Heavy Metal and Rock in Space: Cluster RAPID Observations of Fe and Si

Metallic and silicate ions carry essential information about the evolution of the Earth and near-Earth small bodies. Despite this, there has so far been very little focus on ions with atomic masses higher than oxygen in the terrestrial magnetosphere. In this paper, we report on abundances and properties of energetic ions with masses corresponding to that of silicon (Si) and iron (Fe) in Earth's geospace. The results are based on a newly derived data product from the Research with Adaptive Particle Imaging Detectors on Cluster. We find traces of both Si and Fe in all of the regions covered by the spacecraft, with the highest occurrence rates and highest intensities in the inner magnetosphere. We also find that the Fe and Si abundances are modulated by solar activity. During solar maximum, the probability of observing Fe and Si in geospace increases significantly. On the other hand, we find little or no direct correlation between geomagnetic activity and Si and Fe abundance in the magnetosphere. Both Si and Fe in the Earth's magnetosphere are inferred to be primarily of solar wind origin.publishedVersio

Isolation, crystallization, and investigation of ribosomal protein S8 complexed with specific fragments of rRNA of bacterial or archaeal origin. Biochemistry 66

Study of the nature of protein-rRNA complexes is a topical problem of modern molecular biology. Structural studies of rRNA-protein complexes are the most direct and precise method of analysis of these interactions. Because ribosomal proteins are most conservative during evolution, their complexes with specific RNA fragments provide an interesting model for studying RNA-protein interactions. Ribosomal protein S8 from E. coli plays a key role in assembling the small ribosomal subunit The major region of protein S8 binding on 16S rRNA was determined by partial hydrolysis with restric tion endonucleases The binding sites of protein S8 on 16S rRNA are similar in E. coli and T. thermophilus. It was shown that ACCELERATED PUBLICATION 0006 2979/01/6609 0948$25.00 ©2001 MAIK "Nauka / Interperiodica" * To whom correspondence should be addressed. Vol. 66, No. 9, 2001, pp. 948 953. Translated from Biokhimiya, Vol. 66, No. 9, 2001, pp. 1165 1171. Original Russian Text Copyright © 2001 Abstract-The core ribosomal protein S8 binds to the central domain of 16S rRNA independently of other ribosomal proteins and is required for assembling the 30S subunit. It has been shown with E. coli ribosomes that a short rRNA fragment restrict ed by nucleotides 588 602 and 636 651 is sufficient for strong and specific protein S8 binding. In this work, we studied the complexes formed by ribosomal protein S8 from Thermus thermophilus and Methanococcus jannaschii with short rRNA frag ments isolated from the same organisms. The dissociation constants of the complexes of protein S8 with rRNA fragments were determined. Based on the results of binding experiments, rRNA fragments of different length were designed and syn thesized in preparative amounts in vitro using T7 RNA polymerase. Stable S8-RNA complexes were crystallized. Crystals were obtained both for homologous bacterial and archaeal complexes and for hybrid complexes of archaeal protein with bac terial rRNA. Crystals of the complex of protein S8 from M. jannaschii with the 37 nucleotide rRNA fragment from the same organism suitable for X ray analysis were obtained

Structure of ribosomal protein TL5 complexed with RNA provides new insights into the CTC family of stress proteins

The crystal structure of Thermus thermophilus ribosomal protein TL5 in complex with a fragment of Escherichia coli 5S rRNA has been determined at 2.3 Å resolution. The protein consists of two domains. The structure of the N-terminal domain is close to the structure of E. coli ribosomal protein L25, but the C-terminal domain represents a new fold composed of seven -strands connected by long loops. TL5 binds to the RNA through its N-terminal domain, whereas the C-terminal domain is not included in this interaction. Cd2+ ions, the presence of which improved the crystal quality significantly, bind only to the protein component of the complex and stabilize the protein molecule itself and the interactions between the two molecules in the asymmetric unit of the crystal. The TL5 sequence reveals homology to the so-called general stress protein CTC. The hydrophobic cores which stabilize both TL5 domains are highly conserved in CTC proteins. Thus, all CTC proteins may fold with a topology close to that of TL5

Giotto Spacecraft

International audienceThe Giotto spacecraft (Fig. 1), the first ESA (European Space Agency) interplanetary probe, was designed to flyby comet Halley. Launched on 2 July 1985 by an Ariane-1 rocket from Kourou, Giotto succeeded in approaching the cometary nucleus to within 600 km on 14 March 1986. Through its first accurate images of a nucleus and in situ studies of gases and dust particles within a coma, the mission has revealed the complexity of comets. Afterwards, the Giotto spacecraft was re-oriented in order to study comet Grigg-Skjellerup, which was flown by on 10 July 1992, at a nucleus distance in the 150–200 km range