Collège de France

About: Collège de France is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Dopamine. The organization has 6541 authors who have published 11983 publications receiving 648742 citations. The organization is also known as: College de France.

A directional strategy for monitoring Cre-mediated recombination at the cellular level in the mouse

Abstract: Functional redundancies, compensatory mechanisms, and lethal phenotypes often prevent the full analysis of gene functions through generation of germline null mutations in the mouse The use of site-specific recombinases, such as Cre, which catalyzes recombination between loxP sites, has allowed the engineering of mice harboring targeted somatic mutations, which are both temporally controlled and cell-type restricted Many Cre-expressing mouse lines exist, but only a few transgenic lines are available that harbor a reporter gene whose expression is dependent on a Cre-mediated event Moreover, their use to monitor gene ablation at the level of individual cells is often limited, as in some tissues the reporter gene may be silenced, be affected by position-effect variegation, or reside in a chromatin configuration inaccessible for recombination Thus, one cannot validly extrapolate from the expression of a reporter transgene to an identical ablation pattern for the conditional allele of a given gene By combining the ability of Cre recombinase to invert or excise a DNA fragment, depending on the orientation of the flanking loxP sites, and the availability of both wild-type (WT) and mutant loxP sites, we designed a Cre-dependent genetic switch (FLEx switch) through which the expression of a given gene is turned off, while the expression of another one is concomitantly turned on We demonstrate the efficiency and reliability of this switch to readily detect, in the mouse, at the single cell level, Cre-mediated gene ablation We discuss how this strategy can be used to generate genetic modifications in a conditional manner

Activation of surface oxygen sites on an iridium-based model catalyst for the oxygen evolution reaction

Abstract: The oxygen evolution reaction (OER) is of prime importance in multiple energy storage devices; however, deeper mechanistic understanding is required to design enhanced electrocatalysts for the reaction. Current understanding of the OER mechanism based on oxygen adsorption on a metallic surface site fails to fully explain the activity of iridium and ruthenium oxide surfaces, and the drastic surface reconstruction observed for the most active OER catalysts. Here we demonstrate, using La2LiIrO6 as a model catalyst, that the exceptionally high activity found for Ir-based catalysts arises from the formation of active surface oxygen atoms that act as electrophilic centres for water to react. Moreover, with the help of transmission electron microscopy, we observe drastic surface reconstruction and iridium migration from the bulk to the surface. Therefore, we establish a correlation between surface activity and surface stability for OER catalysts that is rooted in the formation of surface reactive oxygen.

Fingering instability of thin spreading films driven by temperature gradients

Abstract: THE dynamics of spreading of thin liquid films are important to many technological and biological processes, including tertiary oil recovery, coating processes, the formation and protection of microchips and biological cell interactions. The spontaneous spreading of thin liquid films under capillary forces alone is typically a slow process. An applied force—gravitational or centrifugal, or a surface shear stress—can be used to drive the spreading more quickly1,2. Recent experimental3,4 and theoretical5 studies have revealed that in all of these cases of forced spreading, the liquid front undergoes a fingering instability. Here we report another example of such unstable driven flow, this time caused by the Marangoni effect6, in which a temperature gradient induces a gradient of surface tension which drives the spreading process.

Bouncing transitions on microtextured materials

Abstract: A drop of water thrown on a super-hydrophobic solid will often bounce off. Here we discuss the conditions to be fulfilled on the surface design (which provides super-hydrophobicity) to observe such a behavior. This allows us to precise how a material can be made water-repellent. We show in particular how the reduction of the scale of the microstructure provides a robust water repellency, and describe some peculiarities of violent shocks on such surfaces.