Comparative analysis of RNA regulatory elements of amino acid metabolism genes in Actinobacteria

BACKGROUND: Formation of alternative structures in mRNA in response to external stimuli, either direct or mediated by proteins or other RNAs, is a major mechanism of regulation of gene expression in bacteria. This mechanism has been studied in detail using experimental and computational approaches in proteobacteria and Firmicutes, but not in other groups of bacteria. RESULTS: Comparative analysis of amino acid biosynthesis operons in Actinobacteria resulted in identification of conserved regions upstream of several operons. Classical attenuators were predicted upstream of trp operons in Corynebacterium spp. and Streptomyces spp., and trpS and leuS genes in some Streptomyces spp. Candidate leader peptides with terminators were observed upstream of ilvB genes in Corynebacterium spp., Mycobacterium spp. and Streptomyces spp. Candidate leader peptides without obvious terminators were found upstream of cys operons in Mycobacterium spp. and several other species. A conserved pseudoknot (named LEU element) was identified upstream of leuA operons in most Actinobacteria. Finally, T-boxes likely involved in the regulation of translation initiation were observed upstream of ileS genes from several Actinobacteria. CONCLUSION: The metabolism of tryptophan, cysteine and leucine in Actinobacteria seems to be regulated on the RNA level. In some cases the mechanism is classical attenuation, but in many cases some components of attenuators are missing. The most interesting case seems to be the leuA operon preceded by the LEU element that may fold into a conserved pseudoknot or an alternative structure. A LEU element has been observed in a transposase gene from Bifidobacterium longum, but it is not conserved in genes encoding closely related transposases despite a very high level of protein similarity. One possibility is that the regulatory region of the leuA has been co-opted from some element involved in transposition. Analysis of phylogenetic patterns allowed for identification of ML1624 of M. leprae and its orthologs as the candidate regulatory proteins that may bind to the LEU element. T-boxes upstream of the ileS genes are unusual, as their regulatory mechanism seems to be inhibition of translation initiation via a hairpin sequestering the Shine-Dalgarno box

Thermocatalytic conversion of plastics into liquid fuels over clays

Recycling polymer waste is a great challenge in the context of the growing use of plastics. In this review, the comprehensive information on the thermocatalytic conversion of plastics over clays obtained during the last two decades was summarize

Early onset of ground-state deformation in the neutron-deficient polonium isotopes

In-source resonant ionization laser spectroscopy of the even-$A$ polonium isotopes $^{192-210,216,218}$Po has been performed using the $6p^37s$ $^5S_2$ to $6p^37p$ $^5P_2$ ($\lambda=843.38$ nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in $^{200-210}$Po with a previous data set allows to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by Beyond Mean Field calculations.Comment: As submitted to PR

Magnetic moments of 68^{68}Cug,m^{g,m} and 70^{70}Cug,m1,m2^{g,m_{1},m_{2}} nuclei measured by in-source laser spectroscopy

We have obtained information on the atomic hyperfine splitting and, hence, on magnetic moments in neutron rich $^{68, 70}$Cu isotopes by scanning the frequency of the narrow-band laser of the first excitation step in the resonance ionization laser ion source. The deduced magnetic moments are $\mu( ^{68}$Cu$^{g}$, I$^{\pi}$ = 1$^+$) = +2.48(2)(7)$\mu_{N}$ ; $\mu(^{68}$Cu$^{m}$, I$^{\pi}$=6$^{-}$) = +1.24(4)(6)$\mu_{N}$ and $\mu(^{70}$Cu$^{m_{2}}$, I$^{\pi}$=1$^{+}$) = +1.86(4)(6)$\mu_{N}$ ; $\mu(^{70}$Cu$^{g}$, I$^{\pi}$=6$^{-}$) = +1.50(7)(8)$\mu_{N}$. The results of the scans analysis point out on existence of a new isomer in $^{70}$Cu$^{m_{1}}$. It's deduced magnetic moment is (-)3.50(7)(11)$\mu_{N}$ that is in a good agreement with I$^{\pi}$=3$^{-}$ assignment. The method of in-source atomic spectroscopy, as well as the analysis of the obtained data, is described. The results are discussed in terms of single-particle configurations coupled to the $^{68}$Ni core

Coulomb excitation of 73Ga

The B(E2; Ii -> If) values for transitions in 71Ga and 73Ga were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of 71,73Ga at the REX-ISOLDE on-line isotope mass separator facility. The emitted gamma rays were detected by the MINIBALL-detector array and B(E2; Ii->If) values were obtained from the yields normalized to the known strength of the 2+ -> 0+ transition in the 120Sn target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity towards lower excitation energy when adding neutrons beyond N = 40. This supports conclusions from previous studies of the gallium isotopes which indicated a structural change in this isotopical chain between N = 40 and N = 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2- spin and parity for the ground state, the extracted results revealed evidence for a 1/2-; 3/2- doublet near the ground state in 73 31Ga42 differing by at most 0.8 keV in energy