Clathrin light chains' role in selective endocytosis influences antibody isotype switching

Clathrin, a cytosolic protein composed of heavy and light chain subunits, assembles into a vesicle coat, controlling receptor-mediated endocytosis. To establish clathrin light chain (CLC) function in vivo, we engineered mice lacking CLCa, the major CLC isoform in B lymphocytes, generating animals with CLC-deficient B cells. In CLCa-null mice, the germinal centers have fewer B cells, and they are enriched for IgA-producing cells. This enhanced switch to IgA production in the absence of CLCa was attributable to increased transforming growth factor β receptor 2 (TGFβR2) signaling resulting from defective endocytosis. Internalization of C-X-C chemokine receptor 4 (CXCR4), but not CXCR5, was affected in CLCa-null B cells, and CLC depletion from cell lines affected endocytosis of the δ-opioid receptor, but not the β2-adrenergic receptor, defining a role for CLCs in the uptake of a subset of signaling receptors. This instance of clathrin subunit deletion in vertebrates demonstrates that CLCs contribute to clathrin’s role in vivo by influencing cargo selectivity, a function previously assigned exclusively to adaptor molecules

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Ion Acceleration - Target Normal Sheath Acceleration

Energetic ions have been observed since the very first laser-plasma experiments.Their origin was found to be the charge separation of electrons heated by thelaser, which transfers energy to the ions accelerated in the field. The adventof ultra-intense lasers with pulse lengths in the femtosecond regime resulted inthe discovery of very energetic ions with characteristics quite different fromthose driven by long-pulse lasers. Discovered in the late 1990s, these ion beamshave become the focus of intense research worldwide, because of their uniqueproperties and high particle numbers. Based on their non-isotropic, beam-likebehaviour, which is always perpendicular to the emitting surface, theacceleration mechanism is called target normal sheath acceleration (TNSA). Weaddress the physics of the mechanism and its dependence on laser and targetparameters. Techniques to explore and diagnose the beams, to make them usefulfor applications, are also addressed

Parametric Amplification Of Laser-Driven Acceleration In A Plasma Channel

Two-dimensional particle-in-cell simulations are presented for a laser-irradiated solid-density target with and without an underdense preplasma. It is shown that an underdense preplasma can generate an energetic electron tail in addition to the warm electrons generated at the critical surface. Preplasma electrons are accelerated in a quasi-static positively charged channel formed by the laser. At ultra-relativistic laser intensities (a(0) = 10), the acceleration mechanism is not sensitive to the laser polarization. An energetic tail with energies significantly exceeding the energy expected for a single electron in a vacuum is present in simulations with s and p-polarized beams. This suggests that the mechanism of parametric amplification of laser-driven electron acceleration is a likely explanation for the observed phenomenon.Institute for Fusion Studie