Lipid composition of the silkworm Bombyx mori L

The constituents of silkworm fat were studied in detail. An unsaturated fat with a high concentration of phospholipid was generally observed. Its iodine value increased during metamorphosis. The free fatty acid concentration likewise increased from the spinning larvae to the moth stage. Analyses of silkworm organs revealed that the fat body had the most fat and the least free fatty acids, whereas haemolymph contained the least fat. Silk glands contained the maximum phospholipid percentage. Stearic acid predominated in those tissues that had a high percentage of phospholipid. Stearic acid was the predominant saturated fatty acid in both the phospholipids and lecithin, and it accounted for 35–50 per cent of the free fatty acids of all the tissues. Q10 was the ubiquinone present; also found were ubichromenol and tocopherol. Results show that silkworm sterol may be cholesterol. Intestines contained the maximum quantities of sterol, ubiquinone, ubichromenol, and tocopherol. The composition of silkworm phospholipids varies considerably from those of other insects, but lecithin is comparable in its composition with lecithins of other animals. The phospholipids had with them a highly complexed protein along with a polysaccharide. In experiments with snake venoms unsaturated fatty acids were found to be predominantly released from silkworm lecithin.

Nanostructured Copper(II) oxide thin film for alcohol sensing

Nanostructured copper(II) oxide film was deposited using reactive DC magnetron sputtering. It has been characterized using XRD, EDAX, XPS, and FESEM. The grain size of copper oxide film was found to be 40-65 nm with size distribution. The entire study was divided into two parts. In the first part, the film has been studied for its response to alcohol at different temperatures to find the optimum sensing temperature, whereas in the second part, the film sensitivity to different alcohol concentrations were studied at fixed optimum operating temperature. The optimum temperature for the response of ethanol was observed to be 400 C,and the response for different concentrations was found to be almost linear.

Reversible polyelectrolyte capsules as carriers for protein delivery

A reversible drug delivery system based on spontaneous deposition of a model protein into preformed microcapsules has been demonstrated for protein delivery applications. Layer-by-Layer assembly of poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) onto polystyrene sulfonate (PSS) doped CaCO3 particles, followed by core removal yielded intact hollow microcapsules having a unique property to induce spontaneous deposition of bovine serum albumin (BSA) at pH below its isoelectric point of 4.8, where it was positively charged. These capsules showed reversible pH dependent open and closed states to fluorescence labeled dextran (FITC-Dextran) and BSA (FITC-BSA). The loading capacity of BSA increased from 9.1 x 10(7) to 2.03 x 10(8) molecules per capsule with decrease in pH from 4.5 to 3.The loading of BSA-FITC was observed by confocal laser scanning microscopy (CLSM), which showed homogeneous distribution of protein inside the capsule. Efficient loading of BSA was further confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM).The interior capsule concentration was as high as 209 times the feeding concentration when the feeding concentration was increased from 1 to 10 mg/ml. The deposition was initially controlled by spontaneous loading mechanism at lower BSA concentration followed by diffusion controlled loading at higher concentration; which decreased the loading efficiency from 35% to 7%. Circular dichroism (CD) measurements and Fourier transform infrared spectroscopy (FTIR) confirmed that there was no significant change in conformation of released BSA in comparison with native BSA. The release was initially burst in the first 0.5 h and sustained up to 5 h. The hollow capsules were found to be biocompatible with mouse embryonic fibroblast (MEF) cells during in vitro cell culture studies. Thus these pH sensitive polyelectrolyte microcapsules may offer a promising delivery system for water soluble proteins and peptides. (C) 2010 Elsevier B.V. All rights reserved.

Magnetic properties of nanostructured ferrimagnetic zinc ferrite

Nanostructured ZnFe2O4 ferrites with different grain sizes were prepared by high energy ball milling for various milling times. Both the average grain size and the root mean square strain were estimated from the x-ray diffraction line broadening. The lattice parameter initially decreases slightly with milling and it increases with further milling. The magnetization is found to increase as the grain size decreases and its large value is attributed to the cation inversion associated with grain size reduction. The Fe-57 Mossbauer spectra were recorded at 300 K and 77 K for the samples with grain sizes of 22 and 11 nm. There is no evidence for the presence of the Fe2+ charge state. At 77 K the Mossbauer spectra consist of a magnetically ordered component along with a doublet due to the superparamagnetic behaviour of small crystalline grains with the superparamagnetic component decreasing with grain size reduction. At 4.2 K the sample with 11 nm grain size displays a magnetically blocked state as revealed by the Mossbauer spectrum. The Mossbauer spectrum of this sample recorded at 10 K in an external magnetic field of 6 T applied parallel to the direction of gamma rays clearly shows ferrimagnetic ordering of the sample. Also, the sample exhibits spin canting with a large canting angle, maybe due to a spin-glass-like surface layer or grain boundary anisotropies in the material.

Effect of phenoxy acids and their derivatives on lipid metabolism in groundnut (Arachis hypogaea) leaves

The effect of four phenoxy compounds [2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid, 4-chlorophenoxyacetic acid 2-(dimethylamino)ethyl ester (centrophenoxine), and 4-chlorophenoxy ethyl 2-(dimethylamino) ethyl ether (neophenoxine)] on lipid metabolism in groundnut (Arachis hypogaea) leaves was investigated under nonphotosynthetic conditions. In experiments with leaf disks, the uptake of [1-14C]acetate, [32P]orthophosphate, [35S]sulfate and [methyl-14C]choline was substantially inhibited by all the phenoxy compounds except neophenoxine. When the incorporation of these precursors into lipids was measured and expressed as percentage of total uptake, there was significant inhibition of incorporation of [1-14C]acetate and [32P]orthophosphate into lipids by all the compounds except neophenoxine. The incorporation of [methyl-14C]choline was unaffected by all except centrophenoxine which showed stastically significant stimulation. [35S]Sulfate incorporation into lipids was markedly inhibited only by centrophenoxine. The fatty acid synthetase of isolated chloroplasts assayed in the absence of light was inhibited 20–50% by the phenoxy compounds at 0.5 mM concentration. This inhibition showed a dependence on time of preincubation with the herbicide suggesting an interaction with the enzyme. It was, however, reversible and excess substrate did not prevent the inhibition, suggesting that the herbicide interaction may not be at the active site. sn-Glycerol-3-phosphate acyltransferase in the chloroplast and microsomal fractions was inhibited by 2,4-D while the phosphatidic acid phosphatase was insensitive to all the phenoxy compounds. It is concluded that phenoxy compounds affect precursor uptake, their incorporation into lipids, and the chloroplast fatty acid synthetase. The free acids were the most potent compounds while the ester (centrophenoxine) was less effective and the ether (neophenoxine) was completely ineffective in their influence on lipid metabolism.

Al/SiC carriers for microwave integrated circuits by a new technique of pressureless infiltration

Materials with high thermal conductivity and thermal expansion coefficient matching with that of Si or GaAs are being used for packaging high density microcircuits due to their ability of faster heat dissipation. Al/SiC is gaining wide acceptance as electronic packaging material due to the fact that its thermal expansion coefficient can be tailored to match with that of Si or GaAs by varying the Al:SiC ratio while maintaining the thermal conductivity more or less the same. In the present work, Al/SiC microwave integrated circuit (MIC) carriers have been fabricated by pressureless infiltration of Al-alloy into porous SiC preforms in air. This new technique provides a cheaper alternative to pressure infiltration or pressureless infiltration in nitrogen in producing Al/SiC composites for electronic packaging applications. Al-alloy/65vol% SiC composite exhibited a coefficient of thermal expansion of 7 x 10(-6) K-1 (25 degrees C-100 degrees C) and a thermal conductivity of 147 Wm(-1) K-1 at 30 degrees C. The hysteresis observed in thermal expansion coefficient of the composite in the temperature range 100 degrees C-400 degrees C has been attributed to the presence of thermal residual stresses in the composite. Thermal diffusivity of the composite measured over the temperature range from 30 degrees C to 400 degrees C showed a 55% decrease in thermal diffusivity with temperature. Such a large decrease in thermal diffusivity with temperature could be due to the presence of micropores, microcracks, and decohesion of the Al/SiC interfaces in the microstructure (all formed during cooling from the processing temperature). The carrier showed satisfactory performance after integrating it into a MIC.

On the admittance of lipid bilayer membranes: Part I. Membrane-permeable ions

The modular formalism of Rangarajan [J. Electroanal. Chem., 55 (1974) 297] has been applied to the admittance of lipid bilayer membranes. The method leads to equations which clearly show the interrelations between the various partial processes involved in ion transport, and which allow examination of model assumptions without the need for a complete rederivation of the membrane admittance. Explicit expressions are given for both the continuum and single jump models. The former includes the ionic displacement component, important mostly at high frequencies.

On the admittance of lipid bilayer membranes: Part I. Membrane-permeable ions

The modular formalism of Rangarajan [J. Electroanal. Chem., 55 (1974) 297] has been applied to the admittance of lipid bilayer membranes. The method leads to equations which clearly show the interrelations between the various partial processes involved in ion transport, and which allow examination of model assumptions without the need for a complete rederivation of the membrane admittance. Explicit expressions are given for both the continuum and single jump models. The former includes the ionic displacement component, important mostly at high frequencies.

Occurrence of Lipid Peroxidation in Brain Microsomes in the Presence of NADH and Vanadate

Oxidation of NADH by rat brain microsomes was stimulated severalfold on addition of vanadate. During the reaction, vanadate was reduced, oxygen was consumed, and H2O2 was generated with a stoichiometry of 1:1 for NADH/O2, as in the case of other membranes. Extra oxygen was found to be consumed over that needed for H2O2 generation specifically when brain microsomes were used. This appears to be due to the peroxidation of lipids known to be accompanied by a large consumption of oxygen. Occurrence of lipid peroxidation in brain microsomes in the presence of NADH and vanadate has been demonstrated. This activity was obtained specifically with the polymeric form of vanadate and with NADH, and was inhibited by the divalent cations Cu2+, Mn2+, and Ca2+, by dihydroxy-phenolic compounds, and by hemin in a concentration-dependent fashion. In the presence of a small concentration of vanadate, addition of an increasing concentration of Fe2+ gave increasing lipid peroxidation. After undergoing lipid peroxidation in the presence of NADH and vanadate, the binding of quinuclidinyl benzylate, a muscarinic antagonist, to brain membranes was decreased.

Microwave Assisted Synthesis of Nanostructured Titanium Dioxide with High Photocatalytic Activity

TiO2 (anatase) was synthesized using a microwave-irradiation-assisted chemical method. The reaction conditions were varied to obtain unique nanostructures of TiO2 comprising nanometric spheres giving the materials a very porous morphology. The oxide was characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The specific surface area and porosity were quantified by the BET method, and the degradation of dyes was carried out using these materials. The photocatalytic activity of the nanometric TiO2 was significantly higher than that of commercially available TiO2 (Degussa P25) for the degradation of the dyes.

Interaction of melittin with endotoxic lipid

Several amphipathic and cationic substances are known to bind lipid A, the toxic component of bacterial lipopolysaccharides. In this report, we have characterized, by fluorescence methods, the interaction of melittin, an amphipathic and basic 26-residue polypeptide isolated from bee venom, with lipid A. The stoichiometry of the complex appears to be two molecules of melittin to one of lipid A with a dissociation constant of 2.5 × 10 −6 M. The binding of melittin not only modifies the endotoxic properties of lipid A in a number of biological assays, but also results in abrogation of the hemolytic activity of melittin. A model of the complex is proposed based on the known structures of lipid A and melittin, and the observed stoichiometry of binding.

Nanomechanical properties of silicon surfaces nanostructured by excimer laser

Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses at a fixed laser fluence of 5 J cm(-2). A single-crystal silicon 311] surface was severely damaged by laser irradiation and became nanocrystalline with an enhanced porosity. The resulting laser-treated surface consisted of nanometer-sized particles. The pore size was controlled by adjusting the angle of incidence and the number of laser pulses, and varied from nanometers to microns. The extent of nanocrystallinity was large for the surfaces irradiated at a small angle of incidence and by a high number of pulses, as confirmed by x-ray diffraction and Raman spectroscopy. The angle of incidence had a stronger effect on the structure and nanomechanical properties than the number of laser pulses.

Precursor Dependent Microstructure Evolution and Nonstoichiometry in Nanostructured Cerium Oxide Coatings Using the Solution Precursor Plasma Spray Technique

A solution precursor plasma spray (SPPS) technique has been used for direct deposition of cerium oxide nanoparticles (CNPs) from various cerium salt solutions as precursors. Solution precursors were injected into the hot zone of a plasma plume to deposit CNP coatings. A numerical study of the droplet injection model has been employed for microstructure development during SPPS. The decomposition of each precursor to cerium oxide was analyzed by thermogravimetric-differential thermal analysis and validated by thermodynamic calculations. The presence of the cerium oxide phase in the coatings was confirmed by X-ray diffraction studies. Transmission electron microscopy studies confirmed nanocrystalline (grain size <14 nm) characteristic of the coatings. X-ray photoelectron spectroscopy studies indicated the presence of a high concentration of Ce3+ (up to 0.32) in the coating prepared by SPPS. The processing and microstructure evolution of cerium oxide coatings with high nonstoichiometry are reported.

Molecular modelling of saccharide-lipid interactions

Certain saccharides, including trehalose, sucrose and glucose, stabilize lipid bilayers against dehydration. It has been suggested that these saccharides replace waters of hydration as the system is dried, thereby maintaining the headgroups at their hydrated spacing. The lipid acyl chains consequently have sufficient free volume to remain in the liquid crystallines state, and the processes that disrupt membrane integrity are inhibited. Initial molecular graphic investigations of a model trehalose/DMPC system supported this idea (Chandrasekhar, I. and Gaber, B.P. (1988) J. Biomol. Stereodyn, 5, 1163–1171). We have extended these studies to glucose and sucrose. A set of AMBER potential parameters has been established that reproduce simple saccharide conformations, including the anomeric effect. Extensive energy minimizations have been conducted on all three systems. The saccharide-lipid interaction energies become less stable in the order trehalose lipid complexes becom eless negative in the order trehalose