Studies on the interaction of diacetylcurcumin with calf thymus-DNA

Ongoing research on curcumin and its structural derivatives are a subject of growing interest because of their demonstrated biological properties. Diacetylcurcumin (DAC), a synthetic derivative of natural non-toxic curcumin has been shown to affect a host of activities ranging from wound healing to life threatening diseases like AIDS, cancer etc. The interaction of diacetylcurcumin (DAC) with calf thymus-DNA (ct-DNA) has been investigated by spectroscopic and viscometric techniques. The fluorescence intensity of DAC was quenched by ct-DNA. The mean binding constant obtained from the spectroscopic techniques was 3.97 ± 0.31 × 10⁵ M⁻¹. Circular dichroism studies did not reveal any unwinding of the DNA helix on interaction with DAC, implying no conformational changes. The binding mode was analyzed by competitive binding between ethidium bromide (EB) and DAC for ct-DNA and also by viscometric studies. DAC was found to be a minor groove binder with a preference for the A-T region compared to the G-C region. This was substantiated by displacement studies with Hoechst 33258, a known minor groove binder. Docking studies were found to corroborate the experimental results.     

Synthesis and Antibacterial Activities of Amphiphilic Neomycin B-based Bilipid Conjugates and Fluorinated Neomycin B-based Lipids

Investigating the effect of lipid hydrophobicity on the activity of amphiphilic neomycin B conjugates, six polycationic amphiphiles (PAs) were created. Four of the new compounds incorporated either palmitic or arachidic di-lipid lysine tails, while two had single fluorinated undecanoic acid tails. The basicity of half of the compounds was increased through the incorporation of six guanidine moieties, in order to assess the effect of base strength on antimicrobial activity. A panel of ten bacteria was used for the testing, with seven strains obtained from the American Type Culture Collection series and three clinical isolates from Canadian Intensive Care Units. When compared to previous results with hydrocarbon monolipids the PAs all compounds were found to have reduced activity, though the hemolytic activity of the compounds with fluorinated tails was sharply reduced, with only a moderate reduction in antimicrobial activity.     

Effect of Mg substitution on electromagnetic properties of (Ni0.25Cu0.20Zn0.55)Fe2O4 ferrite prepared by auto combustion method

The ferrite compositions of (Ni_0.25−xMg_xCu_0.2Zn_0.55)Fe₂O₄ with x=0.0$x=0.0$, 0.07, 0.13, 0.18, and 0.25 were synthesized through nitrate-citrate auto-combustion method. The as-burnt powders showed the presence of crystalline cubic spinel ferrite with about 19–22 nm crystallite sizes. The resultant powders were calcined at 700 °C/2 h and pressed ferrites were sintered at 950 °C/4 h. The initial permeability, magnetic loss and AC resistivity were measured in the frequency range 10 Hz–10 MHz. The permeability and AC resistivity were found to increase and the magnetic loss decreased with Mg substitution for Ni, up to x=0.18$x=0.18$. The very high permeability in the composition x=0.18$x=0.18$, was due to better densification, lower magnetostriction constant and inner stresses, etc. The AC resistivity of the composition was also highest. The composition would be better than NiCuZn-based material for more miniaturization of multi layer chip inductor.     

Synthesis,structural analysis,and visualization of poly(2‐ethynyl‐9‐substituted carbazole)s and poly(3‐ethynyl‐9‐substituted carbazole)s containing chiral and achiral minidendritic substituents

The synthesis of 2‐ethynyl‐9‐substituted carbazole and 3‐ethynyl‐9‐substituted carbazole monomers containing first‐generation chiral and achiral dendritic (i.e., minidendritic) substituents, 2‐ethynyl‐9‐[3,4,5‐tris(dodecan‐1‐yloxy)benzyl]carbazole (2ECz), 3‐ethynyl‐9‐[3,4,5‐tris(dodecan‐1‐yloxy)benzyl]carbazole (3ECz), 2‐ethynyl‐9‐{3,4,5‐tris[(S)‐2‐methylbutan‐1‐yloxy]benzyl}carbazole (2ECz*), and 3‐ethynyl‐9‐{3,4,5‐tris[(S)‐2‐methylbutan‐1‐yloxy]benzyl}carbazole (3ECz*), is presented. All monomers were polymerized and copolymerized by stereospecific polymerization to produce cis‐transoidal soluble stereoisomers. A structural analysis of poly(2ECz), poly(2ECz*), poly(3ECz), poly(3ECz*), poly(2ECz*‐co‐2ECz), and poly(3ECz*‐co‐3ECz) by a combination of techniques, including ¹H NMR, ultraviolet–visible, and circular dichroism spectroscopy, thermal optical polarized microscopy, and X‐ray diffraction experiments, demonstrated that these polymers had a helical conformation that produced cylindrical macromolecules exhibiting chiral and achiral nematic phases. Individual chains of these cylindrical macromolecules were visualized by atomic force microscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3509–3533, 2002     

Outer‐sphere reduction of hexacyanoferrate(III) by enolizable and nonenolizable aldehydes in alkaline medium

Outer‐sphere reduction of hexacyanoferrate(III) by some enolizable/nonenolizable aldehydes (viz., aliphatic, heterocyclic, and aromatic aldehydes) in alkaline medium has been studied spectrophotometrically at λ_max = 420 nm. The reactions are first order each in [aldehyde] and [Fe(CN)₆^3?]. The rate increases with an increase in [OH^?] in the oxidation of aliphatic and heterocyclic aldehydes, whereas it is independent of [OH^?] in the reaction with aromatic aldehydes. The intervention of free radicals in the reaction mixture was carried out using both acrylonitrile and acrylamide scavenger in two different experiments. The kinetic results indicate that the oxidation of benzaldehyde in aqueous medium proceeds at a slower rate than the aliphatic aldehydes (other than formaldehyde) and furfural. The values of third‐order rate constant (k₃) at 308 K in the oxidations of some aliphatic aldehydes and furfural follow the order (CH₃)₂CH? > CH₃CH₂? > CH₃? > C₄H₃O? > H? . The rate constants correlate with Taft's σ* value, the reaction constant being negative (–9.8). The pseudo–first‐order rate constants in the oxidations of benzaldehyde and substituted benzaldehydes follow the order ? NO₂ > ? H > ? Cl > ? OCH₃. The Hammett plot is also linear with a ρ value (0.6488) for meta‐ and para‐substituted benzaldehydes. The kinetic isotope effect for benzaldehyde (k_H/k_D = 1.93 at 303 K) was obtained. The rate‐determining step is the outer‐sphere formation of Fe(CN)₆^4? and free radicals, which is followed by the rapid oxidation of free radicals by Fe(CN)₆^3? to give products. The kinetic data and hence thermodynamic parameters have been used to distinguish enolizable and nonenolizable aldehydes. An attempt has also been made to correlate kinetic data with hydration equilibrium constants of some aliphatic aldehydes. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 494–505, 2012     

Low dielectric constant polyimide nanomats by electrospinning

The proper combination of material (i.e. fluorinated polyimides) and processing technique (electrospinning) could lead to the formation of polyimides with low dielectric constant, high thermo‐oxidative stability and glass transition temperature, and high hydrophobicity. The polyimides in this work were based on 4, 4‐bis [3′‐trifluoromethyl‐4′ (4′‐amino benzoxy) benzyl] biphenyl (Q) and various fluorinated and non‐fluorinated dianhydrides namely benzene‐1,2,4,5‐tetracarboxylic dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride, benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride, and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Processing of the polyimides was carried out in poly(amic acid) stage by two different methods—electrospinning and solution casting for comparison purposes. The processing of polyimides by electrospinning led to enhancement in mechanical properties (dianhydride‐structure dependent) and hydrophobicity without sacrificing thermo‐oxidative stability and glass transition temperatures significantly. Also, low dielectric constants (as low as 1.43) could be attained by suitable combination of dianhydride (6FDA) with 4, 4‐bis [3′‐trifluoromethyl‐4′ (4′‐amino benzoxy) benzyl] biphenyl diamine. Copyright © 2011 John Wiley & Sons, Ltd.     

Kinetic and mechanistic studies on the substitution of aqua ligands from <Emphasis Type="Italic">cis</Emphasis>-diaqua-<Emphasis Type="Italic">bis</Emphasis>-(bypyridyl)-ruthenium(II) ion by vic-dioximes

Kinetics of aqua ligand substitution from cis-[Ru(bpy)₂(H₂O)₂]²⁺ by three vicinal dioximes, namely dimethylglyoxime (L¹H), 1,2-cyclohexane dionedioxime (L²H) and α-furil dioxime (L³H) have been studied spectrophotometrically in the 45–60 °C temperature range. The rate constants increase with increasing dioxime concentration and approach a limiting condition. We propose the following rate law for the reaction in the 3.5–5.5 pH range: where k ₂ is the interchange rate constant from outer sphere to inner sphere complex and K _E is the outer sphere association equilibrium constant. Activation parameters were calculated from the Eyring plots for all three systems: ΔH ^≠ = 59.2 ± 8.8, 63.1 ± 6.8 and 69.7 ± 8.5 kJ mol⁻¹, ΔS ^≠ = −122 ± 27, −117 ± 21 and −99 ± 26 J K⁻¹ mol⁻¹ for L¹H, L²H and L³H, respectively. An associative interchange mechanism is proposed for the substitution process. Thermodynamic parameters calculated from the temperature dependence of the outer sphere association equilibrium constants give negative ΔG ⁰ values for all the systems studied at all the temperatures (ΔH ⁰ = 30.05 ± 2.5, 18.9 ± 1.1 and 11.8 ± 0.2 kJ mol⁻¹; ΔS ⁰ = 123 ± 8, 94 ± 3 and 74 ± 1 J K⁻¹ mol⁻¹ for L¹H, L²H and L³H, respectively), which also support our proposition.     

Growth and structure of Pd films on ZnO(0001)

The growth and structure of Pd films on ZnO(0001) were investigated using high resolution electron energy loss spectroscopy, x-ray photoelectron spectroscopy, and low energy electron diffraction. Vapor deposited Pd films at 300 K were found to follow a two-dimensional (2D) island growth mode, in which 2D metal islands are formed up to a critical coverage at which point growth occurs primarily in a layer-by-layer fashion on top of the islands. Heating to only 350 K was found to be sufficient to induce partial agglomeration of Pd films into three-dimensional particles. In addition to causing further agglomeration into particles, heating to 700 K resulted in partial reduction of the ZnO surface and the formation of a PdZn alloy.     

Revisiting the reaction of β-chloroacroleins with 2-aminophenol: a new observation

The reaction of β-chloroacrolein with 1 equiv of 2-aminophenol in DMF proceeds smoothly to afford 11-hydroxy derivative of chromenoquinoline in good yield. This single pot method allows for a rapid access to a variety of chromenoquinolines or oxepinoquinolines depending on the nature of β-chloroacrolein used. The structures were established by spectroscopic data and further confirmed by X-ray diffraction analysis. A plausible mechanism for this reaction has been proposed. The reaction seemed to proceed via a chloroimine species, whose intermediacy has been established, followed by the construction of the fused quinoline ring.