Purification and characterization of an extracellular β-glucosidase from the thermophilic fungus Sporotrichum thermophile and its influence on cellulase activity

Multiple forms of beta-glucosidase (EC 3.2.1.21) of Sporotrichum thermophile were produced when the fungus was grown in a cellulose medium. One beta-glucosidase was purified 16-fold from 6-d-old culture filtrates by ion-exchange and gel-filtration chromatography. The purified enzyme was free of cellulase activity. It hydrolysed aryl beta-D-glucosides and beta-D-linked diglucosides. It was optimally active at pH 5.4, at 65-degrees-C. The apparent K(m) values for p-nitrophenyl beta-D-glucoside (PNPG) and cellobiose were 0.29 and 0.83 mm, respectively. Glucose, fucose, nojirimycin and gluconolactone inhibited beta-glucosidase competitively. At high (> 1 mm) substrate concentration, beta-glucosidase catalysed a parallel transglycosylation reaction. The transglycosylation product formed from cellobiose appeared to be a beta-linked tetramer of glucose. Admixtures of beta-glucosidase and cellulase components showed that the concept of cellobiose inhibition of cellulases was not valid for all components of the cellulase system of S. thermophile. Beta-Glucosidase supplementation also stimulated cellulose hydrolysis by cellulases when there was no accumulation of cellobiose in reaction mixture.

Purification and Partial Characterization of Microsomal NADH-Cytochrome b5 Reductase from Higher Plant Catharanthus roseus

A simple three step procedure was used to purify microsomal NADH-cytochrome b5 (ferricyanide) reductase to homogeneity from the higher plant C. roseus. The microsomal bound reductase was solubilized using zwitterionic detergent-CHAPS. The solubilized reductase was subjected to affinity chromatography on octylamino Sepharose 4B, blue 2-Sepharose CL-6B and NAD+-Agarose. The homogeneous enzyme has an apparent molecular weight of 33,000 as estimated by SDS-PAGE. The purified enzyme catalyzes the reduction of purified cytochrome b5 from C. roseus in the presence of NADH. The reductase also readily transfers electrons from NADH to ferricyanide (Km 56 μM), 2,6-dichlorophenolindophenol (Km 65 μM) and cytochrome Image via cytochrome b5 but not to menadione.

Serotypic and genotypic characterization of human serotype 10 rotaviruses from asymptomatic neonates

Human rotaviruses were isolated from asymptomatic neonates at various hospitals and clinics in the city of Bangalore, India, and were found to be subgroup I specific and possess long RNA patterns (M. Sukumaran, K. Gowda, P. P. Maiya, T. P. Srinivas, M. S. Kumar, S. Aijaz, R. R. Reddy, L. Padilla, H. B. Greenberg, and C. D. Rao, Arch. Virol. 126:239-251, 1992). Three of these strains were adapted to tissue culture and found by serotype analysis and neutralization assays to be of serotype 10, a serotype commonly found in cattle but infrequently found in humans and not previously identified in neonates. By RNA-RNA hybridization, a high level of relatedness to a serotype 10 bovine rotavirus strain and a low-to-medium level of relatedness to a human rotavirus strain were observed. Since this human isolate shares a genogroup with bovine rotavirus, it is likely that it originated by interspecies transmission. A human rotavirus strain isolated from asymptomatic neonates and similar to bovine rotavirus might represent a good vaccine candidate.

Synthesis and characterization of single-crystalline alpha-MoO3 nanofibers for enhanced Li-ion intercalation applications

High quality, single-crystalline alpha-MoO3 nanofibers are synthesized by rapid hydrothermal method using a polymeric nitrosyl-complex of molybdenum(II) as molybdenum source without employing catalysts, surfactants, or templates. The possible reaction pathway is decomposition and oxidation of the complex to the polymolybdate and then surface condensation on the energetically favorable 001] direction in the initially formed nuclei of solid alpha-MoO3 under hydrothermal conditions. Highly crystalline alpha-MoO3 nanofibers have grown along 001] with lengths up to several micrometres and widths ranging between 280 and 320 nm. The alpha-MoO3 nanofibers exhibit desirable electrochemical properties such as high capacity reversibility as a cathode material of a Li-ion battery.

Studies on the metabolism of a monoterpene ketone, R-(+)-pulegone-a hepatotoxin in rat: isolation and characterization of new metabolites

1. The metabolic disposition of R-(+)-pulegone (1) was examined in rats following four daily oral doses (250 mg/kg). 2. Six metabolites, namely pulegol (II), 2-hydroxy-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanone (III), 3,6-dimethyl-7a-hydroxy-5,6,7,7a-tetrahydro-2(4H)-benzofuranone (IV), menthofuran (V), 5-methyl-2-(1-methyl-1-carboxyethylidene)cyclohexanone (VI), and 5-methyl-5-hydroxy-2-(1-hydroxy-1-carboxyethyl)cyclohexanone (VII) have previously been isolated from rat urine, and identified (Moorthy et al. (1989a). Eight new metabolites have now been isolated from rat urine, namely, 5-hydroxy-pulegone (VIII), piperitone (IX), piperitenone (X), 7-hydroxy-piperitone (XI), 8-hydroxy piperitone (XII), p-cresol (XIII), geranic acid (XIV) and neronic acid (XV). These were identified by n.m.r., i.r. and mass spectrometry. 3. Based on these results, metabolic pathways for the biotransformation of R-(+)-pulegone in rat have been proposed.

Synthesis, characterization, and thermal degradation studies on group VIA derived weak-link polymers

Polymers containing group VIA derived weak links, viz. poly(styrene disulfide) (PSD), poly- (styrene tetrasulfide) (PST), and poly(styrene diselenide) (PSDSE), have been synthesized. The polymers PSD and PST were characterized by NMR, IR, UV, TGA, and fast atom bombardment m w spectrometric (FABMS) techniques. The presence of different configurational sequences in PSD and PST were identified by *3C NMR spectroscopy. PSDSE, being insoluble in common organic solvents, was characterized using solid-state lac NMR (CP-MAS) spectroscopy. Thermal degradation of polymers under direct pyrolysis-mass spectrometric (DP-MS) conditions revealed that all the polymers undergo degradation through the weaklink scission. A comparative study of the pyrolysis products of these polymers with that of poly(styrene peroxide) (PSP) revealed a smooth transformation down the group with no monomer (styrene or oxygen) formation in PSP to only styrene and selenium metal in PSDSE. This trend of group VIA is explained from the energetics of the C-X bond (X = 0, S, and Se) which also seems to be important in addition to the weak X-X bond cleavage. In PSP and PSD, the behavior is also explained from the energetics of the alkoxy and thiyl radicals. The unique exothermic degradation in PSP compared to endothermic degradation in PSD and PSDSE is explained from the nature of the producta of degradation.

Synthesis of Layered Perovskite Oxides, ACa2-xLaxNb3-xTix010 (A = K, Rb, Cs), and Characterization of New Solid Acids, HCa2-xLaxNb3-xTixOlo (0 < x d 2), Exhibiting Variable Bronsted Acidity?

Layered perovskite oxides of the formula ACa~,La,Nb3-,Ti,010 (A = K, Rb, Cs and 0 < x d 2) have been prepared. The members adopt the structures of the parent ACazNb3010. Interlayer alkali cations in the niobium-titanium oxide series can be ion-exchanged with Li+, Na+, NH4+, or H+ to give new derivatives. Intercalation of the protonated derivatives with organic bases reveals that the Bronsted acidity of the solid solution series, HC~ ~ , L ~ ,N~ ~ , T ~ ,dOep~eOnd, s on the titanium content. While the x = 1 member (HCaLaNbzTiOlo) is nearly as acidic as the parent HCazNb3010, the x = 2 member (HLazNbTizOlo) is a weak acid hardly intercalating organic bases with pKa - 11.3. The variation of acidity is probably due to an ordering of Nb/Ti atoms in the triple octahedral perovskite slabs, [Ca~,La,Nb~,Ti,0~0], such that protons are attached to NbO6 octahedra in the x = 1 member and to Ti06 octahedra in the x = 2 member.

Synthesis, characterization and photoluminescence properties of CaSiO3: Eu3+ red phosphor

CaSiO3:Eu3+ (1-5 mol%) red emitting phosphors have been synthesized by a low-temperature solution combustion method. The phosphors have been well characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical spectroscopy. PXRD patterns reveal monoclinic CaSiO3 phase can be obtained at 900 degrees C. The SEM micrographs show the crystallites with irregular shape, mostly angular. Upon 254 nm excitation, the phosphor show characteristic fluorescence D-5(0) -> F-7(J) (J = 0, 1, 2, 3, 4) of the Eu3+ ions. The electronic transition located at 614 nm corresponding to D-5(0) -> F-7(2) of Eu3+ ions, which is stronger than the magnetic dipole transition located at 593 nm corresponding to D-5(0) -> F-7(1) of Eu3+ ions. Different pathways involved in emission process have been studied. Concentration quenching has been observed for Eu3+ concentration >4 mol%. UV-visible absorption shows an intense band at 240 nm in undoped and 270 nm in Eu3+ doped CaSiO3 which is attributed to oxygen to silicon (O-Si) ligand-to-metal charge-transfer (LMCT) band in the SiO32- group. The optical energy band gap is widened with increase of Eu3+ ion dopant. (C) 2010 Elsevier B.V. All rights reserved.

Crystal structure and electrical properties of CaNaBi2Nb3O12 ceramics

Monophasic CaNaBi2Nb3O12 powders were synthesized via the conventional solid-state reaction route. Rietveld refinement of the X-ray powder diffraction (XRD) data and selected area electron diffraction (SAED) studies confirmed the phase to be a three-layer Aurivillius oxide associated with an orthorhombic B2cb space group. The dielectric properties of the ceramics have been studied in the 300-800 K temperature range at various frequencies (1 kHz to 1 MHz). A dielectric anomaly was observed at 676 K for all the frequencies corresponding to the ferroelectric to paraelectric phase transition as it was also corroborated by the high temperature X-ray diffraction studies. The incidence of the polarization-electric field (P vs. E) hysteresis loop demonstrated CaNaBi2Nb3O12 to be ferroelectric.

Growth of alkali metal periodates from silica gel and their characterization

Single crystals (up to 1 cm size) of K, Rb and Cs periodates have been grown in silica gel. In general, good quality crystals were obtained in gel of specific gravity 1.04 and pH 4. The metal/iodine ratios were determined and compared with calculated values. Morphological studies were carried out using a bicircle optical goniometer. Other characterization methods include X-ray diffraction, optical absorption, differential scanning calorimetry and optical microscopy. Microscopic examination of CsIO4 crystals in particular has revealed the existence of ferroelastic domains in the crystal. The structural basis for the occurence of ferroelasticity in this crystal is discussed and the high temperature space group is predicted.

Synthesis, characterization and antioxidant activity of angiotensin converting enzyme inhibitors

Angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I (Ang I) to angiotensin II (Ang II). ACE also cleaves the terminal dipeptide of vasodilating hormone bradykinin (a nonapeptide) to inactivate this hormone. Therefore, inhibition of ACE is generally used as one of the methods for the treatment of hypertension. `Oxidative stress' is another disease state caused by an imbalance in the production of oxidants and antioxidants. A number of studies suggest that hypertension and oxidative stress are interdependent. Therefore, ACE inhibitors having antioxidant property are considered beneficial for the treatment of hypertension. As selenium compounds are known to exhibit better antioxidant behavior than their sulfur analogues, we have synthesized a number of selenium analogues of captopril, an ACE inhibitor used as an antihypertensive drug. The selenium analogues of captopril not only inhibit ACE activity but also effectively scavenge peroxynitrite, a strong oxidant found in vivo.

Development and characterization of monoclonal antibodies against WbSXP-1 for the detection of circulating filarial antigens

The importance of developing effective assays to diagnose, monitor and evaluate human lymphatic filariasis has been emphasized by the World Health Organization. Presently, few immunodiagnostics are available for filarial monitoring programmes. The Wuchereria bancrofti (Wb) SXP-1 parasite protein, with 84% homology to Brugia malayi (Bm) SXP-1, was found to be highly immunogenic. WbSXP-1 is one among the diagnostic candidate molecules that were used for developing a rapid-antibody-flow-through diagnostic kit for filariasis. Studies were initiated with the aim of developing monoclonal antibodies against recombinant WbSXP-1 and prospective applications for the detection of both circulating Wb and Bm antigens in serum samples from infected individuals. The monoclones 1A6C2 of subclass IgG1k, and 2A12F8 of class IgM, specifically detected Wb and Bm microfilaria isolated from patients and did not show cross-reactivity with other filarial recombinant antigens. We anticipate that this work will address the problems faced in the rapid diagnosis of human lymphatic filariasis in endemic areas in developing countries.

Self-assembly of neutral and cationic Pd-II organometallic molecular rectangles: synthesis, characterization and nitroaromatic sensing

Design and synthesis of three novel 2 + 2] self-assembled molecular rectangles 1-3 via coordination driven self-assembly of predesigned Pd(II) ligands is reported. 1,8-Diethynylanthracene was assembled with trans-Pd(PEt3)(2)Cl-2 in the presence of CuCl catalyst to yield a neutral rectangle 1 via Pd-C bond formation. Complex 1 represents the first example of a neutral molecular rectangle obtained via C-Pd coordination driven self-assembly. A new Pd-2(II) organometallic building block with 180 degrees bite-angle 1,4-bistrans-(ethynyl)Pd(PEt3)(2)(NO3)] benzene (M-2) containing ethynyl functionality was synthesized in reasonable yield by employing Sonagashira coupling reaction. Self-assembly of M-2 with two organic clip-type donors (L-2-L-3) afforded 2 + 2] self-assembled molecular rectangles 2 and 3, respectively L-2 = 1,8-bis(4-pyridylethynyl) anthracene; L-3 = 1,3-bis(3-pyridyl) isophthalamide]. The macrocycles 1-3 were fully characterized by multinuclear NMR and ESI-MS spectroscopic techniques, and in case of 1 the structure was unambiguously determined by single crystal X-ray diffraction analysis. Incorporation of Pd-ethynyl bonds helped to make the assemblies p-electron rich and fluorescent in nature. Complexes 1-2 showed quenching of fluorescence intensity in solution in presence of nitroaromatics, which are the chemical signatures of many commercially available explosives.

Preparation and Characterization of MWCNT/ZnO nanoparticles Hybrid

ZnO nanoparticles (ZnO NPs) were grown on the surface of multiwall carbon nanotubes (MWCNTs) by a wet chemical synthesis route. The anchoring of ZnO NPs on acid-treated MWCNTs was achieved under remarkably mild reaction conditions (low temperature, atmospheric pressure, without any capping agents and no need for subsequent thermal annealing). MWCNT/ZnO NPs hybrid samples with varying loading of ZnO NPs are prepared. A very high degree of dispersion of ZnO NPs over the surface of MWCNT was achieved by suitably controlling the ratio of ZnO NPs and MWCNTs in the solution. The hybrid sample was characterized by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy (XPS). Transmission electron microscope images of the as-prepared MWCNT/ZnO NPs hybrid reveal that mono-dispersed ZnO NPs are anchored stably on functionalized MWCNTs. The interaction of ZnO NPs with MWCNT surface was interpreted through XPS analysis.

Creep in TiO2 doped Zirconia: Implications for high strain rate superplasticity

In ceramics, dopants offer the possibility of higher creep rates by enhancing diffusion. The present study examines the potential for high strain rate superplasticity in a TiO2 doped zirconia, by conducting creep experiments together with microstructural characterization. It is shown that both pure and doped zirconia exhibit transitions in creep behaviour from Coble diffusion creep with n similar to 1 to an interface controlled process with n similar to 2. Doping with TiO2 enhances the creep rate by over an order of magnitude. There is evidence of substantial grain boundary sliding, consistent with diffusion creep.