Oxidation of gallium arsenide in a plasma multipole device. Study of the MOS structures obtained

The oxygen plasma oxidation of GaAs was studied in order to obtain extremely high frequency responses with MOS devices. In the multipole system a homogeneous oxygen plasma of high density can easily be obtained in a large volume. This system is thus convenient for the study of plasma oxidation of GaAs. The electrical properties of the MOS diodes obtained in this way are controlled by interface states, located mostly in the upper half of the band gap where densities in the 10 to the 13th power/(sq cm) (eV) range can be estimated. Despite these interface states the possibility of fabricating MOSFET transistors working mostly in the depletion mode for a higher frequency cut-off still exists

A MANBA mutation resulting in residual beta-mannosidase activity associated with severe leukoencephalopathy: a possible pseudodeficiency variant

<p>Abstract</p> <p>Background</p> <p>β-Mannosidosis (OMIM 248510) is a rare inborn lysosomal storage disorder caused by the deficient activity of β-mannosidase, an enzyme encoded by a single gene (<it>MANBA</it>) located on chromosome 4q22-25. To date, only 20 cases of this autosomal recessive disorder have been described and 14 different <it>MANBA </it>mutations were incriminated in the disease. These are all null mutations or missense mutations that abolish β-mannosidase activity. In this study, we characterized the molecular defect of a new case of β-mannosidosis, presenting with a severe neurological disorder.</p> <p>Methods</p> <p>Genomic DNA was isolated from peripheral blood leukocytes of the patient to allow <it>MANBA </it>sequencing. The identified mutation was engineered by site-directed mutagenesis and the mutant protein was expressed through transient transfection in HEK293T cells. The β-mannosidase expression and activity were respectively assessed by Western blot and fluorometric assay in both leukocytes and HEK293T cells.</p> <p>Results</p> <p>A missense disease-associated mutation, c.1922G>A (p.Arg641His), was identified for which the patient was homozygous. In contrast to previously described missense mutations, this substitution does not totally abrogate the enzyme activity but led to a residual activity of about 7% in the patient's leukocytes, 11% in lymphoblasts and 14% in plasma. Expression studies in transfected cells also resulted in 7% residual activity.</p> <p>Conclusion</p> <p>Correlations between MANBA mutations, residual activity of β-mannosidase and the severity of the ensuing neurological disorder are discussed. Whether the c.1922G>A mutation is responsible for a yet undescribed pseudodeficiency of β-mannosidase is also discussed.</p

Non-coding RNA annotation of the genome of Trichoplax adhaerens

A detailed annotation of non-protein coding RNAs is typically missing in initial releases of newly sequenced genomes. Here we report on a comprehensive ncRNA annotation of the genome of Trichoplax adhaerens, the presumably most basal metazoan whose genome has been published to-date. Since blast identified only a small fraction of the best-conserved ncRNAs—in particular rRNAs, tRNAs and some snRNAs—we developed a semi-global dynamic programming tool, GotohScan, to increase the sensitivity of the homology search. It successfully identified the full complement of major and minor spliceosomal snRNAs, the genes for RNase P and MRP RNAs, the SRP RNA, as well as several small nucleolar RNAs. We did not find any microRNA candidates homologous to known eumetazoan sequences. Interestingly, most ncRNAs, including the pol-III transcripts, appear as single-copy genes or with very small copy numbers in the Trichoplax genome

UtpA and UtpB chaperone nascent pre-ribosomal RNA and U3 snoRNA to initiate eukaryotic ribosome assembly

Early eukaryotic ribosome biogenesis involves large multi-protein complexes, which co-transcriptionally associate with pre-ribosomal RNA to form the small subunit processome. The precise mechanisms by which two of the largest multi-protein complexes—UtpA and UtpB—interact with nascent pre-ribosomal RNA are poorly understood. Here, we combined biochemical and structural biology approaches with ensembles of RNA–protein cross-linking data to elucidate the essential functions of both complexes. We show that UtpA contains a large composite RNA-binding site and captures the 5′ end of pre-ribosomal RNA. UtpB forms an extended structure that binds early pre-ribosomal intermediates in close proximity to architectural sites such as an RNA duplex formed by the 5′ ETS and U3 snoRNA as well as the 3′ boundary of the 18S rRNA. Both complexes therefore act as vital RNA chaperones to initiate eukaryotic ribosome assembly

Combination of Nanoindentation and Quantitative Backscattered Electron Imaging Revealed Altered Bone Material Properties Associated with Femoral Neck Fragility

Osteoporotic fragility fractures were hypothesized to be related to changes in bone material properties and not solely to reduction in bone mass. We studied cortical bone from the superior and inferior sectors of whole femoral neck sections from five female osteoporotic hip fracture cases (74–92 years) and five nonfractured controls (75–88 years). The typical calcium content (CaPeak) and the mineral particle thickness parameter (T) were mapped in large areas of the superior and inferior regions using quantitative backscattered electron imaging (qBEI) and scanning small-angle X-ray scattering, respectively. Additionally, indentation modulus (E) and hardness (H) (determined by nanoindentation) were compared at the local level to the mineral content (CaInd) at the indent positions (obtained from qBEI). CaPeak (−2.2%, P = 0.002), CaInd (−1.8%, P = 0.048), E (−5.6%, P = 0.040), and H (−6.0%, P = 0.016) were significantly lower for the superior compared to the inferior region. Interestingly, CaPeak as well as CaInd were also lower (−2.6%, P = 0.006, and –3.7%, P = 0.002, respectively) in fracture cases compared to controls, while E and H did not show any significant reduction. T values were in the normal range, independent of region (P = 0.181) or fracture status (P = 0.551). In conclusion, it appears that the observed femoral neck fragility is associated with a reduced mineral content, which was not accompanied by a reduction in stiffness and hardness of the bone material. This pilot study suggests that a stiffening process in the organic matrix component contributes to bone fragility independently of mineral content

Hardness testing under a different light: combining synchrotron X-ray microdiffraction and indentation techniques for polymer fibres studies

International audienceDeformation mechanisms occurring on the nanometer scale during indentation of bulk polymer fibres were investigated by means of scanning wide-angle diffraction scattering (WAXS) using beams of micrometer size at the ESRF microfocus beamline (ID13). Elastic processes could be evidenced in-situ using a dedicated microindenter device. The most important changes appear in the form of local crystalline reorientation which can be quantified by analysis of the azimuthal profiles of the WAXS reflections. The texture and phase-transitions induced by plastic deformation at higher loads was also measured and the differences between high performance fibres and a more traditional semicrystalline polymer are emphasized

Towards a better understanding of alteration phenomena of archaeological bone by a closer look at the organic mineral association at micro and nanoscale. Preliminary results on neolithic samples from Chalain lake site 19, Jura, France

International audienceIn this paper we present the extension of existing analytical schemes for the precise evaluation of archaeological bone preservation states. The new methodological developments concerning the study of the morphological and structural features of archaeological bones at micro- and nanoscale are emphasized in order to elucidate fine diagenetic modifications and to better understand the underlying alteration mechanisms. A combination of synchrotron X-ray microtomography, infrared micro-spectroscopy imaging and quantitative scanning small-angle X-ray scattering (sSAXS) imaging allowed studying micromorphological changes and the distribution of the organic and mineral components of bone at a histological level. Transmission electron microscopy gives precise information on changes of apatite crystal dimensions, orientations, periodicity of collagen fiber arrangement and crystal distributions within the fibers in archaeological bone. It allows establishing criteria to evaluate more precisely the preservation state of archaeological bone material with respect to modern references. The potential of these methods is highlighted on the basis of the study of some macroscopically well preserved archaeological bone samples from the Chalain lake station 19, Neolithic period, Jura, France. The investigations allowed a differentiation in preservation state between these samples and the postulation of an alteration sequence in such humid chalk-rich burial environments.Dans cet article nous présentons une extension de méthodes analytiques existantes pour évaluer précisément l’état de conversation des os archéologiques. Les nouveaux développements méthodologiques concernent particulièrement l’étude des caractéristiques structurales et morphologiques des ossements archéologiques aux échelles micro- et nanoscopiques afin de pouvoir élucider des modifications diagénetiques fines et de mieux comprendre les mécanismes d’altération sous-jacents. Une combinaison de microtomographie X, de micro-spectroscopie infrarouge et de micro-imagerie SAXS à balayage au synchrotron a permis d’étudier les altérations micromorphologiques et la répartition spatiale des composés organiques et minéraux dans les os à l’échelle histologiques. La microscopie électronique à transmission donne des informations précises sur les modifications de la taille des cristaux, leur orientation, la périodicité des arrangements des fibres collagéniques ainsi que la répartition des cristaux au sein des fibres dans l’os archéologique. Ces observations ont permis d’établir des paramétres permettant l’évaluation fine des modifications diagénetiques de la structure des os archéologiques en comparaison aux références modernes. Le potentiel de ces méthodes est illustré grâce à l’étude d’os archéologiques qui sont bien préservés à l’échelle macroscopique provenant du site néolithique de Chalain 19, Jura, France. Cette investigation a permis de montrer des différences dans l’état de conservation de ces os et permet de proposer une séquence d’altération pour les os enfouis dans des environnements humides et riches en craie

The three dimensional arrangement of the mineralized collagen fibers in elephant ivory and its relation to mechanical and optical properties

International audienceElephant tusks are composed of dentin or ivory, a hierarchical and composite biological material made of mineralized collagen fibers (MCF). The specific arrangement of the MCF is believed to be responsible for the optical and mechanical properties of the tusks. Especially the MCF organization likely contributes to the formation of the bright and dark checkerboard pattern observed on polished sections of tusks (Schreger pattern). Yet, the precise structural origin of this optical motif is still controversial. We hereby address this issue using complementary analytical methods (small and wide angle X-ray scattering, cross-polarized light microscopy and scanning electron microscopy) on elephant ivory samples and show that MCF orientation in ivory varies from the outer to the inner part of the tusk. An external cohesive layer of MCF with fiber direction perpendicular to the tusk axis wraps the mid-dentin region, where the MCF are oriented mainly along the tusk axis and arranged in a plywood-like structure with fiber orientations oscillating in a narrow angular range. This particular oscillating-plywood structure of the MCF and the birefringent properties of the collagen fibers, likely contribute to the emergence of the Schreger pattern, one of the most intriguing macroscopic optical patterns observed in mineralized tissues and of great importance for authentication issues in archeology and forensic sciences