Fission studies with 140 MeV α\bm{\alpha}-Particles

Binary fission induced by 140 MeV $\alpha$-particles has been measured for $^{\rm nat}$Ag, $^{139}$La, $^{165}$Ho and $^{197}$Au targets. The measured quantities are the total kinetic energies, fragment masses, and fission cross sections. The results are compared with other data and systematics. A minimum of the fission probability in the vicinity $Z^2/A=24$ is observed.Comment: 4 figures, 2 table

Digital diplomacy in GCC countries: strategic communication of Western embassies on Twitter

Drawing upon online communication research, this study identifies six effective communication strategies for social media-based diplomacy on Twitter: interactive, personalized, positive, relevant, and transparent communication among a broad network of stakeholders. By using an extensive mix-method design (i.e., combining a manual content and automated network analyses, N = 4438 tweets), this research examines to what extent these communication strategies are adopted on Twitter by Western embassies active in countries from the Gulf Cooperation Council. We found that embassies are not utilizing social media to its full potential. Although embassies are transparent, use positive sentiment in their online communication and post relevant information to their stakeholders, they hardly engage in direct interactive and personal communication, and only reach out to a limited group of stakeholders. We recommend embassies to put more emphasis on two-way interactive communication with a vast variety of stakeholders

Exploring RNA polymerase regulation by NMR spectroscopy

RNA synthesis is a central process in all organisms, with RNA polymerase (RNAP) as the key enzyme. Multisubunit RNAPs are evolutionary related and are tightly regulated by a multitude of transcription factors. Although Escherichia coli RNAP has been studied extensively, only little information is available about its dynamics and transient interactions. This information, however, are crucial for the complete understanding of transcription regulation in atomic detail. To study RNAP by NMR spectroscopy we developed a highly efficient procedure for the assembly of active RNAP from separately expressed subunits that allows specific labeling of the individual constituents. We recorded [(1)H,(13)C] correlation spectra of isoleucine, leucine, and valine methyl groups of complete RNAP and the separately labeled β’ subunit within reconstituted RNAP. We further produced all RNAP subunits individually, established experiments to determine which RNAP subunit a certain regulator binds to, and identified the β subunit to bind NusE

Modulating between 2e^- and 4e^- pathway in the oxygen reduction reaction with laser-synthesized iron oxide-grafted nitrogen-doped carbon

In this study, we demonstrate the tuning of the oxygen reduction reaction (ORR) by iron/iron oxide nanoparticle grafted laser-patterned nitrogen-doped carbon (LP-NC) electrodes. Depending on the preparation route, i.e. addition of a molecular Fe(NO3)2 precursor before (route 1) or after pre-carbonization (route 2) of the citric acid / urea precursors, either the 4e- or the 2e- pathway in the ORR is facilitated leading to either H2O or H2O2 as a reaction product, respectively. The kinetic reaction conditions afford mixed valence metal oxide nanoparticles embedded in LP-NC in the form of either Fe2O3/Fe or Fe2O3/FeO/Fe, respectively, facilitated by an in situ carbothermal reduction during the laser-induced carbonization. In HR(S)TEM analysis we found evidence for the occurrence of Fe2O3 in the η- or α- phase, depending on the preparation route. Reciprocally, the graphitization is also affected by the preparation route leading to either homogeneous graphitization or locally a graphitized shell structures around the nanoparticles. In the 4e- mediated ORR facilitated by η-Fe2O3/Fe@LP-NC onset potentials as low as 0.70 V (vs. RHE) with a H2O2 production efficiency 4% and 10 % in alkaline and neutral electrolyte, respectively, were determined. On the other hand, α-Fe2O3/FeO/Fe@LP-NC present onset potentials for the 2e- mediated ORR is as low as 0.77 with a H2O2 production efficiency of nearly 80%

Thermotoga maritima NusG : domain interaction mediates autoinhibition and thermostability

NusG, the only universally conserved transcription factor, comprises an N- and a C-terminal domain (NTD, CTD) that are flexibly connected and move independently in Escherichia coli and other organisms. In NusG from the hyperthermophilic bacterium Thermotoga maritima (tmNusG), however, NTD and CTD interact tightly. This closed state stabilizes the CTD, but masks the binding sites for the interaction partners Rho, NusE and RNA polymerase (RNAP), suggesting that tmNusG is autoinhibited. Furthermore, tmNusG and some other bacterial NusGs have an additional domain, DII, of unknown function. Here we demonstrate that tmNusG is indeed autoinhibited and that binding to RNAP may stabilize the open conformation. We identified two interdomain salt bridges as well as Phe336 as major determinants of the domain interaction. By successive weakening of this interaction we show that after domain dissociation tmNusG-CTD can bind to Rho and NusE, similar to the Escherichia coli NusG-CTD, indicating that these interactions are conserved in bacteria. Furthermore, we show that tmNusG-DII interacts with RNAP as well as nucleic acids with a clear preference for double stranded DNA. We suggest that tmNusG-DII supports tmNusG recruitment to the transcription elongation complex and stabilizes the tmNusG:RNAP complex, a necessary adaptation to high temperatures

Inhibition of Ca 2+ channel surface expression by mutant bestrophin‐1 in RPE cells

The BEST1 gene product bestrophin-1, a Ca2+-dependent anion channel, interacts with CaV1.3 Ca2+ channels in the retinal pigment epithelium (RPE). BEST1 mutations lead to Best vitelliform macular dystrophy. A common functional defect of these mutations is reduced trafficking of bestrophin-1 into the plasma membrane. We hypothesized that this defect affects the interaction partner CaV1.3 channel affecting Ca2+ signaling and altered RPE function. Thus, we investigated the protein interaction between CaV1.3 channels and bestrophin-1 by immunoprecipitation, CaV1.3 activity in the presence of mutant bestrophin-1 and intracellular trafficking of the interaction partners in confluent RPE monolayers. We selected four BEST1 mutations, each representing one mutational hotspot of the disease: T6P, F80L, R218C, and F305S. Heterologously expressed L-type channels and mutant bestrophin-1 showed reduced interaction, reduced CaV1.3 channel activity, and changes in surface expression. Transfection of polarized RPE (porcine primary cells, iPSC-RPE) that endogenously express CaV1.3 and wild-type bestrophin-1, with mutant bestrophin-1 confirmed reduction of CaV1.3 surface expression. For the four selected BEST1 mutations, presence of mutant bestrophin-1 led to reduced CaV1.3 activity by modulating pore-function or decreasing surface expression. Reduced CaV1.3 activity might open new ways to understand symptoms of Best vitelliform macular dystrophy such as reduced electro-oculogram, lipofuscin accumulation, and vision impairment