Search

The Fast On-line Reaction Apparatus (FORA) was used to investigate the influence of various reaction parameters onto the formation and transport of metal carbonyl complexes (MCCs) under single-atom chemistry conditions. FORA is based on a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes. Those are recoiling from the spontaneous fission source into a reaction chamber flushed with a gas-mixture containing CO. Upon contact with CO, fission products form volatile MCCs which are further transported by the gas stream to the detection setup, consisting of a charcoal trap mounted in front of a HPGe γ-detector. Depending on the reaction conditions, MCCs are formed and transported with different efficiencies. Using this setup, the impact of varying physical parameters like gas flow, gas pressure, kinetic energy of fission products upon entering the reaction chamber and temperature of the reaction chamber on the formation and transport yields of MCCs was investigated. Using a setup similar to FORA called Miss Piggy, various gas mixtures of CO with a selection of noble gases, as well as N2 and H2, were investigated with respect to their effect onto MCC formation and transport. Based on this measurements, optimized reaction conditions to maximize the synthesis and transport of MCCs are suggested. Explanations for the observed results supported by simulations are suggested as well.

As a step toward licensing a lead–bismuth eutectic (LBE) based reactor design, the adsorption behavior of iodine evaporated from LBE on fused silica was examined. Using inert and reducing carrier gases, depositions with an adsorption enthalpy of − 95 to − 113 kJ mol−1 were observed. These depositions are compatible with a single species, tentatively identified as bismuth monoiodide, BiI. When introducing oxidizing conditions, multiple iodine species with higher volatility form, with adsorption enthalpies ranging from − 67 to − 86 kJ mol−1. Based on an empirical correlation one of these species was identified as monatomic iodine. This work provides fundamental understanding of the LBE/iodine gaseous chemistry and related adsorption deposition behavior.

Accelerator driven fast nuclear reactors cooled by lead-bismuth eutectic (LBE) are developed for transmuting long-lived radionuclides in spent nuclear fuel. Due to the nature of the coolant, operating the reactor will result in a production of 210Po by neutron capture. Understanding the behavior of this highly radiotoxic nuclide in the event of a failure of the window separating the evacuated proton beam guide from the reactor core is required for safety assessments. The present work aims at acquiring this knowledge by studying the evaporation of polonium from neutron-irradiated LBE and its deposition in a scaled down model of the beam tube. Experimental results along with Monte Carlo simulations indicate that polonium adsorbs as a single species with an adsorption enthalpy of approximately −156 kJ/mol.

The evaporation of iodine containing species from tellurium has been investigated together with their adsorption behavior on a fused silica surface. In inert gas, the formation of two species was observed with adsorption enthalpies of around − 90 to − 100 and − 110 to − 120 kJ/mol, respectively. For reducing environments, a single species identified as monatomic iodine was observed with an adsorption enthalpy around − 95 kJ/mol. In oxidizing conditions, species with low adsorption enthalpies ranging from − 65 to − 80 kJ/mol were observed. Presumably, these are iodine oxides as well as oxo-acids of iodine (HIOx). The results of the thermochromatography experiments performed here prove the usefulness of the employed production method for carrier-free iodine isotopes and enhance the understanding of the evaporation and deposition behavior of iodine under various chemical conditions.

In preparation of chemical investigations of the superheavy elements (SHEs) copernicium and flerovium, model experiments with 197Hg were conducted. The interaction of elemental mercury on a sulfur surface was investigated by off-line isothermal gas chromatography. Although the formation of HgS(s) is thermodynamically favored, a strong kinetic hindrance is observed at room temperature, and thus only adsorption interactions could be addressed. A dependence of the adsorption interaction strength on the allotropic transformations of the sulfur surface was observed. The high temperatures needed to promote the chemical interaction of Hg with S prevent sulfur from being a suitable chromatographic surface for SHEs experiments with the state-of-the-art gas phase technology.

The decomposition behavior of group 6 metal hexacarbonyl complexes (M(CO)6) in a tubular flow reactor is simulated. A microscopic Monte-Carlo based model is presented for assessing the first bond dissociation enthalpy of M(CO)6complexes. The suggested approach superimposes a microscopic model of gas adsorption chromatography with a first-order heterogeneous decomposition model. The experimental data on the decomposition of Mo(CO)6and W(CO)6are successfully simulated by introducing available thermodynamic data. Thermodynamic data predicted by relativistic density functional theory is used in our model to deduce the most probable experimental behavior of the corresponding Sg carbonyl complex. Thus, the design of a chemical experiment with Sg(CO)6is suggested, which is sensitive to benchmark our theoretical understanding of the bond stability in carbonyl compounds of the heaviest elements.

Background The favorable decay properties of 43Sc and 44Sc for PET make them promising candidates for future applications in nuclear medicine. An advantage 43Sc (T1/2 = 3.89 h, Eβ+ av = 476 keV [88%]) exhibits over 44Sc, however, is the absence of co-emitted high energy γ-rays. While the production and application of 44Sc has been comprehensively discussed, research concerning 43Sc is still in its infancy. This study aimed at developing two different production routes for 43Sc, based on proton irradiation of enriched 46Ti and 43Ca target material. Results 43Sc was produced via the 46Ti(p,α)43Sc and 43Ca(p,n)43Sc nuclear reactions, yielding activities of up to 225 MBq and 480 MBq, respectively. 43Sc was chemically separated from enriched metallic 46Ti (97.0%) and 43CaCO3 (57.9%) targets, using extraction chromatography. In both cases, ~90% of the final activity was eluted in a small volume of 700 μL, thereby, making it suitable for direct radiolabeling. The prepared products were of high radionuclidic purity, i.e. 98.2% 43Sc were achieved from the irradiation of 46Ti, whereas the product isolated from irradiated 43Ca consisted of 66.2% 43Sc and 33.3% 44Sc. A PET phantom study performed with 43Sc, via both nuclear reactions, revealed slightly improved resolution over 44Sc. In order to assess the chemical purity of the separated 43Sc, radiolabeling experiments were performed with DOTANOC, attaining specific activities of 5–8 MBq/nmol, respectively, with a radiochemical yield of >96%. Conclusions It was determined that higher 43Sc activities were accessible via the 43Ca production route, with a comparatively less complex target preparation and separation procedure. The product isolated from irradiated 46Ti, however, revealed purer 43Sc with minor radionuclidic impurities. Based on the results obtained herein, the 43Ca route features some advantages (such as higher yields and direct usage of the purchased target material) over the 46Ti path when aiming at 43Sc production on a routine basis. Electronic supplementary material The online version of this article (10.1186/s41181-017-0033-9) contains supplementary material, which is available to authorized users.

Rapid in situ formation of metal carbonyl complexes with short-lived nuclides has been demonstrated to be feasible with recoiling ions formed in nuclear fusion and fission reactions. These carbonyl complexes are highly volatile and can be transported rapidly in a gas-stream to counting or chemistry devices. This method was already successfully applied in the chemical investigation of the superheavy element seaborgium (Z = 106) and appears promising for various fields of nuclear research. In this article, we give an overview on the current status of metal carbonyl complex studies with short-lived d-element isotopes.

The adsorption behavior of 197Hg and 183–185Hg on red amorphous selenium (red a-Se) and trigonal selenium (t-Se) was investigated experimentally by off-line and on-line gas chromatographic methods, in preparation of a sensitive chemical separation and characterization of the transactinides copernicium (Cn, Z = 112) and flerovium (Fl, Z = 114). Monte-Carlo simulations of a diffusion controlled deposition were in good agreement with the experimental results, assuming as interaction limits −ΔH ads red a-Se (Hg) > 85 kJ/mol, and −ΔH ads t-Se (Hg)

We report on the in-situ synthesis of metal carbonyl complexes with short-lived isotopes of transition metals. Complexes of molybdenum, technetium, ruthenium and rhodium were synthesized by thermalisation of products of neutron-induced fission of 249Cf in a carbon monoxide-nitrogen mixture. Complexes of tungsten, rhenium, osmium, and iridium were synthesized by thermalizing short-lived isotopes produced in 24Mg-induced fusion evaporation reactions in a carbon monoxide containing atmosphere. The chemical reactions took place at ambient temperature and pressure conditions. The complexes were rapidly transported in a gas stream to collection setups or gas phase chromatography devices. The physisorption of the complexes on Au and SiO2 surfaces was studied. We also studied the stability of some of the complexes, showing that these start to decompose at temperatures above 300 ℃ in contact with a quartz surface. Our studies lay a basis for the investigation of such complexes with transactinides.

Chemical studies of superheavy elements require fast and efficient techniques, due to short half-lives and low production rates of the investigated nuclides. Here, we advocate for using a tubular flow reactor for assessing the thermal stability of the Sg carbonyl complex – Sg(CO)6. The experimental setup was tested with Mo and W carbonyl complexes, as their properties are established and supported by theoretical predictions. The suggested approach proved to be effective in discriminating between the thermal stabilities of Mo(CO)6 and W(CO)6. Therefore, an experimental verification of the predicted Sg–CO bond dissociation energy seems to be feasible by applying this technique. By investigating the effect of 104,105Mo beta-decay on the formation of 104,105Tc carbonyl complex, we estimated the lower reaction time limit for the metal carbonyl synthesis in the gas phase to be more than 100 ms. We examined further the influence of the wall material of the recoil chamber, the carrier gas composition, the gas flow rate, and the pressure on the production yield of 104Mo(CO)6, so that the future stability tests with Sg(CO)6 can be optimized accordingly.

Background Rubella infections are usually characterized by mild self-limiting courses in immunocompetent individuals. However, infections in pregnant women during the first trimester of pregnancy pose a high risk of congenital rubella syndrome possibly resulting in severe defects in the unborn child. Rubella serology of a primary rubella infection is mainly determined by diagnostic confirmation of levels of specific IgM. Study design Here, we report on the performance of the Rubella IgM assay in development on the ARCHITECT instrument, a fully automated high throughput chemiluminescent microparticle immunoassay platform. Sensitivity was examined using commercially available seroconversion panels from vaccinated individuals; specificity was addressed by testing populations of pregnant women, blood donors and hospitalized patients. In addition, the potential for assay interference was evaluated by testing samples of several disease states. As methods of comparison AxSYM, BioMerieux VIDAS and Behring Rubella IgM assays were used. Results The study demonstrates that the ARCHITECT Rubella IgM assay shows improved specificity compared to AxSYM and Behring. Seroconversion sensitivity is equivalent on all assays evaluated. Conclusion Together with high throughput, optimized specificity and suppression of rheumatoid factor (RF) interference the ARCHITECT assay provides a useful improvement for the diagnosis of rubella serology.

Lassa virus is the causative agent of a hemorrhagic fever endemic in west Africa. The RNA genome of Lassa virus encodes the glycoprotein precursor GP-C, a nucleoprotein (NP), the viral polymerase L and a small protein Z (11 kDa). Here, we analyze the role of Z protein for virus maturation. We have recently shown that expression of Z protein in the absence of other viral proteins is sufficient for the release of enveloped Z-containing particles. In this study, we examined particles secreted into the supernatant of a stably Z protein-expressing CHO cell line by electron microscopy. The observed Z-induced virus-like particles did not significantly differ in their morphology and size from Lassa virus particles. Mutation of two proline-rich domains within Z which are known to drastically reduce the release of virus-like particles, had no effect on the cellular localization of the protein nor on its membrane-association. Furthermore, we present evidence that Z interacts with the NP. We assume that Z recruits NP to cellular membranes where virus assembly takes place. We conclude from our data that Lassa virus Z protein plays an essential role in Lassa virus maturation.

Lassa virus glycoprotein C (GP-C) is translated as a precursor (preGP-C) into the lumen of the endoplasmic reticulum (ER) and cotranslationally cleaved into the signal peptide and immature GP-C before GP-C is proteolytically processed into its subunits, GP-1 and GP-2, which form the mature virion spikes. The signal peptide of preGP-C comprises 58 amino acids and contains two distinct hydrophobic domains. Here, we show that each hydrophobic domain alone can insert preGP-C into the ER membrane. Furthermore, we demonstrate that the native signal peptide only uses the N-terminal hydrophobic domain for membrane insertion, exhibiting a novel type of a topology for signal peptides with an extended ER luminal part, which is essential for proteolytic processing of GP-C into GP-1 and GP-2.

Lassa virus is an enveloped virus with glycoprotein spikes on its surface. It contains an RNA ambisense genome that encodes the glycoprotein precursor GP-C, the nucleoprotein NP, the polymerase L, and the Z protein. Here we demonstrate that the Lassa virus Z protein (i) is abundant in viral particles, (ii) is strongly membrane associated, (iii) is sufficient in the absence of all other viral proteins to release enveloped particles, and (iv) contains two late domains, PTAP and PPXY, necessary for the release of virus-like particles. Our data provide evidence that Z is the Lassa virus matrix protein that is the driving force for virus particle release.

Lassa virus glycoprotein is translated as a precursor (pre-GP-C) into the lumen of the endoplasmic reticulum and is cotranslationally cleaved into the signal peptide and GP-C, before GP-C is proteolytically processed into its subunits GP1 and GP2. The signal peptide of pre-GP-C comprises 58 amino acids. The substitution of Lassa virus pre-GP-C signal peptide with another signal peptide still mediates translocation and the release of signal peptide but abolishes the proteolytic cleavage of GP-C into GP1 and GP2. Remarkably, cleavage of GP-C from these hybrid pre-GP-C substrates was restored on coexpression of the wild-type pre-GP-C signal peptide, indicating that the signal peptide functions as a trans-acting factor to promote Lassa virus GP-C processing. To our knowledge, this is the first report on a signal peptide that is essential for proteolytic processing of a secretory pathway protein.

Lassa virus glycoprotein is synthesized as precursor GP-C into the lumen of the endoplasmic reticulum and cleaved posttranslationally into the N-terminal subunit GP-1 and the C-terminal subunit GP-2 by subtilase SKI-1/S1P. The N-terminal portion of the primary translation product preGP-C contains a signal peptide of unknown length. In order to demonstrate the signal peptide cleavage site, purified viral GP-1 isolated from Lassa virus particles was N-terminally sequenced as TSLYKGV, identical to amino acids 59–65 of GP-C. Mutational analysis of the amino acid residues flanking the putative cleavage site led to non-cleavable preGP-C indicating that no other signal peptide cleavage site exists. Interestingly, GP-C mutants with a non-cleavable signal peptide were not further processed by SKI-1/S1P. This observation suggests that the signal peptide cleavage is necessary for GP-C maturation and hence for Lassa virus replication.

The two multiheme c-type cytochromes NrfH and NrfA form a membrane-bound complex that catalyzes menaquinol oxidation by nitrite during respiratory nitrite ammonification of Wolinella succinogenes. Each cysteine residue of the four NrfH heme c binding motifs was individually replaced by serine. Of the resulting eight W. succinogenes mutants, only one is able to grow by nitrite respiration although its electron transport activity from formate to nitrite is decreased. NrfH from this mutant was shown by matrix-assisted laser desorption/ionization mass spectrometry to carry four covalently bound heme groups like wild-type NrfH indicating that the cytochrome c biogenesis system II organism W. succinogenes is able to attach heme to an SXXCH motif.

© Springer International Publishing Switzerland 2015. In this chapter dedicated to the 70th anniversary of Professor Mikhail Grigorievich Itkis the achievements and prospective in the field of the chemistry of superheavy elements are covered wiThemphasis on the results obtained by the collaboration of the Paul Scherrer Institute Villigen Switzerland with the Flerov Laboratory for Nuclear Reactions Dubna Russia. The status of chemical research wiThelements Cn and Flis presented. From the obtained first results interesting scientific questions are deduced and discussed together with some crucial technical developments required to experimentally address these questions in the future.

The electron-transport chain that catalyzes nitrite respiration with formate in Wolinella succinogenes consists of formate dehydrogenase, menaquinone and the nitrite reductase complex. The latter catalyzes nitrite reduction by menaquinol and is made up of NrfA and NrfH, two c-type cytochromes. NrfA is the catalytic subunit; its crystal structure is known. NrfH belongs to the NapC/NirT family of membrane-bound c-type cytochromes and mediates electron transport between menaquinol and NrfA. It is demonstrated here by MALDI MS that four heme groups are attached to NrfH. A Delta nrfH deletion mutant of W. succinogenes was constructed by replacing the nrfH gene with a kanamycin-resistance gene cartridge. This mutant did not form the NrfA protein, probably because of a polar effect of the mutation on nrfA expression. The nrfHAIJ gene cluster was restored by integration of an nrfH-containing plasmid into the genome of the Delta nrfH mutant. The resulting strain had wild-type properties with respect to growth by nitrite respiration and nitrite reductase activity. A mutant (stopH) that contained the nrfHAIJ locus with nrfH modified by two artificial stop codons near its 5' end produced wild-type amounts of NrfA in the absence of the NrfH protein. NrfA was located exclusively in the soluble cell fraction of the stopH mutant, indicating that NrfH acts as the membrane anchor of the NrfHA complex in wild-type bacteria. The stopH mutant did not grow by nitrite respiration and did not catalyze nitrite reduction by formate, indicating that the electron transport is strictly dependent on NrfH. The NrfH protein seems to be an unusual member of the NapC/NirT family as it forms a stable complex with its redox partner protein NrfA.

In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the investigation of fragile single molecular species by gas-phase chromatography. The latest success with the heaviest group 6 transactinide seaborgium is highlighted. The formation of a very volatile hexacarbonyl compound Sg(CO)6 was observed similarly to its lighter homologues molybdenum and tungsten. The interactions of these gaseous carbonyl complex compounds with quartz surfaces were investigated by thermochromatography. Second-generation experiments are under way to investigate the intramolecular bond between the central metal atom of the complexes and the ligands addressing the influence of relativistic effects in the heaviest compounds. Our contribution comprises some aspects of the ongoing challenging experiments as well as an outlook towards other interesting compounds related to volatile complex compounds in the gas phase.

A cation-exchange procedure was developed for separating Nb from Ta, Pa from Ta, and Nb, Pa, and Ta from Zr, Hf, and lanthanides in dilute HC1/HF solutions. The stability of the fluoride complexes of Group IV and V elements decreases in the following order: Nb ∼ Pa > Zr > Hf > Ta. This procedure can be used in experiments on synthesis of superheavy nuclei for isolation of Db from the reaction products and for its chemical identification.

The Z protein is the matrix protein of arenaviruses and has been identified as the main driving force for budding. Both LCMV and Lassa virus Z proteins bud from cells in the absence of other viral proteins as enveloped virus-like particles. Z accumulates near the inner surface of the plasma membrane where budding takes place. Furthermore, biochemical data have shown that Z is strongly membrane associated. The primary sequence of Z lacks a typical transmembrane domain and until now it is not understood by which mechanism Z is able to interact with cellular membranes. In this report, we analyzed the role of N-terminal myristoylation for the membrane binding of Lassa virus Z. We show that disruption of the N-terminal myristoylation signal by substituting the N-terminal glycine with alanine (Z-G2A mutant) resulted in a significant reduction of Z protein association with cellular membranes. Furthermore, removal of the myristoylation site resulted in a relocalization of Z from a punctuate distribution to a more diffuse cellular distribution pattern. Finally, treatment of Lassa virus-infected cells with various myristoylation inhibitors drastically reduced efficient Lassa virus replication. Our data indicate that myristoylation of Z is critical for its binding ability to lipid membranes and thus, for effective virus budding.

Lassa virus glycoprotein is synthesised as a precursor (preGP-C) into the lumen of the endoplasmic reticulum. After cotranslational cleavage of the signal peptide, the immature GP-C is posttranslationally processed into the N-terminal subunit GP-1 and the C-terminal subunit GP-2 by the host cell subtilase SKI-1/S1P. The glycoprotein precursor contains eleven potential N-glycosylation sites. In this report, we investigated the effect of each N-glycan on proteolytic cleavage and cell surface transport by disrupting the consensus sequences of eleven potential N-glycan attachment sites individually. Five glycoprotein mutants with disrupted N-glycosylation sites were still proteolytically processed, whereas the remaining N-glycosylation sites are necessary for GP-C cleavage. Despite the lack of proteolytic processing, all cleavage-defective mutants were transported to the cell surface and remained completely endo H-sensitive. The findings indicate that N-glycans are needed for correct conformation of GP-C in order to be cleaved by SKI-1/S1P.