Synthesis and characterization of nanocrystalline U1−x_{1-x}Pux_{x}O2(+y)_{2(+y)} mixed oxides

We report here the first synthesis of mixed oxide U$_{1-x}$Pu$_{x}$O$_{2(+y)}$ nanoparticles. The obtained nanopowders were characterized by X-ray diffraction, thermal ionization mass spectrometry, transmission electron microscopy, Raman spectroscopy, and U M$_{4}$ edge high-energy-resolution X-ray absorption near edge structure (HR-XANES). The HR-XANES spectra give evidence for the partial oxidation of U$^{IV}$ to U$^{V}$. This novel route toward the formation of actinide–actinide solid solution opens research opportunities that are not accessible using bulk materials. We give details on the X-ray diffraction study on plutonium oxalate hexahydrate, as a reagent for the synthesis of such nanoparticles

Structures of active melanocortin-4 receptor−Gs-protein complexes with NDP-α-MSH and setmelanotide

The melanocortin-4 receptor (MC4R), a hypothalamic master regulator of energy homeostasis and appetite, is a class A G-protein-coupled receptor and a prime target for the pharmacological treatment of obesity. Here, we present cryo-electron microscopy structures of MC4R–Gs-protein complexes with two drugs recently approved by the FDA, the peptide agonists NDP-α-MSH and setmelanotide, with 2.9 Å and 2.6 Å resolution. Together with signaling data from structure-derived MC4R mutants, the complex structures reveal the agonist-induced origin of transmembrane helix (TM) 6-regulated receptor activation. The ligand-binding modes of NDP-α-MSH, a high-affinity linear variant of the endogenous agonist α-MSH, and setmelanotide, a cyclic anti-obesity drug with biased signaling toward Gq/11, underline the key role of TM3 in ligand-specific interactions and of calcium ion as a ligand-adaptable cofactor. The agonist-specific TM3 interplay subsequently impacts receptor–Gs-protein interfaces at intracellular loop 2, which also regulates the G-protein coupling profile of this promiscuous receptor. Finally, our structures reveal mechanistic details of MC4R activation/inhibition, and provide important insights into the regulation of the receptor signaling profile which will facilitate the development of tailored anti-obesity drugs

Pore formation upon nitriding iron and iron-based alloys: the role of alloying elements and grain boundaries

August 2, 1931. Kjerulfs [Kjerulf] Fjord. Through to Dickson [Dicksons] Fjord. In background: mts. [mountains] forming eastern side of Unknown Valley, here seen just south of L.A.B.'s Scoop Mt. [Mountain]. Photo 24-F-4. Below mts. [mountains] Hisinger Glacier [Hisinger Gletscher] is seen in Unknown Valley, coming from the S.W. and descending N.E. In extreme right of background, above horizon to the south, is seen a peak or nanatak rising above the glacier. Photos 24-F-5 and 26-H-18. In foreground are streams rising in Hisinger Glacier [Hisinger Gletscher] and flowing into pond-like lake (shown here at its greatest width) and from this the stream of Left valley (right of photo) has its source and flows down through Left Valley and continues through Main Valley out into the inner end of Kjerulfs [Kjerulf] Fjord. Photo taken from southern end of Left Valley, looking S.S.E