, interrupted creep tests were carried out on two identical Grade 92 welds that had
been given PWHTs at two different temperatures: 732°C and 760°C. It was found that the weld
with the lower PWHT temperature had a significantly reduced stain rate during the creep test. In
addition, microstructural examination of the welds revealed that the primary location of creep
damage was in the heat affected zone in the sample with the lower PWHT temperature, whereas it
was in the weld metal in the sample with the higher PWHT temperature.
To understand the effect of the different PWHT temperatures on the microstructure, initially the
microstructures in the head portions of the two creep test bars were compared. This comparison
was performed quantitatively using a range of electron/ion microscopy based techniques. It was
apparent that in the sample subjected to the higher PWHT temperature, larger Laves phase
particles occurred and increased matrix recovery was observed compared with the sample
subjected to the lower PWHT temperature
Comparing Infrared Dirac-Born-Infeld Brane Inflation to Observations
We compare the Infrared Dirac-Born-Infeld (IR DBI) brane inflation model to
observations using a Bayesian analysis. The current data cannot distinguish it
from the \LambdaCDM model, but is able to give interesting constraints on
various microscopic parameters including the mass of the brane moduli
potential, the fundamental string scale, the charge or warp factor of throats,
and the number of the mobile branes. We quantify some distinctive testable
predictions with stringy signatures, such as the large non-Gaussianity, and the
large, but regional, running of the spectral index. These results illustrate
how we may be able to probe aspects of string theory using cosmological
observations.Comment: 54 pages, 13 figures. v2: non-Gaussianity constraint has been applied
to the model; parameter constraints have tightened significantly, conclusions
unchanged. References added; v3, minor revision, PRD versio
Drosophila OBP LUSH Is Required for Activity of Pheromone-Sensitive Neurons
AbstractOdorant binding proteins (OBPs) are extracellular proteins localized to the chemosensory systems of most terrestrial species. OBPs are expressed by nonneuronal cells and secreted into the fluid bathing olfactory neuron dendrites. Several members have been shown to interact directly with odorants, but the significance of this is not clear. We show that the Drosophila OBP lush is completely devoid of evoked activity to the pheromone 11-cis vaccenyl acetate (VA), revealing that this binding protein is absolutely required for activation of pheromone-sensitive chemosensory neurons. lush mutants are also defective for pheromone-evoked behavior. Importantly, we identify a genetic interaction between lush and spontaneous activity in VA-sensitive neurons in the absence of pheromone. The defects in spontaneous activity and VA sensitivity are reversed by germline transformation with a lush transgene or by introducing recombinant LUSH protein into mutant sensilla. These studies directly link pheromone-induced behavior with OBP-dependent activation of a subset of olfactory neurons
Migration Experience and Premarital Sexual Initiation in Urban Kenya: An Event History Analysis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91327/1/j.1728-4465.2012.00309.x.pd
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