A.C. susceptibility measurements in the presence of D.C. magnetic fields in CoGa alloys — A cluster spin glass system

Low field a.c. susceptibility measurements in the presence of large d.c. magnetic fields are reported on Co_xGa_1?x alloys (x = 0.585, 0.60 and 0.63), a cluster spin glass system, in the temperature range of 77 to 500 K. A peak in the a.c. susceptibility is observed in each case. The peak position shifts towards lower temperatures with increasing d.c. magnetic fields. In conjunction with the zero field NMR measurements reported earlier, these results may be taken to imply the existence of a continuous spectrum of freezing temperatures — cluster with highest anisotropy field having the lowest freezing temperature.     

Computational identification of novel piperidine derivatives as potential HDM2 inhibitors designed by fragment-based QSAR,molecular docking and molecular dynamics simulations

Tumor suppressor protein p53 maintains integrity of genome and regulates the genes responsible for DNA repair mechanism, apoptosis as well as cell cycle and growth arrest. As with murine double minute 2 (MDM2), the human homolog HDM2 is a principal cellular antagonist of p53. In unstressed cells, cellular levels of p53 and HDM2 are maintained in an autoregulatory manner in which both mutually control cellular levels of each other. About half of the human cancers express wild-type p53 protein that is antagonized by over-expressed HDM2. Restoring p53 function via HDM2 antagonists is a leading therapeutic approach for treating a variety of tumors. In this study, we have developed a novel statistically sound group-based QSAR (GQSAR) model using piperidine-derived compounds that have been validated experimentally to inhibit p53–HDM2 interaction. On the basis of developed GQSAR model, a combinatorial library of molecules was prepared and its activity was predicted. These molecules were then docked to HDM2, and two top-scoring molecules possessing a binding energy of ?6.639 and ?6.305 kcal/mol were selected for further study. These molecules and their binding poses were analyzed further via molecular dynamic simulations. In this study, we report two lead compounds as potent HDM2 inhibitors and also provide an insight into mechanism of interaction of the lead compounds to HDM2 target.

     

Microstress,strain, band gap tuning and photocatalytic properties of thermally annealed and Cu-doped ZnO nanoparticles

ZnO nanoparticles and Cu-doped ZnO nanoparticles were prepared by co-precipitation method. Also, a part of the pure ZnO nanoparticles were annealed at 750 °C for 3, 6, and 9 h. X-ray diffraction studies were carried out and the lattice parameters, unit cell volume, interplanar spacing, and Young’s modulus were calculated for all the samples, and also the crystallite size was found using the Scherrer method. X-ray peak broadening analysis was used to estimate the crystallite sizes and the strain using the Williamson–Hall (W–H) method and the size–strain plot (SSP) method. Stress and the energy density were calculated using the W–H method assuming different models such as uniform deformation model, uniform strain deformation model, uniform deformation energy density model, and the SSP method. Optical absorption properties of the samples were understood from their UV–visible spectra. Photocatalytic activities of ZnO and 5 % Cu-doped ZnO were observed by the degradation of methylene blue dye in aqueous medium under the irradiation of 20-W compact fluorescent lamp for an hour.     

Spectrophotometric determination of thorium in standard samples and monazite sands based on the floated complex of thorium with N-hydroxy-N,N′-diphenylbenzamidine and thorin

A selective and sensitive spectrophotometric method for the determination of Th(IV) has been based on the reaction with thorin and subsequent extraction of the red-orange coloured complex with N-hydroxy-N,N'-diphenylbenzamidine (HDPBA) in benzene as floated complex at pH 2.2. The complex in ethanol exhibits a maximum absorbance at 495 nm, with a molar absorptivity of 6.0x10(4) l mol(-1) cm(-1), with a Sandell's sensitivity of 3.9x10(-3) microg cm(-2). The method follows Beer's law up to 3.0 microg Th(IV) ml(-1). None of the common cations and anions tested interfere. The detection limit of the method is 0.04 microg Th(IV) ml(-1), the RSD (n=10) is 1.4%. The method has been successfully employed for the determination of thorium in various standard and monazite samples.     

Production of C2H4Cl+ by dissociative photoionization of weak molecular complexes in C2H4+HCl mixtures

The photoionization efficiency (PIE) spectrum from 600 to 1200 Å for the production of the ion C₂H₄Cl⁺ by dissociative photoionization of the products of room-temperature jet expansions of a 1:4 mixture of C₂H₄ and HCl was measured at several nozzle pressures. The results were resolved into the PIE yield curve for the heterodimer process C₂H₄·HCl+hv→C₂H₄Cl⁺+H+e. This reaction is necessarily characterized by a large change in geometry between neutral complex and ionic product. The observed spectrum exhibits an unusual and conspicuous peak at 15.2 eV that is characterized by a sharp cutoff to the high energy side. This feature points to the onset of strongly nonstatistical channels for the production of C₂H₄Cl⁺ at this energy such that product formation proceeds through very few states. The observed onset of C₂H₄Cl⁺ at 11.92±0.24 eV is 17±6 kcal mol^?1 above the true threshold. An important conclusion is that at all energies above the onset the yield of dissociative ionization of the heterodimer to the cation C₂H₄Cl⁺ is determined by dynamical factors.     

Solid phase synthesis of 2-aminoquinazoline-based compounds

A versatile method for the solid-phase synthesis of 2-aminoquinazoline-based derivatives, 3-substituted-3,4-dihydroquinazolin-2-amines and imidazoquinazolines, has been developed. They were obtained by treating the amino group of polymer-linked amino acids with 2-nitrobenzaldehyde followed by reduction of the nitro group to an amine. Cyclization of the resulting immobilized intermediates with cyanogen bromide followed by acidic/basic cleavage yielded the desired quinazoline-based compounds in high yields and purities.     

Diisopropyl tartrate (E)-γ-(dimethylphenylsilyl)allylboronate, a chiral allylic alcohol β-carbanion equivalent for the enantioselective synthesis of 2-butene-1,4-diols from aldehydes

An enantioselective synthesis of 4-substituted (E)-2-buten-1,4-diols is described. The method involves the reaction of aldehydes with the chiral PhMe₂Si- substituted allylboronate3 followed by epoxidation (dimethyl dioxirane) and acid catalyzed Petersen rearrangement of the intermediate epoxysilanols.     

Studies in fluorinated 1,3-diketones and related compounds Part XV. Synthesis and spectroscopic studies of some new fluorinated monothio-1,3-diketones

Six new polyfluorinated monothio-l,3-diketones have been synthesized from the corresponding fluorinated aceto- phenones and appropriate 0-alkyl thioesters in the presence of sodamide. All these monothio-1,3-diketones are characterized by I.R. and ¹H N.M.R. spectral studies.     

A photoionization study of the van der Waals molecule C2H4 · HCl

The dissociation energy of the C₂H₄ · HCl van der Waals complex was determined to be 3.18±0.73 kcal mol^?1 by a dissociative photoionization technique. C₂H₄ · HCl was produced by free expansion of a 1:4 mixture of C₂H₄ in HCl and the clusters were ionized with tunable synchrotron radiation. The photoionization efficiency function of (C₂H₄ · HCl)⁺ from C₂H₄ · HCl was determined between 600 and 1,300 Å and the onset for (C₂H₄ · HCl)⁺ was established as 1,163±2 Å = 10.66±0.02 eV; these values give ΔH _f ⁰ (C₂H₄ · HCl) = ?10.7±0.7 kcal mol^?1 and ΔH _f ⁰ (C₂H₄·HCl⁺)=235.1±0.9 kcal mol^?1. A complex ion dissociation energyD ₀(C₂H₄ · HCl⁺) = ?0.3±0.9 kcal mol^?1 was calculated from the results. The major features on the PIE curve for C₂H₄ · HCl⁺ can be analyzed in terms of the known energetic features of C₂H ₄ ⁺ and HCl. An extended energy diagram for the C₂H₄ + HCl system is presented.