Nucleic Acids Res

Micro (mi)RNAs are small non-coding RNAs with key regulatory functions. Recent advances in the field allowed researchers to identify their targets. However, much less is known regarding the regulation of miRNAs themselves. The accumulation of these tiny regulators can be modulated at various levels during their biogenesis from the transcription of the primary transcript (pri-miRNA) to the stability of the mature miRNA. Here, we studied the importance of the pri-miRNA secondary structure for the regulation of mature miRNA accumulation. To this end, we used the Kaposi's sarcoma herpesvirus, which encodes a cluster of 12 pre-miRNAs. Using small RNA profiling and quantitative northern blot analysis, we measured the absolute amount of each mature miRNAs in different cellular context. We found that the difference in expression between the least and most expressed viral miRNAs could be as high as 60-fold. Using high-throughput selective 2'-hydroxyl acylation analyzed by primer extension, we then determined the secondary structure of the long primary transcript. We found that highly expressed miRNAs derived from optimally structured regions within the pri-miRNA. Finally, we confirmed the importance of the local structure by swapping stem-loops or by targeted mutagenesis of selected miRNAs, which resulted in a perturbed accumulation of the mature miRNA

Labeling of Multiple HIV-1 Proteins with the Biarsenical-Tetracysteine System

Due to its small size and versatility, the biarsenical-tetracysteine system is an attractive way to label viral proteins for live cell imaging. This study describes the genetic labeling of the human immunodeficiency virus type 1 (HIV-1) structural proteins (matrix, capsid and nucleocapsid), enzymes (protease, reverse transcriptase, RNAse H and integrase) and envelope glycoprotein 120 with a tetracysteine tag in the context of a full-length virus. We measure the impact of these modifications on the natural virus infection and, most importantly, present the first infectious HIV-1 construct containing a fluorescently-labeled nucleocapsid protein. Furthermore, due to the high background levels normally associated with the labeling of tetracysteine-tagged proteins we have also optimized a metabolic labeling system that produces infectious virus containing the natural envelope glycoproteins and specifically labeled tetracysteine-tagged proteins that can easily be detected after virus infection of T-lymphocytes. This approach can be adapted to other viral systems for the visualization of the interplay between virus and host cell during infection

Propriétés magnétiques du grenat d'aluminium et de dysprosium. I. Théorie a 0 °K

It is shown that the application of a strong enough magnetic field on dysprosium aluminium garnet will uncouple those sublattices, the easy magnetization axis of which is normal to the field, from the other sublattices. Thus, this garnet bears much resemblance to Fisher's "superexchange" antiferromagnet. One determines within a molecular field treatment involving twenty four sublattices : 1) the magnetic phase diagram at 0 °K ; 2) the nature of the new phases which a magnetic field is liable to induce ; 3) the ordering températures of theses phases when the magnetic field is applied in the principal directions. Group theory is extensively used to solve these problems. The existence of two nonequivalent easy axes gives this garnet very unusual magnetic properties.On montre que dans le grenat d'aluminium et de dysprosium l'application d'un champ magnétique assez intense est susceptible de découpler les sous-réseaux ayant leur axe de facile aimantation normal au champ des autres sous-réseaux, ce qui confère à ce grenat une grande ressemblance avec l'antiferromagnétique « décoré » de Fisher. Dans un modèle de champ moléculaire à vingt-quatre sous-réseaux, on détermine : 1° le diagramme de phase magnétique à 0 °K ; 2° la nature des phases nouvelles que le champ magnétique peut faire apparaître ; 3° les températures d'ordre de ces phases pour des champs appliqués dans les directions principales. La théorie des groupes est utilisée de manière extensive pour résoudre ces problèmes. L'existence de deux directions de facile aimantation non équivalentes confère à ce grenat des propriétés magnétiques très remarquables

Métamagnétisme d'un antiferromagnétique fortement anisotrope

It is shown that the range of magnetic interactions deeply influences the metamagnetism of the Ising antiferromagnet. In the case of dysprosium aluminium garnet, the values of the threshold fields at which a bulk magnetization of the sample appears are derived semi-empirically for both directions of the applied magnetic field in which the phenomenon has been studied. The thermal behaviour is briefly discussed.On montre l'influence de la portée des interactions magnétiques sur le métamagnétisme d'un antiferromagnétique d'Ising. Par une méthode semi-empirique, on calcule dans le cas du grenat d'aluminium et de dysprosium les valeurs des champs seuils à 0 °K où une aimantation globale du spécimen apparaît pour les deux directions du champ magnétique appliqué dans lesquelles le phénomène a été étudié. On donne une brève interprétation du comportement en fonction de la température

Propriétés magnétiques du grenat d'aluminium et de dysprosium II. Résultats expérimentaux à très basse température

The magnetization of a spherical single crystal of dysprosium aluminium garnet has been measured at T ≃ 0.37 °K as a function of either the strength or the direction of the applied magnetic field. expérimental results are found to agree extremely well with the prédictions of the theory (I), provided this is suitably modified to account for the demagnetizing field. In particular, it has been checked that a strong enough magnetic field applied in the [0, 0, 1] direction does induce antiferromagnetic ordering in those sublattices which are uncoupled from the field ; in the [1, 1, 0] direction, this ordering is found to be ferromagnetic. The parameters q are fitted to the experimental results.On a étudié, à température fixe T ≃ 0,37 °K, l'aimantation d'un cristal sphérique de grenat d'aluminium et de dysprosium en fonction soit de l'intensité, soit de l'orientation du champ appliqué. Les résultats expérimentaux sont en excellent accord avec les prédictions de la théorie (I) assortie de modifications adéquates nécessitées par la présence d'un champ démagnétisant. On a vérifié en particulier qu'un champ fort appliqué dans la direction [0, 0, 1] induisait dans les sous-réseaux découplés du champ un nouvel ordre antiferromagnétique ; dans la direction [1, 1, 0], cet ordre est ferromagnétique. On adapte les paramètres q aux résultats expérimentaux

Soft laser sputtering of GaAs semiconductor surfaces

No abstract availabl

About optimal architecture of plant fibre textile composite for mechanical and sorption properties

International audienceThe aim of this work is to establish simple rules to optimise the architecture of plant woven fabric reinforcement for structural composite applications (sorption and mechanic aspects). For that, the influence of architectural parameters of reinforcement such as the frame, the yarn diameter, the pick count, and the filling rate, was studied from six different flax fabrics (2 quasi-unidirectionals and 4 balanced twills) and two processing techniques (autoclave and hot platen press). On the one hand, in order to normalise the effects of fibre fraction, porosity fraction and architectural parameters, a model was developped to analyse the mechanical properties at the level of the yarn. On the other hand, after demonstrating that the classical model of Fick does not properly fit the sorption of plant fibre textile composite, a two-phase Fick’s diffusion model was applied. It results that the best fabric architecture concerning mechanical and sorption properties is a compromise mixing high filling rate of woven fabrics, small shrinkage of yarns, and small yarn diameter