Photoswitchable diacylglycerols enable optical control of protein kinase C.

Increased levels of the second messenger lipid diacylglycerol (DAG) induce downstream signaling events including the translocation of C1-domain-containing proteins toward the plasma membrane. Here, we introduce three light-sensitive DAGs, termed PhoDAGs, which feature a photoswitchable acyl chain. The PhoDAGs are inactive in the dark and promote the translocation of proteins that feature C1 domains toward the plasma membrane upon a flash of UV-A light. This effect is quickly reversed after the termination of photostimulation or by irradiation with blue light, permitting the generation of oscillation patterns. Both protein kinase C and Munc13 can thus be put under optical control. PhoDAGs control vesicle release in excitable cells, such as mouse pancreatic islets and hippocampal neurons, and modulate synaptic transmission in Caenorhabditis elegans. As such, the PhoDAGs afford an unprecedented degree of spatiotemporal control and are broadly applicable tools to study DAG signaling

Atomistic level studies on the tensile behavior of GaN nanotubes under uniaxial tension

Molecular dynamics method with the Stillinger-Weber (SW) potential has been employed to study the responses of GaN nanotubes (GaNNTs) to a uniaxial tensile load along the axial direction. It has been revealed that GaNNTs exhibits a completely different tensile behavior at different temperatures, i.e. ductility at higher deformation temperatures and brittleness at lower temperatures, leading to a brittle to ductile transition (BDT). Both the BDT temperature and the critical stress increases with increasing thickness of GaNNTs, and the critical stress at higher temperature are lower than those at lower temperature. These results on the tensile behaviors of GaNNTs in an atomic level will provide a good reference to its promising applications. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 200862.25.+g Mechanical properties of nanoscale systems, 65.80.+n Thermal properties of small particles, nanocrystals, and nanotubes, 02.70.Ns Molecular dynamics and particle methods,