One-pot Synthesis,Crystal Structures and Antimicrobial Activities of Two New 1,4-Disubstituted 1,2,3-Triazole-4-Carboxylates

Two new 1,4-disubstituted 1,2,3-triazoles-4-carboxylates were synthesized via click reaction. Compound 1a was synthesized by the interaction of 6-nitro-tetrazolo[1.5-a]-pyridine with ethyl propynoate at room temperature in the presence of Cu(OAc)2 as a catalyst and THF as solvent. Compound 1b was also synthesized by the same manner except that tert-butyl propionate, instead of ethyl propynoate, was used. The compounds were characterized by IR, 1H-NMR, 13C-NMR and single-crystal X-ray diffraction analysis. Compound 1a(C10H9N5O4) crystallizes in the triclinic system, space group P1 with a = 5.0894(9), b = 8.9834(13), c = 13.089(2) ?, α= 83.041(7), β= 80.256(7), γ=87.296(8)°, V = 585.24(16)?3, Z = 2, Mr = 263.22, crystal size(mm) = 0.37 × 0.20 ×0.18,(I 2σ(I)) = 8557, 2493, 1229, Rint = 0.057. Compound 1b(C12H13N5O4) crystallizes in the monoclinic system, space group P21/c with a = 6.8854(5), b = 21.783(2), c = 9.3986(8) ?,β = 93.239(4)°, V = 1407.4(2)?3, Z = 4, Mr = 291.27, crystal size(mm) = 0.38 × 0.22 × 0.20,(I 2σ(I)) = 11842, 3172, 1866, Rint = 0.047. Antimicrobial assay results showed that the title compounds display excellent activities to different bacterial and fungal strains.     

Antihydrophobic solvent effects: an experimental probe for the hydrophobic contribution to enzyme-inhibitor binding

The hydrophobic component to the binding affinities of one acyclic phosphinate (4) and three macrocyclic phosphonamidate inhibitors (1-3) to the zinc peptidase thermolysin was probed by varying the solvent composition. Increasing the percentage of ethanol in the buffer solution over the range 0-9% increases the inhibition constants, K(i), by up to an order of magnitude. This approach represents an experimental method for distinguishing solvation from conformational or other effects on protein-ligand binding. The size of the "antihydrophobic effect" is correlated with the amount of hydrophobic surface area sequestered from solvent on association of the inhibitor and enzyme, although it is attenuated from that calculated from the surface tension of ethanol-water mixtures. The results are consistent with the Lum-Chandler-Weeks explanation for the size dependence of the hydrophobic effect.     

Aqueous dispersions of single-wall and multiwall carbon nanotubes with designed amphiphilic polycations

Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting.     

Radiation-induced graft polymerization of acrylic acid onto fluorinated polymers. I. Kinetic study on the grafting onto poly(tetrafluoroethylene-ethylene) copolymer

Direct radiation-induced grafting of aqueous acrylic acid (AAc) onto poly(tetrafluoroethylene-ethylene) (ET) film has been studied. The effect of grafting conditions such as monomer concentration, exposure dose, dose rate, and film thickness on the grafting yield was investigated. The dependence of the grafting rate on monomer concentration was found to be 1.2 order. The dependence of the grafting rate on dose rate was found to be 0.6 order regardless of the film thickness. The relationship between the grafting rate and film thickness gave a negative first-order dependence. The results suggest that the grafting process is mainly controlled by monomer diffusion, and it was concluded that this grafting system proceeded by the front mechanism. The swelling behavior increases linearly with degree of grafting. The electrical conductivity and mechanical properties for the trunk and grafted polymer were investigated at different irradiation doses in air and under vacuum irradiations. © 1992 John Wiley & Sons, Inc.     

Sorption of divalent metal ions on CrPO4

The divalent metal ion sorption (Cu(2+), Cd(2+), Ni(2+), and Pb(2+)) on chromium phosphate (CrPO(4)) was studied as a function of pH, temperature, and concentration of metal ions. The sorption of metal ions is observed to increase with the increase in pH, temperature, and concentration of metal ions in solution. The mechanism of sorption is found to be the exchange of the hydrolyzed metal cations with the protons from solid at high temperature. The sorption at low temperature is found to be accompanied by the precipitation of the corresponding metal phosphates such as Pb(3)(PO(4))(2).     

Analytical and numerical solution for viscous dissipation effect on the heat transfer in a deformable channel

In this paper, shooting method and homotopy perturbation technique are applied for the flow analysis of temporal energy transport in a deformation channel with isothermal walls. An incompressible viscous fluid fills the space inside the channel. Analytical and numerical solutions are developed for the momentum and energy equations. The viscous dissipation effects are taken into account. Graphs for pertinent flow parameters are sketched and discussed. Comparison between the analytical and numerical solutions indicates an excellent agreement. It is noticed that behaviors of Prandtl and Eckert numbers on the temperature are qualitatively similar. Copyright © 2011 John Wiley & Sons, Ltd.     

Complete NMR assignments of bioactive rotameric (3 → 8) biflavonoids from the bark of Garcinia hombroniana

The genus Garcinia is reported to possess antimicrobial, anti‐inflammatory, anticancer, hepatoprotective and anti‐HIV activities. Garcinia hombroniana in Malaysia is used to treat itching and as a protective medicine after child birth. This study was aimed to isolate the chemical constituents from the bark of G. hombroniana and explore their possible pharmacological potential. Ethyl acetate extract afforded one new (1) and six (2–7) known 3 → 8 rotameric biflavonoids. Their structures were elucidated by UV, IR and NMR (1D and 2D) spectroscopy together with electron ionization/ESI mass spectrometric techniques and were identified as (2R, 3S) volkensiflavone‐7‐O‐rhamnopyranoside (1), volkensiflavone (2), 4″‐O‐methyl‐volkensiflavone (3), volkensiflavone‐7‐O‐glucopyranoside (4), morelloflavone (5), 3″‐O‐methyl‐morelloflavone (6) and morelloflavone‐7‐O‐glucopyranoside (7). The absolute configuration of compound 1 was assigned by circular dichroism spectroscopy as 2R, 3S. The coexistence of conformers of isolated biflavonoids in solution at 25 °C in different solvents was confirmed by variable temperature NMR studies. At room temperature (25 °C), compounds 1–7 exhibited duplicate NMR signals, while at elevated temperature (90 °C), a single set of signals was obtained. Compound 5 showed significant in vitro antioxidant activities against 1,1‐diphenyl‐2‐picrylhydrazyl and 2,2′‐azino‐bis‐3‐ethyl benzthiazoline‐6‐sulfonic acid radicals. The antibacterial studies showed that compounds 5 and 6 are the most active against Staphylococcus aureus, Bacillus subtilis and Escherichia coli. Compounds 3 and 6 also showed moderate antituberculosis activity against H₃₈Rv. Based on the research findings, G. hombroniana could be concluded as a rich source of flavanone–flavone (3 → 8) biflavonoids that exhibit rotameric behaviour at room temperature and display significant antioxidant and antibacterial activities. Copyright © 2014 John Wiley & Sons, Ltd.