Structural insights into the membrane-extracted dimeric form of the ATPase TraB from the Escherichia coli pKM101 conjugation system

Background: Type IV secretion (T4S) systems are involved in secretion of virulence factors such as toxins or transforming molecules, or bacterial conjugation. T4S systems are composed of 12 proteins named VirB1-B11 and VirD4. Among them, three ATPases are involved in the assembly of the T4S system and/or provide energy for substrate transfer, VirB4, VirB11 and VirD4. The X-ray crystal structures of VirB11 and VirD4 have already been solved but VirB4 has proven to be reluctant to any structural investigation so far. Results: Here, we have used small-angle X-ray scattering to obtain the first structural models for the membrane-extracted, dimeric form of the TraB protein, the VirB4 homolog encoded by the E. coli pKM101 plasmid, and for the monomeric soluble form of the LvhB4 protein, the VirB4 homolog of the T4S system encoded by the Legionella pneumophila lvh operon. We have obtained the low resolution structures of the full-length TraB and of its N- and C-terminal halves. From these SAXS models, we derive the internal organisation of TraB. We also show that the two TraB N- and C-terminal domains are independently involved in the dimerisation of the full-length protein. Conclusions: These models provide the first structural insights into the architecture of VirB4 proteins. In particular, our results highlight the modular arrangement and functional relevance of the dimeric-membrane-bound form of TraB

Analytic evaluation of two-loop renormalization constants of enhanced electroweak strength in the Higgs sector of the Standard Model

We calculate renormalization constants Z_H, Z_w, the Higgs and W-boson mass and tadpole counterterms in the on-mass-shell renormalization scheme to two loops in the heavy-Higgs-boson limit m_H >> M_W. Explicit analytic formulae are presented for the two-loop integrals with masses, which are not known in the literature. As an application, the analytic expression for the two-loop leading correction to the fermionic Higgs boson width is obtained.Comment: 8 pages, 3 Postscript figures, uses epsfig.st

Comments on Density Inversions in Marine Shallow Waters and Beyond

It has been shown within the past 70 years that salinity and thus density inversions are often detectible in shallow bays and estuaries. This terminology means that surface salinities are sometimes higher than those at lower depths. The first such discoveries in this country were made by Sumner, Louderback, Schmitt and Johnston (1914) in San Francisco Bay. They used Negetti-Zambta reversing thermometers for temperature and silver nitrate titration for salinity determination. These were by then considered to be classical methods and had been worked out in northern Europe, mostly in Scandinavia. They were introduced to the United States Gulf Coast and the authors in 1931 by Frank W. Weymouth, of Stanford University, who headed the Shrimp Investigations of the U.S. Bureau of Fisheries from 1930, which were later taken over by Milton J. Lindner

Sudden To Adiabatic Transition in Beta Decay

We discuss effects in beta decays at very low beta energies, of the order of the kinetic energies of atomic electrons. As the beta energy is lowered the atomic response changes from sudden to adiabatic. As a consequence, the beta decay rate increases slightly and the ejection of atomic electrons (shake off) and subsequent production of X rays is turned off. We estimate the transition energy and the change in decay rate. The rate increase is largest in heavy atoms, which have a small Q value in their decay. The X ray switch-off is independent of Q value.Comment: 6 pages LaTe

A Two-Pressure Humidity Generator

A device for precisely humidifying a process gas is presented, with particular application to document preservation. The machine is designed to minimize the risk of damage from overpressure by incorporating multiple safety mechanisms and a simple user interface. The design theory is presented, discussed, and verified. This device is capable of generating humidified gases with relative humidities between 7 and 96 to high accuracy. At conditions suitable for document preservation, the machine is accurate to within 3.5 %, generating a relative humidity of (40 1.4)

A Population of Compact Elliptical Galaxies Detected with the Virtual Observatory

Compact elliptical galaxies are characterized by small sizes and high stellar densities. They are thought to form through tidal stripping of massive progenitors. However, only a handful of them were known, preventing us from understanding the role played by this mechanism in galaxy evolution. We present a population of 21 compact elliptical galaxies gathered with the Virtual Observatory. Follow-up spectroscopy and data mining, using high-resolution images and large databases, show that all the galaxies exhibit old metal-rich stellar populations different from those of dwarf elliptical galaxies of similar masses but similar to those of more massive early-type galaxies, supporting the tidal stripping scenario. Their internal properties are reproduced by numerical simulations, which result in compact dynamically hot remnants resembling the galaxies in our sample.Comment: 26 pages, 5 figures, 2 tables. Science in press, published in Science Express on 1/Oct/2009. Full resolution figures in the supplementary online material are available from the Science Magazine web-sit

Update on the ICUD-SIU consultation on multi-parametric magnetic resonance imaging in localised prostate cancer

Introduction: Prostate cancer (PCa) imaging is a rapidly evolving field. Dramatic improvements in prostate MRI during the last decade will probably change the accuracy of diagnosis. This chapter reviews recent current evidence about MRI diagnostic performance and impact on PCa management. Materials and methods: The International Consultation on Urological Diseases nominated a committee to review the literature on prostate MRI. A search of the PubMed database was conducted to identify articles focussed on MP-MRI detection and staging protocols, reporting and scoring systems, the role of MP-MRI in diagnosing PCa prior to biopsy, in active surveillance, in focal therapy and in detecting local recurrence after treatment. Results: Differences in opinion were reported in the use of the strength of magnets [1.5 Tesla (T) vs. 3T] and coils. More agreement was found regarding the choice of pulse sequences; diffusion-weighted MRI (DW-MRI), dynamic contrast-enhanced MRI (DCE MRI), and/or MR spectroscopy imaging (MRSI) are recommended in addition to conventional T2-weighted anatomical sequences. In 2015, the Prostate Imaging Reporting and Data System (PI-RADS version 2) was described to standardize image acquisition and interpretation. MP-MRI improves detection of clinically significant PCa (csPCa) in the repeat biopsy setting or before the confirmatory biopsy in patients considering active surveillance. It is useful to guide focal treatment and to detect local recurrences after treatment. Its role in biopsy-naive patients or during the course of active surveillance remains debated. Conclusion: MP-MRI is increasingly used to improve detection of csPCa and for the selection of a suitable therapeutic approach

Molecular systematics, phylogeny and biogeography of roaches (Rutilus, Teleostei, Cyprinidae)

The aims of the present study are: (1) to produce a phylogenetic hypothesis for the genus Rutilus by using sequence variation of the entire mitochondrial (mt) cytochrome b (cyt-b) gene. To accomplish this we had sampled a total of 22 populations from the Eastern peri-Mediterranean area and Central Europe. These include 12 species (five of which with multiple populations; Fig. 1 and Table 1) out of the 14 reported in FishBase; (2) to test whether molecular data support the current systematics of the genus; and (3) to produce a biogeographic hypothesis for its diversification based on estimates of divergence times. Results will be discussed in light of the two contrasting biogeographic scenarios available for Southern European primary freshwater fishes