Synthesis of new chrysin derivatives with substantial antibiofilm activity

Molecular Diversity - Multidrug resistance mechanism of microorganisms towards conventional antimicrobials nowadays faces a common health problem. So, searching and development of new...     

Study of silver nanoparticle-hemoglobin interaction and composite formation

Nanoscience is now an expanding field of research and finds potential application in biomedical area, but it is limited due to lack of comprehensive knowledge of the interactions operating in nano-bio system. Here, we report the studies on the interaction and formation of nano-bio complex between silver nanoparticle (AgNP) and human blood protein hemoglobin (Hb). We have employed several spectroscopic (absorption, emission, Raman, FTIR, CD, etc.) and electron diffraction techniques (FE-SEM and HR-TEM) to characterize the Hb-AgNP complex system. Our results show the Hb-AgNP interaction is concentration and time dependent. The AgNP particle can attach/come closer to heme, tryptophan, and amide as well aromatic amine residues. As a result, the Hb undergoes conformational change and becomes unfolded through the increment of β-sheet structure. The AgNP-Hb can form charge-transfers (CT) complex where the Hb-heme along with the AgNP involved in the electron transfer mechanism and form Hb-AgNP assembled structure. The electron transfer mechanism has been found to be dependent on the size of silver particle. The overall study is important in understanding the nano-bio system and in predicting the avenues to design and synthesis of novel nano-biocomposite materials in material science and biomedical area.     

Sulfonate protecting groups. Synthesis of O- and C-methylated inositols: d- and l-ononitol, d- and l-laminitol, mytilitol and scyllo-inositol methyl ether

Syntheses of d- and l-ononitol, d- and l-laminitol, mytilitol and scyllo-inositol methyl ether starting from myo-inositol are described. One or two of the myo-inositol 1,3,5-orthoformate hydroxyl groups were protected as tosylates. These mono or ditosylates served as key intermediates for the preparation of O- and C-methyl inositols. Racemic 2,4-di-O-tosyl-myo-inositol 1,3,5-orthoformate was resolved as its diastereomeric camphanates. Use of sulfonate groups for the protection of inositol hydroxyl groups resulted in substantial improvement in the overall yield of O- and C-methyl inositols.     

Influence of anions on the adsorption kinetics of salicylate onto alpha-alumina in aqueous medium

The adsorption kinetics of salicylate on alpha-alumina surfaces were studied at 25 degrees C and pH 6 in the presence of 0.05 mM concentration of different anions (Cl(-), Br(-), I(-), SCN(-), HCOO(-), CH(3)COO(-), S(2)O(2-)(3), CO(2-)(3), and SO(2-)(4)) as a function of time. The experimental data were significantly better fitted to a pseudo-second-order kinetics equation of nonlinear form in the entire time duration and are in excellent agreement with corresponding estimated values. Considering adsorption data for salicylate in the presence of Cl(-) as the face value, all the monovalent anions (Br(-), I(-), SCN(-), HCOO(-), CH(3)COO(-)) promote the adsorption of salicylate onto alpha-alumina surfaces while the divalent anions (S(2)O(2-)(3), CO(2-)(3), and SO(2-)(4)) have the reverse effect under similar conditions. DRIFT spectra of alpha-alumina treated with salicylate reveal that the symmetric peak nu(s)(COO(-)) is shifted by approximately 40 cm(-1) to a lower wavelength region, which implies that salicylate forms an inner-sphere complex with alpha-alumina surface in the presence of both mono- and divalent anions.     

The influence of functionality on the adsorption of p-hydroxy benzoate and phthalate at the hematite-electrolyte interface

Kinetics of adsorption of p-hydroxy benzoate and phthalate on hematite-electrolyte interface were investigated at a constant ionic strength, I = 5 x 10(-4) mol dm(-3), pH 5 and at three different temperatures. The state of equilibrium for the adsorption of p-hydroxy benzoate onto hematite surfaces was attained at 70 h, whereas it was 30 h for phthalate-hematite system. None of the three kinetics models (Bajpai, pseudo first order and pseudo second order) is applicable in the entire experimental time period; however, the pseudo second order kinetics model is considered to be better than the pseudo first order kinetics model in estimating the equilibrium concentration both the p-hydroxy benzoate-hematite and phthalate-hematite systems. The variation of adsorption density of p-hydroxy benzoate and phthalate onto hematite surfaces as a function of concentration of adsorbate was studied over pH range 5-9 at a constant ionic strength, I = 5 x 10(-4) mol dm(-3) and at constant temperature. The adsorption isotherms for both the systems were Langmuir in nature and the maximum adsorption density (Gamma(max)) of p-hydroxy benzoate is approximately 1.5 times more than that of phthalate on hematite at pH 5 and 30 degrees C in spite of an additional carboxylic group at ortho position in phthalate. This is due to the more surface area coverage by phthalate than that of p-hydroxy benzoate on hematite surface. The activation energy was calculated using Arrhenius equation and the activation energy for adsorption of p-hydroxy benzoate at hematite-electrolyte interface is approximately 1.8 times more than that of phthalate-hematite system. The negative Gibbs free energy indicates that the adsorption of p-hydroxy benzoate and phthalate on hematite surfaces is favourable. The FTIR spectra of p-hydroxy benzoate and phthalate after adsorption on hematite surfaces were recorded for obtaining the bonding properties of adsorbates. The phenolic nu(CO) appears at approximately 1271 cm(-1) after adsorption of p-hydroxy benzoate on hematite surfaces, which shifted by 10 cm(-1) to higher frequency region. The phenolic group is not deprotonated and is not participating in the surface complexation. The shifting of the nu(as)(COO-) and nu(s)(COO-) bands and non-dissolution of hematite suggest that the p-hydroxy benzoate and phthalate form outer-sphere surface complex with hematite surfaces in the pH range of 5-7.     

Kinetics of reduction of copper(II) by sodium tetrahydroborate

Summary The kinetics of reduction of copper(II) ion by sodium tetrahydroborate in buffered aqueous solution have been investigated. The rate of the reaction is first order in the concentrations of each of the reactants. The activation parameters were evaluated and a plausible mechanism for the reduction of copper(II) ion is proposed.     

Kinetics of reduction of transition metal ions by sodium tetrahydroborate. Reduction of molybdenum(VI) and tungsten(VI)

Summary The kinetics of reduction of molybdenum(VI) and tungsten(VI) ions by NaBH₄ in buffered aqueous solution have been investigated. The reaction rate depends upon the first powers of the concentrations of the reactants. The temperature was varied, and the activation parameters were evaluated. Chemical and spectral evidence for the formation of molybdenum(V) and tungsten(V), as the reaction products, is presented. Plausible mechanistic pathways for these reactions are suggested.     

Spectroscopic study of solid state photoreaction of di n-propyl ester of dicyano p-phenylenediacrylic acid

Photopolymerization reaction in di n-propyl ester of dicyano p-phenylene diacrylic acid crystal is shown to be mediated by exciton–phonon coupling. Raman phonon spectra suggest that at the initial stage of reaction progress, the reactant and the product form a solid solution. In the later stage, the reactant segregates out and forms its own lattice. The polymer lattice is shown to maintain a good degree of order. Infrared and Raman spectra confirm that the polymerization occurs by cyclobutane ring formation. © 1994 John Wiley & Sons, Inc.     

Concentration-dependent surface-enhanced Raman scattering of 2-benzoylpyridine adsorbed on colloidal silver particles

Surface-enhanced Raman scattering (SERS) of 2-benzoylpyridine (2-BP) adsorbed on silver hydrosols has been investigated. It has been observed that with a small change in the adsorbate concentration, the SER spectra of 2-BP show significant change in their features, indicating different orientational changes of the different part of the flexible molecule on the colloidal silver surface with adsorbate concentration. The time dependence of the SER spectra of the molecule has been explained in terms of aggregation of colloidal silver particles and co-adsorption and replacement kinetics of the adsorbed solute and solvent molecules on the silver surface. The broad long-wavelength band in the absorption spectra of the silver sol due to solute-induced coagulation of colloidal silver particles is found to be red-shifted with the increase in adsorbate concentration. The surface-enhanced Raman excitation profiles indicate that the resonance of the Raman excitation radiation with the new aggregation band contributes more to the SERS intensity than that with the original sol band.     

Synthesis and coating of silica supported Nickel Oxide particles over ceramic pre-forms through sol–gel derived layered double hydroxides

Silica supported Nickel Oxide fine particles have been synthesized through sol–gel derived Ni–Al Layered Double Hydroxide (LDH) and coated over honeycomb ceramic pre-forms through dip-coating technique. The powder products of supported materials have low crystallinity, negative zeta potential, exhibit high dispersibility and suitable for further processing by coating techniques. The powder X-ray diffraction (XRD) patterns have shown that there is an increase of basal spacing by 3.02 Å in acetylacetonate intercalated LDH. The particles of <2 μm size increase with the rise of LDH component in the composite. The particles of NiO structure formed on decomposition of composites have crystallite size <20 nm. Due to the interlayer reduction of NiO crystallites, the unsupported LDH on calcination gives Ni⁰ particles of size around 4.18 nm. The Scanning Electron Microscopy (SEM) patterns of coated supported suspensions over ceramic substrates show formation of thin, crack free coats with uniform distribution of particles.