Structural deformation monitored by vibrational properties and orbital modeling in (Pb,Sm)TiO3 systems

Pb_1−xSm_xTiO₃ (PST) powders with x varying from 0 to 0.1 were obtained by the polymeric precursor method, a soft chemical route. The vibrational properties relating tetragonal to pseudo-cubic phase transition were studied by Raman spectroscopy. The results obtained showed that the phase transition is extremely dependent upon the samarium content and presents a diffuse behavior. Monitoring of the oxygen 2p and titanium 3d orbitals was performed by the periodic mechanical quantum method, revealing the changes that occur with the distribution and contribution of the hybrid orbitals due to the samarium influence.     

Li‐doped nanosized TiO2 powder with enhanced photocalatylic acivity under sunlight irradiation

This work reports on the synthesis of Li‐doped TiO₂ nanoparticles using the sol–gel process and solid‐state sintering, and investigates their potential use as a photocatalyst for degradation under sunlight excitation of different organic model compounds in aqueous solution. The structure of the nanocrystals was examined by X‐ray diffraction, UV‐vis ground state diffuse reflectance absorption spectra and X‐ray photoelectron emission spectroscopy. Results showed that samples prepared by sol–gel process and calcined at 400 °C are composed of a mixture of anatase and rutile phases, in contrast to the one prepared by solid‐state sintering, which exhibits an anatase phase with Li being involved in a spinel phase. The photocatalytic degradation of aqueous solutions of different aromatic compounds was successfully achieved under sunlight excitation in presence of Li‐doped TiO₂ prepared via sol–gel process. It was shown that the calcination temperature and the preparation mode greatly affect the photocatalytic efficiency. Copyright © 2010 John Wiley & Sons, Ltd.     

The bicyclic n,n'-diacylaminal: a new motif for molecular self-assembly

A cage-shaped N,N'-diacylaminal crystallizes from some aromatic solvents as "supramolecular chair cyclohexanes", squat cylindrical hexamers with approximate D3d symmetry containing two arene molecules, and from other aromatic and nonaromatic solvents as infinite tapes. A homologous diacylaminal crystallizes only as an infinite tape. The hexamers represent the first examples of cyclic hexamers held together by %@mt;sys@%%@bold@%R%@rsf@%%@sx@%2%@be@%2%@sxx@%%@fn;(;vis;full;auto@%8%@fnx;);vis;full@%-type%@mx@% hydrogen bonds in which the hydrogen-bonded atoms are not coplanar. The diacylaminal represents a new supramolecular synthon, one perhaps more suited to the design of three-dimensional architectures.     

A method for bioconjugation of carbohydrates using Diels-Alder cycloaddition

Diels-Alder-type cycloaddition of an electronically matched pair of saccharide-linked conjugated dienes and a dienophile-equipped protein gives neoglycoproteins at ambient temperature in pure water with a reaction half-life of approximately 2 h. Uncoupled saccharides can be recovered by diafiltration with complete conservation of the diene moiety, thus allowing their repeated use. The procedure described is the first for creating a carbon-carbon covalent bond in the bioconjugation step between a saccharide and a protein.     

Porphyrin-containing molecular capsules: metal mediated dimerization of a bis-porphyrin cavity

[reaction] A self-complementary V-shaped bis-porphyrin cavity has been synthesized that is capable of dimerization to form a capsule structure. Self-assembly of the dimer occurs via metal ion coordination and produces an internal volume for guest encapsulation.     

Dysregulation of Na+/K+ ATPase by amyloid in APP+PS1 transgenic mice

Background  

The pathology of Alzheimer's disease (AD) is comprised of extracellular amyloid plaques, intracellular tau tangles, dystrophic neurites and neurodegeneration. The mechanisms by which these various pathological features arise are under intense investigation. Here, expanding upon pilot gene expression studies, we have further analyzed the relationship between Na+/K+ ATPase and amyloid using APP+PS1 transgenic mice, a model that develops amyloid plaques and memory deficits in the absence of tangle formation and neuronal or synaptic loss.