Ultrafine heat-induced structural perturbations of bone mineral at the individual nanocrystal level

International audienc

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

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

Comparison of tendon fiber structures between wild type and TIEG knockout mice using synchrotron microdiffraction

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In situ μ-Raman spectroscopy study of an isolated micrometer-size pseudo-single crystal of β-H2NiO2 under electrochemical operation

The response of micrometric pseudo-single crystals of β-H2NiO2, deposited on an Au substrate and submitted to high rate charge/discharge cycling under controlled current conditions, is studied by in situ μ-Raman spectroscopy. The intensities of the Raman background and of the hydroxyl stretching band are used to probe in time the single-particle surface and bulk oxidation states respectively. Results, obtained in the absence of electrical binders and chemical dopants, substantiate previous electrochemical investigations suggesting that the occurrence of the nickel electrode activation process is related to the formation of a thin surface limiting layer hindering the active material capacity to store and deliver energy. The feasibility of in situ μ-Raman spectroscopy on nickel hydroxide single particles submitted to electrochemical operation is demonstrated for the first time

Structural and electrical properties of silicon nitride films prepared by multipolar plasma‐enhanced deposition

A new system of dielectric deposition using a multipolar plasma enhanced by a hot filament has been used to deposit multipolar plasma chemical vapor deposition silicon nitride films on various substrates (GaAs, Si, GaInAs, etc.). Using in situ kinetic ellipsometry during the depositions, the flow ratio SiH4/N2 has been optimized to form as dense silicon nitride as possible. The density variation has been attributed to a variable amount of oxygen in the films certainly in the form of silicon dioxide. Using Rutherford backscattering and spectroscopic ellipsometry, the amounts of oxygen have been measured precisely. Using infrared absorption, we have demonstrated the low hydrogen concentration of our films compared to plasma-enhanced chemical vapor deposition ones. At constant flow ratio, we have demonstrated the effect of the deposition rate on the stoichiometry of the films. Films deposited at very low deposition rates (24 Å/min). The conduction mechanism appears ionic in oxygen-rich silicon nitride films and controlled by a Poole–Frenkel effect in the case of moderate deposition rates