An efficient reusable silver-exchanged tungstophosphoric acid heterogeneous catalyst for solvent-free intermolecular hydroamination of alkynes

Hydroamination of alkynes with both aromatic and aliphatic amines proceeds efficiently in the presence of silver-exchanged tungstophosphoric acid (AgTPA) catalyst under solvent-free conditions to afford ketimines in excellent yields.     

The tumor inhibitor and antiangiogenic agent withaferin A targets the intermediate filament protein vimentin

The natural product withaferin A (WFA) exhibits antitumor and antiangiogenesis activity in vivo, which results from this drug's potent growth inhibitory activities. Here, we show that WFA binds to the intermediate filament (IF) protein, vimentin, by covalently modifying its cysteine residue, which is present in the highly conserved alpha-helical coiled coil 2B domain. WFA induces vimentin filaments to aggregate in vitro, an activity manifested in vivo as punctate cytoplasmic aggregates that colocalize vimentin and F-actin. WFA's potent dominant-negative effect on F-actin requires vimentin expression and induces apoptosis. Finally, we show that WFA-induced inhibition of capillary growth in a mouse model of corneal neovascularization is compromised in vimentin-deficient mice. These findings identify WFA as a chemical genetic probe of IF functions, and illuminate a potential molecular target for withanolide-based therapeutics for treating angioproliferative and malignant diseases.     

Fluorescence quenching of 3-methyl 7-hydroxyl Coumarin in presence of acetone

Fluorescence quenching of 3-methyl 7-hydroxyl Coumarin in prescence of the acetone is reported here. It was found that the quenching observed was of dynamic nature. It is also observed that quenching of the fluorescence of the indicator had a full reversiblity. As it has a full reversiblity, a novel optical sensor for acetone can be constructed on this quenching.     

Fourier transform infrared and Raman spectral assignments and analysis of 7-amino-4-trifluoromethylcoumarin

FTIR and FT-Raman spectra of 7-amino-4-trifluoromethylcoumarin (ATMC) have been recorded in the range 4000-400 and 3500-100 cm(-1), respectively, using Bruker IFS 66 V spectrometer. A detailed vibrational analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions, relative intensities, fundamentals, overtones and combination bands. With hope of providing more and effective information on the fundamental vibrations, a normal co-ordinate analysis has been performed by assuming C(S) point group symmetry. The simple valance force field (SVFF) has been employed in normal co-ordinate analysis and to calculate the potential energy distribution (PED) for each fundamental vibration are reported. The PED contribution to each of the observed frequencies shows the reliability and precision of the spectral analysis.     

Mesoscale simulations of the behavior of charged polymer brushes under normal compression and lateral shear forces

Dissipative particle dynamics (DPD) was used to investigate the behavior of two opposing end-grafted charged polymer brushes in aqueous media under normal compression and lateral shear. The effect of polymer molecular weight, degree of ionization, grafting density, ionic strength, and compression on the polymer conformation and the resulting shear force between the opposing polymer layers were investigated. The simulations were carried out for the poly(tert-butyl methacrylate)-block-poly(sodium sulfonate glycidyl methacrylate) copolymer, referred as PtBMA-b-PGMAS, end-attached to a hydrophobic surface for comparison with previous experimental data. Mutual interpenetration of the opposing end-grafted chains upon compression is negligible for highly charged polymer brushes for compression ratios ranging from 2.5 to 0.25. Under electrostatic screening effects or for weakly charged polymer brushes, a significant mutual interpenetration was measured. The variation of interpenetration thickness with separation distance, grafting density, and polymer size follows the same scaling law as the one observed for two opposing grafted neutral brushes in good solvent. However, compression between two opposing charged brushes results in less interpenetration relative to neutral brushes when considering equivalent grafting density and molecular weight. The friction coefficient between two opposing polymer-coated surfaces sliding past each other is shown to be directly correlated with the interpenetration thickness and more specifically to the number of polymer segments within the interpenetration layer.     

Monoids and Cuspidal Group Characters

Let M be a finite monoid with unit group G. By the work of Munn and Ponizovski, the irreducible complex representations of M are classified according to which J-class (apex) they come from. Consider the irreducible representations of M with apex . These representations restrict to representations of G, whose components we view as coming from J-classes below G. The remaining irreducible representations (and their characters) of G are called cuspidal. We show that an irreducible character of G is cuspidal if and only if for all idempotents , where .     

Rayleigh–Taylor Instability of Rotating Oldroydian Viscoelastic Fluids in Porous Medium in Presence of a Variable Magnetic Field

The instability of the plane interface between two oldroydian viscoelastic superposed fluids in the presence of uniform rotation and variable magnetic field in porous medium is considered. For potentially stable configuration, the system is found to be stable for disturbances of all wave numbers. The magnetic field succeeds in stabilizing certain wave-number range, which were unstable in the absence of magnetic field and rotation for the potentially unstable configuration. Sub cases of magnetic free and rotation free configurations are also considered, separately.     

What Difference Does a Methyl Group Make: Pentamethylbenzene?

The crystal structure of pentamethylbenzene has been obtained for the first time with the use of synchrotron radiation, whilst the low‐energy spectrum of lattice dynamics, dominated by the methyl group torsions, was obtained using inelastic neutron scattering. The effect of symmetry lowering by the removal of a single methyl group relative to hexamethylbenzene has been investigated, including the role that this plays in the charge‐transfer characteristics of complexes formed with tetracyanoethylene.     

One‐Pot Protection‐Glycosylation Reactions for Synthesis of Lipid II Analogues

(2,6‐Dichloro‐4‐methoxyphenyl)(2,4‐dichlorophenyl)methyl trichloroacetimidate ( 3 ) and its polymer‐supported reagent 4 can be successfully applied to a one‐pot protection‐glycosylation reaction to form the disaccharide derivative 7 d for the synthesis of lipid II analogues. The temporary protecting group or linker at the C‐6 position and N‐Troc protecting group of 7 d can be cleaved simultaneously through a reductive condition. Overall yields of syntheses of lipid II ( 1 ) and neryl‐lipid II N^ε‐dansylthiourea are significantly improved by using the described methods.