Site-directed coordination chemistry with P22 virus-like particles

Protein cage nanoparticles (PCNs) are attractive platforms for developing functional nanomaterials using biomimetic approaches for functionalization and cargo encapsulation. Many strategies have been employed to direct the loading of molecular cargos inside a wide range of PCN architectures. Here we demonstrate the exploitation of a metal-ligand coordination bond with respect to the direct packing of guest molecules on the interior interface of a virus-like PCN derived from Salmonella typhimurium bacteriophage P22. The incorporation of these guest species was assessed using mass spectrometry, multiangle laser light scattering, and analytical ultracentrifugation. In addition to small-molecule encapsulation, this approach was also effective for the directed synthesis of a large macromolecular coordination polymer packed inside of the P22 capsid and initiated on the interior surface. A wide range of metals and ligands with different thermodynamic affinities and kinetic stabilities are potentially available for this approach, highlighting the potential for metal-ligand coordination chemistry to direct the site-specific incorporation of cargo molecules for a variety of applications.     

Cyclotron Resonance in the Hidden-Order Phase of URu_{2}Si_{2}

We report the first observation of cyclotron resonance in the hidden-order phase of ultraclean URu_{2}Si_{2} crystals, which allows the full determination of angle-dependent electron-mass structure of the main Fermi-surface sheets. We find an anomalous splitting of the sharpest resonance line under in-plane magnetic-field rotation. This is most naturally explained by the domain formation, which breaks the fourfold rotational symmetry of the underlying tetragonal lattice. The results reveal the emergence of an in-plane mass anisotropy with hot spots along the [110] direction, which can account for the anisotropic in-plane magnetic susceptibility reported recently. This is consistent with the "nematic" Fermi liquid state, in which itinerant electrons have unidirectional correlations.     

Relationship between diffusivity of water molecules inside hydrating tablets and their drug release behavior elucidated by magnetic resonance imaging

We reported previously that sustained release matrix tablets showed zero-order drug release without being affected by pH change. To understand drug release mechanisms more fully, we monitored the swelling and erosion of hydrating tablets using magnetic resonance imaging (MRI). Three different types of tablets comprised of polyion complex-forming materials and a hydroxypropyl methylcellulose (HPMC) were used. Proton density- and diffusion-weighted images of the hydrating tablets were acquired at intervals. Furthermore, apparent self-diffusion coefficient maps were generated from diffusion-weighted imaging to evaluate the state of hydrating tablets. Our findings indicated that water penetration into polyion complex tablets was faster than that into HPMC matrix tablets. In polyion complex tablets, water molecules were dispersed homogeneously and their diffusivity was relatively high, whereas in HPMC matrix tablets, water molecule movement was tightly restricted within the gel. An optimal tablet formulation determined in a previous study had water molecule penetration and diffusivity properties that appeared intermediate to those of polyion complex and HPMC matrix tablets; water molecules were capable of penetrating throughout the tablets and relatively high diffusivity was similar to that in the polyion complex tablet, whereas like the HPMC matrix tablet, it was well swollen. This study succeeded in characterizing the tablet hydration process. MRI provides profound insight into the state of water molecules in hydrating tablets; thus, it is a useful tool for understanding drug release mechanisms at a molecular level.     

The chip firing game onn-cycles

Spencer introduced a chip firing game on a line, which was generalized by Björner, Lovasz and Shor to graphs. This paper characterizes those configurations which may be repeated in a game, and analyzes the game forn-cycles.This research was funded by NSERC operating grants.     

Synthesis of endo-(3-azabicyclo[3.1.0]hex-6-yl)-methanol and derivatives as new geometric/charge mimics of glycosyltransfer transition states

The syntheses of azabicyclo[3.1.0]hexane transition state (TS) analogs are described. Cyclopropanation of N-Boc-3-pyrroline with ethyl diazoacetate afforded a 1.6:1 exo/endo ratio of the resulting ester. Reduction of the endo-isomer with LiAlH₄ yielded the alcohol which was phosphorylated, or iodinated to provide access to aglycon containing TS analogs.     

A convenient stereoselective synthesis of cationic (η3-allyl)iron tetracarbonyl complexes

Allylic alcohols have been found to react with Fe₂(CO)₉ in ether to afford after addition of HBF₄/acetic anhydride, the corresponding (η³-allyl)Fe(CO)₄⁺BF₄^?- species (I) in moderate to good yields. The geometry of the starting alcohol is retained in the product complex; thus E-crotyl and -cinnamyl alcohols led to anti-substituted complexes, whereas the corresponding Z-alcohols produced syn-complexes.     

Evidence for Superconductivity in Nb2SC0.90 Carbosulfide

Abstract

Evidence for bulk superconductivity in Nb₂SC_0.90 carbosulfide is presented. Diamagnetic volume fraction of Nb₂SC_0.90 was precisely determined with low applied magnetic fields which were corrected by 6N lead rod as an internal standard. Based on magnetic field dependence of magnetic moment at several constant temperature's below T_C = 5 K, Nb₂SC_0.90 is found to be a type II superconductor with relatively high H _C2 and low H_C1.     

The important role of crystallinity and amylose ratio in thermal stability of starches

Journal of Thermal Analysis and Calorimetry - The thermal features of potato, banana, corn and cassava starches were correlated with structural properties. These starches were characterized by SEM,...