Catalytic Approach for the Synthesis of bis‐Calixarenes

Three new tail‐to‐tail linked biscalix[6]arenes joined via ether linkages have been synthesized. These bis calix[6]arenes have been characterized by ¹H NMR, ¹³C NMR, and mass spectroscopy and elemental analysis.     

Polymerization and viscoelastic behavior of networks from a dual‐curing,liquid crystalline monomer

The network formation and viscoelastic behavior of a liquid crystalline monomer, whose structure includes both acrylate and acetylene reactive groups, have been studied. By combining both photo and thermal polymerization, the networks can be formed in two separate steps, with the initial photopolymerization dominated by acrylate crosslinking and subsequent thermal polymerization dominated by acetylene crosslinking. In addition, the monomer exhibits a liquid crystalline phase. Photopolymerization while in the liquid crystal phase locks in the molecular ordering. Dynamic mechanical analysis shows that networks formed from the liquid crystalline phase have lower crosslink densities and narrower distributions of molecular weights between crosslinks when compared to networks formed from the isotropic phase (and at higher polymerization temperatures). After thermal postcure at 250°C, the networks formed from the isotropic monomer have a 23% higher dynamic mechanical storage modulus (in the glassy state) than the networks formed from the liquid crystalline monomer. The thermally postcured networks have unusually high glass‐transition temperatures, which exceed 300°C. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1183–1190, 1999     

Novel mesoporous mixed Nb-M (M = V, Mo, and Sb) oxides for oxidative dehydrogenation of propane

Novel thermally stable mesoporous mixed metal Nb-M (M = V, Mo and Sb) oxides were synthesized in the presence of a nonionic Pluronic P123 surfactant. These oxides displayed promising pore structures and chemical compositions for selective oxidative functionalization of propane: high surface areas (up to 200 m2/g), large pore sizes (5-14 nm), and high pore volumes (up to 0.46 cm3/g). The oxidative dehydrogenation of propane to propylene over mesoporous mixed metal Nb-M oxides employed as a probe reaction suggested that the M component was dispersed as the molecular surface species and also formed a solid solution with NbOx in the inorganic walls of these mesoporous mixed metal oxides.     

A protocol for stripping and reprobing of Western blots originally developed with colorimetric substrate TMB

Western blotting is a widely used analytical technique for detection of specific protein(s) in a given sample of tissue/cell homogenate or extract. Both chemiluminescence (CL) and colorimetric detections can be used for imaging Western blots. Colorimetric substrates offer background free, sensitive, and clean imaging results directly on the blotted membrane and provides more accurate profile with respect to prestained marker. However, blots stained with colorimetric substrates cannot be reused since no stripping protocols have been reported for such blots, thus limiting their reuse for detection of another protein. In the present study, for the first time, we report a novel method of stripping Western blots developed with the colorimetric substrate TMB for detection of a low‐abundant protein and reprobing of these blots after stripping for detection of a more abundant protein through CL procedure. The stripping procedure utilizes a stripping buffer consisting of β‐mercaptoethanol, SDS, and Tris‐HCl and a washing buffer consisting of PBS added with 0.1% Tween‐20 involves a series of steps and facilitates accurate detection of the second protein (i.e., more abundant protein) in the stripped blot through CL. The protocol is reproducible and facilitates saving of precious clinical samples, in addition to saving cost and time as compared to the existing procedures.     

1,3‐dipolar cycloaddition reactions of 2‐substituted azomethine N‐oxides with N‐benzyl maleimides leading to the synthesis of stereoisomers

The azomethine N‐oxides ( 1 ) on reacting with N‐benzylmaleimide ( 2 ) provide a mixture of stereoisomers 2,3‐diphenyl‐5‐benzyl‐4H‐2,3,3a,5,6,6a‐hexahydropyrrolo[3,4‐d]isoxazole‐4,6–dione derivatives ( 3 ) in good yields. These isomers have been assigned cis and trans configurations ( 3‐A and 3‐B ) with respect to proton C₃‐H on the azomethinic carbon on the basis of their PMR and H‐NMR COSY data. The ratio between cis and trans isomers has been found to be dependent on substituents present at ortho position of C‐phenyl aldehydic moiety. The salient feature of these 1,3‐dipolar cycloaddition reactions lies in that the benzylic protons on N‐benzyl moiety suffer gem coupling, indicating magnetic nonequivalence. J. Heterocyclic Chem.,, (2012).     

An LC–MS–MS Method for the Simultaneous Quantitation of Acyclovir and Valacyclovir in Human Plasma

A simple, sensitive and selective LC–MS–MS method has been developed for the simultaneous determination of acyclovir and valacyclovir in human plasma. Acyclovir and valacyclovir in plasma were concentrated by solid phase extraction and chromatographed on a C18 column using a mobile phase of 0.1% formic acid: methanol (30:70% v/v). The method was validated over a linear range of 47–10,255 and 5–1,075 ng mL^?1 for acyclovir and valacyclovir respectively. The LOQs were 47.6 and 5.0 ng mL^?1. The validated method was applied for the quantitation of acyclovir and valacyclovir from plasma samples in a pharmacokinetic study.