On the validity of the cranking model for 2+-vibrations

The relation of the cranking model to more fundamental methods of determining the generator of a collective state is investigated for the quadrupole case. We are able to show that the heuristic procedure starting with an adiabatic change in the nuclear deformation and splitting the cranking operator according to main quantum number selection rules approximates the true collective states very well. However, for the low-lying collective state the analytic form of the cranking term is completely different from any type of scaling ansatz.     

Li4C60: a polymeric fulleride with a two-dimensional architecture and mixed interfullerene bonding motifs

All known fullerene polymers have interfullerene connections via either [2 + 2] cycloaddition or single C-C bonds. The high-resolution synchrotron X-ray powder diffraction technique was employed here to determine the crystal structure of the Li4C60 fulleride. We find that the ground state of Li4C60 is a two-dimensional polymer with monoclinic crystal symmetry and an unprecedented architecture, combining both the [2 + 2] cycloaddition and the single C-C bridging motifs. The small size of the Li+ cations is crucial in stabilizing the resulting tightly packed polymeric structure.     

Sigmatropic Rearrangement of Vinyl Aziridines: Expedient Synthesis of Cyclic Sulfoximines from Chiral Sulfinimines

A novel rearrangement of 2‐vinyl aziridine 2‐carboxylates to unusual chiral cyclic sulfoximines is described herein. The method allows the synthesis of substituted cyclic sulfoximines in high yields with complete stereocontrol, and tolerates a wide substrate scope. A one‐pot process starting directly from sulfinimines provides access to complex chiral sulfoximines in only two steps from commercially available aldehydes. A mechanistic hypothesis and synthetic application in the formal synthesis of trachelanthamidine, by transformation of a cyclic sulfoximine into a pyrroline, is also disclosed.     

Entrapment of ionic tris(2,2'-bipyridyl) ruthenium(II) in hydrophobic siliceous zeolite: O2 sensing in biological environments

Synthesis of the ionic dye, tris(2,2'-bipyridyl) ruthenium(II) chloride (Ru(bpy) 3 2+.2Cl (-)) within the supercages of a highly hydrophobic zeolite Y is reported. Use of the neutral precursor Ru(bpy)Cl 2(CO) 2 allowed for high loading levels of Ru(bpy) 3 2+ (1 per 7 and 25 supercages). The emission quenching of the Ru(bpy) 3 2+-zeolite crystals dispersed in polydimethoxysiloxane (PDMS) films by dissolved oxygen in water was examined. The quenching data as a function of oxygen concentration was fit to a linear Stern-Volmer plot ( R2 = 0.98). Using the Stern-Volmer plot as calibration, changes in concentration of dissolved oxygen due to reaction with glucose in the presence of glucose oxidase was monitored. Human monocyte-derived macrophages internalized the submicron-sized Ru(bpy) 3 2+-zeolite crystals, and intracellular oxygen concentrations initiated by zymosan-mediated oxidative burst could be monitored by measuring the emission from Ru(bpy) 3 2+ by confocal fluorescence microscopy.     

Separation of Bioactive Prostaglandins and their Metabolites by Reversed-Phase Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Prostaglandins are biological lipid mediators that control a variety of physiological and pathophysiological processes. They...     

Swapping Interface Contacts in the Homodimeric tRNA‐Guanine Transglycosylase: An Option for Functional Regulation

The enzyme tRNA‐guanine transglycosylase, a target to fight Shigellosis, recognizes tRNA only as a homodimer and performs full nucleobase exchange at the wobble position. Active‐site inhibitors block the enzyme function by competitively replacing tRNA. In solution, the wild‐type homodimer dissociates only marginally, whereas mutated variants show substantial monomerization in solution. Surprisingly, one inhibitor transforms the protein into a twisted state, whereby one monomer unit rotates by approximately 130°. In this altered geometry, the enzyme is no longer capable of binding and processing tRNA. Three sugar‐type inhibitors have been designed and synthesized, which bind to the protein in either the functionally competent or twisted inactive state. They crystallize with the enzyme side‐by‐side under identical conditions from the same crystallization well. Possibly, the twisted inactive form corresponds to a resting state of the enzyme, important for its functional regulation.