The heaviest elements to have been chemically characterized are seaborgium (element 106), bohrium (element 107) and hassium (element 108). All three behave according to their respective positions in groups 6, 7 and 8 of the periodic table, which arranges elements according to their outermost electrons and hence their chemical properties. However, the chemical characterization results are not trivial: relativistic effects on the electronic structure of the heaviest elements can strongly influence chemical properties. The next heavy element targeted for chemical characterization is element 112; its closed-shell electronic structure with a filled outer s orbital suggests that it may be particularly susceptible to strong deviations from the chemical property trends expected within group 12. Indeed, first experiments concluded that element 112 does not behave like its lighter homologue mercury. However, the production and identification methods used cast doubt on the validity of this result. Here we report a more reliable chemical characterization of element 112, involving the production of two atoms of (283)112 through the alpha decay of the short-lived (287)114 (which itself forms in the nuclear fusion reaction of 48Ca with 242Pu) and the adsorption of the two atoms on a gold surface. By directly comparing the adsorption characteristics of (283)112 to that of mercury and the noble gas radon, we find that element 112 is very volatile and, unlike radon, reveals a metallic interaction with the gold surface. These adsorption characteristics establish element 112 as a typical element of group 12, and its successful production unambiguously establishes the approach to the island of stability of superheavy elements through 48Ca-induced nuclear fusion reactions with actinides.
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 belongs to the large family of Arenaviridae, including the closely related Lymphocytic choriomeningitis virus (LCMV) and other important human pathogens like Guanarito virus, Junin virus, and Machupo virus. Lassa virus is the etiologic agent of a hemorrhagic fever endemic in West Africa, where annually up to 100,000 cases of clinically apparent Lassa fever occur. Up to 20% of these patients develop hemorrhagic manifestations with a total mortality of 10 to 15% (28,29). In recent years this disease has been increasingly exported from regions where it is endemic to other parts of the world (36).Lassa virus consists of a helical nucleocapsid containing a bisegmented RNA genome surrounded by a lipid bilayer with integrated glycoprotein spikes. Each single-stranded RNA encodes two viral genes in an ambisense coding strategy separated by an intergenic region. The small RNA encodes the nucleoprotein NP (60 kDa) and the immature glycoprotein precursor pre-GP-C (80 kDa), which is cotranslationally cleaved by signal peptidase into GP-C (75 kDa) and a stable signal peptide of 58 amino acids (aa) (10). GP-C is cleaved posttranslationally by subtilase SKI-1/S1P into the N-terminal subunit GP-1 (40 kDa) and the membrane-bound subunit GP-2 (35 kDa). Both subunits are incorporated in virus particles (24,25). The large RNA segment encodes the RNAdependent RNA polymerase L (ϳ200 kDa) and the Z protein with a length of 99 amino acids and a molecular mass of approximately 11 kDa (33,35).During the last few years, the role of the arenavirus Z protein has been elucidated in respect to virus replication. The Z protein of Lassa virus and LCMV contains a RING motif and was shown to have zinc-binding activity (34). Most of the information so far indicates a regulatory role of Z, as the LCMV Z protein was shown to bind to the promyelotic leukemia protein and to relocate nuclear structures formed by the promyelotic leukemia protein (2, 4). The LCMV Z protein has also been reported to interact with the nuclear fraction of the ribosomal protein P0 and with the eukaryotic translation initiation factor eIF4E (3, 7). Furthermore, the Z protein of Tacaribe virus is implicated in RNA synthesis and genome replication in the early stage of infection (13). In contrast, the Z protein of LCMV was not required for RNA replication and transcription in a LCMV minigenome system. Moreover, the Z pro...
Transactinides / Element 114 / Adsorption / ThermochromatographySummary. Recently, the chemical investigation of element 112 revealed a highly volatile, noble metallic behaviour, as expected for the last group 12 member of the periodic table. The observed volatility and chemical inertness were ascribed to the growing influence of relativistic effects on the chemical properties of the heaviest elements with increasing nuclear charge. Here, we report for the first time on gas phase chemical experiments aiming at a determination of element 114 properties. This element was investigated using its isotopes 287 114 and 288 114 produced in the nuclear fusion reactions of 48 Ca with 242 Pu and 244 Pu, respectively. Identification of three atoms of element 114 in thermochromatography experiments and their deposition pattern on a gold surface indicates that this element is at least as volatile as simultaneously investigated elements Hg, At, and element 112. This behaviour is rather unexpected for a typical metal of group 14.
The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes (269)Hs (refs 8, 9) and (270)Hs (ref. 10) in the fusion reaction between (26)Mg and (248)Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO(4), for which we determine an enthalpy of adsorption on our detector surface that is comparable to the adsorption enthalpy determined under identical conditions for the osmium oxide OsO(4). These results provide evidence that the chemical properties of hassium and its lighter homologue osmium are similar, thus confirming that hassium exhibits properties as expected from its position in group 8 of the periodic table.
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