Glycosyltransferases (GTs) catalyse the reaction of glyco‐conjugation of various biomolecules by transferring the saccharide moieties from an activated nucleotide sugar to nucleophilic glycosyl ...acceptor. In insects, GTs show diverse temporal and site‐specific expression patterns and thus play significant roles in forming the complex biomolecular structures that are necessary for insect survival, growth and development. Several insects exhibit GT‐mediated detoxification as a key defence strategy against plant allelochemicals and xenobiotic compounds, as well as a mechanism for pesticide cross‐resistance. Also, these enzymes act as crucial effectors and modulators in various developmental processes of insects such as eye development, UV shielding, cuticle formation, epithelial development and other specialized functions. Furthermore, many of the known insect GTs have been shown to play a fundamental role in other physiological processes like body pigmentation, cuticular tanning, chemosensation and stress response. This review provides a detailed overview of the multifaceted functionality of insect GTs and summarizes numerous case studies associated with it.
In the Bayer process of extraction of alumina from bauxite, the insoluble product generated after bauxite digestion with sodium hydroxide at elevated temperature and pressure is known as ‘red mud’ or ...‘bauxite residue’. This alumina refinery waste is highly alkaline in nature with a pH of 10.5–12.5 and is conventionally disposed of in mostly clay-lined land-based impoundments. The alkaline constituents in the red mud impose severe and alarming environmental problems, such as soil and air pollution. Keeping in view sustainable re-vegetation and residue management, neutralization/treatment of red mud using different techniques is the only alternative to make the bauxite residue environmentally benign. Hence, neutralization techniques, such as using mineral acids, acidic waste (pickling liquor waste), coal dust, superphosphate and gypsum as amenders, CO2, sintering with silicate material and seawater for treatment of red mud have been studied in detail. This paper is based upon and emphasizes the experimental work carried out for all the neutralization techniques along with a comprehensive review of each of the processes. The scope, applicability, limitations and feasibility of these processes have been compared exhaustively. Merits and demerits have been discussed using flow diagrams. All the techniques described are technically feasible, wherein findings obtained with seawater neutralization can be set as a benchmark for future work. Further studies should be focused on exploring the economical viability of these processes for better waste management and disposal of red mud.
Semi-interpenetrating polymer network (IPN) microspheres of natural polymers, viz., gelatin and sodium carboxymethyl cellulose (NaCMC) were prepared by using glutaraldehyde (GA) as a crosslinker. ...Ketorolac tromethamine (KT), an anti-inflammatory and analgesic agent, was successfully encapsulated into IPN microspheres. Various formulations were prepared by varying the ratio of gelatin and NaCMC, % drug loading, and amount of GA. Microspheres were characterized by Fourier transform infrared spectroscopy (FTIR) to understand the formation of IPN structure and to confirm the absence of chemical interactions between drug, polymer, and crosslinking agent. Scanning electron microscopy (SEM) was used to study the surface morphology of the microspheres. SEM showed that particles have slightly rough surfaces. Particle size as measured by using laser light scattering technique gave an average size ranging from 247 to 535
μm. Differential scanning calorimetry (DSC) and X-ray diffraction (X-RD) studies were performed to understand the crystalline nature of the drug after encapsulation into IPN microspheres. Drug encapsulation of up to 67% was achieved as measured by the UV method. Both equilibrium and dynamic swelling experiments were performed in water. Diffusion coefficients (
D) of water transport through the microspheres were determined using an empirical equation. Values of
D decrease with increasing crosslinking as well as increasing content of NaCMC in the matrix. In vitro release studies indicated a dependence of release rate on both the extent of crosslinking and the amount of NaCMC used to produce microspheres, but slow release was extended up to 10
h. Cumulative release data were fitted to an empirical equation to compute diffusional exponent (
n), which indicated the non-Fickian trend for drug release.
Considerable research efforts have been directed towards developing safe and efficient chitosan-based particulate drug delivery systems. The present review outlines the major new findings on the ...pharmaceutical applications of chitosan-based micro/nanoparticulate drug delivery systems published over the past decade. Methods of their preparation, drug loading, release characteristics, and applications are covered. Chemically modified chitosan or its derivatives used in drug delivery research are discussed critically to evaluate the usefulness of these systems in delivering the bioactive molecules. From a literature survey, it is realized that research activities on chitosan micro/nanoparticulate systems containing various drugs for different therapeutic applications have increased at the rapid rate. Hence, the present review is timely.
Water ice exists on many objects in space. The most abundant icy species, among them water, are present in the icy satellites of the outer Solar System giant planets. The nuclei of comets, which are ...mainly composed of water ice, give another example of its abundance. In the interstellar medium (ISM), ice mantles, formed by molecular species sticking on dust grains, consist mainly of water ice. All these objects are exposed to ionizing radiation like ions, UV photons, and electrons. Sputtering of atoms, molecules, ions, and radicals from icy surfaces may populate and maintain exospheres of icy objects in the Solar System. In other respects, ionized hydrides such as OH+, H2O+, and H3O+ have been detected in the gas phase in star-forming regions. Interactions with cosmic rays could be an additional explanation to the current models for the formation of those species. In fact, laboratory simulations showed that the main components of the sputtered ionic species from water ice are oxygen hydrides. In this work, water ice targets were irradiated at several temperatures (10–200 K) by 90 keV O6+ ions, yielding an electronic stopping power of about 12 eV/Å, when the nuclear stopping power is comparable to the electronic stopping power. Sputtering of secondary ions after bombardment of the ice target was analyzed by time-of-flight mass spectrometry (TOF-SIMS). Besides hydrogen ions (H+, H2 +, H3 +), also O+, O2+, OH+, (H2O)+, and clusters of (H2O) n H+ with n = 1–8 are emitted. Our results show a progressive yield decrease with increasing temperature of all of the detected species. This is related to the structure of the ice: the ionic sputtering yield for crystalline ice is much lower than for an amorphous ice. For instance, amorphous ice at 10 K exhibits a yield of the order of 2 × 10–6 secondary (H2O) n H+ hydride ions/projectile (with n = 1–8). As the temperature is increasing toward the phase transition to crystalline ice, the yields decrease by about one order of magnitude.
Fragmentation of molecular nitrogen dimers (N_{2})_{2} induced by collision with low energy 90 keV Ar^{9+} ions is studied to evidence the influence of a molecular environment on the fragmentation ...dynamics of N_{2} cations. Following the capture of three or four electrons from the dimer, the three-body N_{2}^{+}+N^{m+}+N^{n+} with (m,n)=(1,1) or (1, 2) fragmentation channels provide clean experimental cases where molecular fragmentation may occur in the presence of a neighbor molecular cation. The effect of the environment on the fragmentation dynamics within the dimer is investigated through the comparison of the kinetic energy release (KER) spectra for these three-body channels and for isolated N_{2}^{(m+n)+} monomer cations. The corresponding KER spectra exhibit energy shifts of the order of 10 eV, attributed to the deformation of the N^{m+}+N^{n+} potential energy curves in the presence of the neighboring N_{2}^{+} cation. The KER structures remain unchanged, indicating that the primary collision process is not significantly affected by the presence of a neighbor molecule.
A simple and commercially viable method of preparation of chitosan microparticles (MPs) was adopted for the entrapment of clozapine, which can be easily scaled-up to controlled drug delivery dosage ...form. This method is devoid of tedious processes like emulsification in oil phase, spray-drying, etc. MPs have been prepared by changing the experimental variables such as extent of crosslinking and amount of clozapine loading in order to optimize the process variables on the final percent drug entrapment efficiency, size of MPs and release rates. Absence of chemical interactions between drug, polymer and crosslinking agent after the production of MPs was confirmed by Fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) spectra were obtained for clozapine-loaded chitosan MPs to understand the crystalline nature of the drug after entrapment. The results indicated a molecular level dispersion of clozapine in the polymer matrix.
Effect of crosslinking and drug loading on thermal decomposition of chitosan was studied by thermogravimetry (TGA) and these data indicated that pure chitosan is stable when compared to clozapine-loaded chitosan. MPs produced were irregular in shape, with average particle sizes in the range of 543–698 μm as measured by the laser light scattering technique. Clozapine entrapment up to 98.97% was obtained as determined by high performance liquid chromatography. In vitro release studies were performed in phosphate buffer pH 7.4 solution and the release of clozapine was achieved up to 12 h. Swelling studies were conducted in water and diffusion coefficients (
D) and diffusional exponents (
n) for water transport were determined using the empirical equation. In vivo absorption kinetics of clozapine and clozapine-loaded MPs were investigated in albino rats. These results indicated that absorption of clozapine from MPs was delayed since the area under the curve was higher when compared to neat clozapine.
ABSTRACT
The processing of H2O:CO2:CH4 (10:1:1) and H2O:CO2:CH4:NH3 (10:1:1:1) ices at 72 K by oxygen ions was studied in an attempt to simulate the physicochemical effects induced by energetic ions ...on the surface of Enceladus (or similar cold surfaces in the outer Solar System). The experiments were carried out at the Grand Accélérateur National d’Ions Lourds (GANIL) in Caen/France. The samples were irradiated with 15.7-MeV O5+ at the IRRadiation SUD (IRRSUD) beamline and with 108-keV O6+ at the Accélérateurs pour les Recherches avec les Ions de Basses Energies (ARIBE) beamline. The frozen samples were monitored by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy (4000–650 cm−1, 2.5–15.4 μm, at 1 cm−1 resolution). The identified molecular species formed during irradiation were CO, OCN−, CH3OH, HCN, CN−, H2CO3, HNCO, HCO and CO3. The effective formation cross-sections for the synthesis of new species and the effective molecular destruction cross-sections of the parent species in the experiments with MeV ions were found to be of the order of 10−14–10−13 cm2. For the keV ion experiments, these values were of the order of 10−16–10−15 cm2. The fluence at which the sample reaches chemical equilibrium and the molecular abundances in this region (equilibrium branching ratios) were estimated. These experiments suggest that the chemical inventory on the surface of Enceladus can be influenced by the incidence of charged particles on to the moon’s surface.
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