Production of Magnetized Electron Beam from a DC High Voltage Photogun

Bunched-beam electron cooling is a key feature of all proposed designs of the future electron-ion collider, and a requirement for achieving the highest promised collision luminosity. At the Jefferson Lab Electron Ion Collider (JLEIC), fast cooling of ion beams will be accomplished via so-called \u27magnetized cooling\u27 implemented using a recirculator ring that employs an energy recovery linac. In this contribution, we describe the production of magnetized electron beam using a compact 300 kV DC high voltage photogun with an inverted insulator geometry, and using alkali-antimonide photocathodes. Beam magnetization was assessed using a modest diagnostic beamline that includes YAG view screens used to measure the rotation of the electron beamlet passing through a narrow upstream aperture. Magnetization results are presented for different gun bias voltages and for different laser spot sizes at the photocathode, using 532 nm lasers with DC and RF time structure. Photocathode lifetime was measured at currents up to 4.5 mA, with and without beam magnetization

Stem cell function and stress response are controlled by protein synthesis.

Whether protein synthesis and cellular stress response pathways interact to control stem cell function is currently unknown. Here we show that mouse skin stem cells synthesize less protein than their immediate progenitors in vivo, even when forced to proliferate. Our analyses reveal that activation of stress response pathways drives both a global reduction of protein synthesis and altered translational programmes that together promote stem cell functions and tumorigenesis. Mechanistically, we show that inhibition of post-transcriptional cytosine-5 methylation locks tumour-initiating cells in this distinct translational inhibition programme. Paradoxically, this inhibition renders stem cells hypersensitive to cytotoxic stress, as tumour regeneration after treatment with 5-fluorouracil is blocked. Thus, stem cells must revoke translation inhibition pathways to regenerate a tissue or tumour.This work was funded by Cancer Research UK (CR-UK), Worldwide Cancer Research, the Medical Research Council (MRC), the European Research Council (ERC), and EMBO. Research in Michaela Frye's laboratory is supported by a core support grant from the Wellcome Trust and MRC to the Wellcome Trust-Medical Research Cambridge Stem Cell Institute.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nature1828

Corrosion inhibition properties of 1,2,4-Hetrocyclic Systems: Electrochemical, theoretical and Monte Carlo simulation studies

Inhibition of mild steel corrosion in 1N hydrochloric acid with 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one (AMTDT) and (4-amino-4H-1,2,4-triazole-3,5-diyl) dimethanol (ATD) was investigated by polarization (Tafel), electrochemical impedance (EIS), adsorption and computational calculations at 27 °C. The mixed type inhibitor property of these inhibitor molecules was investigated by potentiodynamic polarization studies. It was revealed that the effectiveness of inhibition is influenced by several factors such as the nature and state of the metal surface, the type of corrosive medium, the structure of the chemical compound used as inhibitor and molecular electronic parameters. Obvious correlations were found between corrosion inhibition efficiency and some quantum chemical parameters. Monte Carlo simulations were applied to search for the most stable configuration and adsorption energy for the interaction of inhibitors on Fe (111) interface. Calculated results indicated that the difference in inhibition efficiencies between the compounds can be clearly explained in terms of frontier molecular orbital theory

Human Glutaredoxin 3 Forms [2Fe-2S]-Bridged Complexes with Human BolA2

Human glutaredoxin 3 (Glrx3) is an essential [2Fe-2S]-binding protein with ill-defined roles in immune cell response, embryogenesis, cancer cell growth, and regulation of cardiac hypertrophy. Similar to other members of the CGFS monothiol glutaredoxin (Grx) family, human Glrx3 forms homodimers bridged by two [2Fe-2S] clusters that are ligated by the conserved CGFS motifs and glutathione (GSH). We recently demonstrated that the yeast homologues of human Glrx3 and the yeast BolA-like protein Fra2 form [2Fe-2S]-bridged heterodimers that play a key role in signaling intracellular iron availability. Herein, we provide biophysical and biochemical evidence that the two tandem Grx-like domains in human Glrx3 form similar [2Fe-2S]-bridged complexes with human BolA2. UV–visible absorption and circular dichroism, resonance Raman, and electron paramagnetic resonance spectroscopic analyses of recombinant [2Fe-2S] Glrx3 homodimers and [2Fe-2S] Glrx3–BolA2 complexes indicate that the Fe–S coordination environments in these complexes are virtually identical to those of the analogous complexes in yeast. Furthermore, we demonstrate that apo BolA2 binds to each Grx domain in the [2Fe-2S] Glrx3 homodimer forming a [2Fe-2S] BolA2–Glrx3 heterotrimer. Taken together, these results suggest that the unusual [2Fe-2S]-bridging Grx–BolA interaction is conserved in higher eukaryotes and may play a role in signaling cellular iron status in humans

Monothiol Glutaredoxins and A-Type Proteins: Partners in Fe–S Cluster Trafficking

Monothiol glutaredoxins (Grxs) are proposed to function in Fe-S cluster storage and delivery, based on their ability to exist as apo monomeric forms and dimeric forms containing a subunit-bridging [Fe2S2](2+) cluster, and to accept [Fe2S2](2+) clusters from primary scaffold proteins. In addition yeast cytosolic monothiol Grxs interact with Fra2 (Fe repressor of activation-2), to form a heterodimeric complex with a bound [Fe2S2](2+) cluster that plays a key role in iron sensing and regulation of iron homeostasis. In this work, we report on in vitro UV-visible CD studies of cluster transfer between homodimeric monothiol Grxs and members of the ubiquitous A-type class of Fe-S cluster carrier proteins ((Nif)IscA and SufA). The results reveal rapid, unidirectional, intact and quantitative cluster transfer from the [Fe2S2](2+) cluster-bound forms of A. thaliana GrxS14, S. cerevisiae Grx3, and A. vinelandii Grx-nif homodimers to A. vinelandii (Nif)IscA and from A. thaliana GrxS14 to A. thaliana SufA1. Coupled with in vivo evidence for interaction between monothiol Grxs and A-type Fe-S cluster carrier proteins, the results indicate that these two classes of proteins work together in cellular Fe-S cluster trafficking. However, cluster transfer is reversed in the presence of Fra2, since the [Fe2S2](2+) cluster-bound heterodimeric Grx3-Fra2 complex can be formed by intact [Fe2S2](2+) cluster transfer from (Nif)IscA. The significance of these results for Fe-S cluster biogenesis or repair and the cellular regulation of the Fe-S cluster status are discussed

NSun2-Mediated Cytosine-5 Methylation of Vault Noncoding RNA Determines Its Processing into Regulatory Small RNAs

Autosomal-recessive loss of the NSUN2 gene has been identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNAs), yet the identification of cytosine methylation in other RNA species has been hampered by the lack of sensitive and reliable molecular techniques. Here, we describe miCLIP as an additional approach for identifying RNA methylation sites in transcriptomes. miCLIP is a customized version of the individual-nucleotide-resolution crosslinking and immunoprecipitation (iCLIP) method. We confirm site-specific methylation in tRNAs and additional messenger and noncoding RNAs (ncRNAs). Among these, vault ncRNAs contained six NSun2-methylated cytosines, three of which were confirmed by RNA bisulfite sequencing. Using patient cells lacking the NSun2 protein, we further show that loss of cytosine-5 methylation in vault RNAs causes aberrant processing into Argonaute-associated small RNA fragments that can function as microRNAs. Thus, impaired processing of vault ncRNA may contribute to the etiology of NSun2-deficiency human disorders