Purification and properties of an inhibitor for nicotinamide-adenine dinucleotidase from Mycobacterium tuberculosis H37Rv

The excess of free inhibitor for the enzyme NADase present in the crude cell-free extracts of Mycobacterium tuberculosis H37Rv has been purified by chromatography on a DEAE-cellulose column and adsorption and elution from alumina Cγ-gel. Some of the properties of the purified inhibitor have been studied and attempts have been made to elucidate the nature of combination between the enzyme and the inhibitor. The purified inhibitor may be glycoprotein in nature, and considerable loss in the activity of the inhibitor preparations could be brought about by trypsin digestion. The inhibitor was specific for the enzymes from M. tuberculosis H37Rv or H37Ra and could be stored for at least 6 months in the frozen state below 0 ° without any significant loss in activity. The inhibition was noncompetitive with respect to the substrates, and the enzyme-inhibitor complex formed was undissociable.

Effect of some organic acids on leaf phosphatase from French beans

1. The common organic acids inhibited leaf phosphatase activity, This effect is mostly due to the hydroxyl groups in them. 2. The less common organic acids, which have only carboxyl groups, did not show any marked inhibitory action on phosphatase activity. 3. The less common organic acids eluted the leaf phosphatase after adsorption on aluminacγ gel to a greater extent than the more common organic acids. 4. The second elution of the purified enzyme from the aluminacγ gel was not possible with the organic acids as it was adsorbed on the gel.

Detection of a periodic structure hidden in random background: the role of signal amplitude in the matched filter detection method

The matched filter method for detecting a periodic structure on a surface hidden behind randomness is known to detect up to (r(0)/Lambda) gt;= 0.11, where r(0) is the coherence length of light on scattering from the rough part and 3 is the wavelength of the periodic part of the surface-the above limit being much lower than what is allowed by conventional detection methods. The primary goal of this technique is the detection and characterization of the periodic structure hidden behind randomness without the use of any complicated experimental or computational procedures. This paper examines this detection procedure for various values of the amplitude a of the periodic part beginning from a = 0 to small finite values of a. We thus address the importance of the following quantities: `(a)lambda) `, which scales the amplitude of the periodic part with the wavelength of light, and (r(0))Lambda),in determining the detectability of the intensity peaks.

A study of the purification and properties of tryptophan synthetase of Bengal gram (Cicer arietinum)

Active preparations of tryptophan synthetase were obtained from Bengal gram (Cicer arietinum) by the following procedure: (1) precipitation of inactive materials by manganous sulfate, (2) Adsorption of impurities on Alumina Cγ, (3) Adsorption of tryptophan synthetase on tricalcium phosphate gel, removal of inert protein from the gel by treatment with phosphate buffer (pH 7.2), and selective elution of the enzyme by 0.15 M phosphate buffer pH 7.2 containing 10% ammonium sulfate and 10−3 M serine. A 220-fold purification of the enzyme with 44% recovery of the activity was achieved. The pH optimum, effect of temperature, and substrate concentration and other properties of the purified enzyme have been studied in detail. Only the Image -isomer of serine takes part in the reaction. The Km values for indole, Image -serine, and Image -serine were calculated to be 0.66, 4.1, and 8.6 × 10−4 M, respectively. A kinetic study of the inhibition of tryptophan synthetase by indole-propionic acid has shown that it is of a competitive type. It has been demonstrated for the first time that 4-nitro-salicylaldehyde can replace pyridoxal phosphate as a coenzyme for the tryptophan synthetase reaction.

A colorimetric method for determination of pyrocatechol and related substances

A colorimetric assay for the quantitative determination of catecholic compounds was developed. The method was based on the observation that a red color was formed when nitrite was added to a solution containing pyrocatechol and sodium tungstate. Aromatic amines interfere with the reaction but this could be overcome by the addition of formaldehyde. When interfering substances are present along with pyrocatechol, it can be readily separated by paper chromatography and estimated after elution from the filter paper.

Action of N-bromosuccinimide on human hemoglobin and its possible bearing on heme-globin linkage

A reaction of N-bromosuccinimide with the heme groups of hemoglobin has been studied spectrophotometrically. The reaction brings about the disappearance of characteristic absorption peaks of hemoglobin and is accompanied by the release of inorganic iron from the heme groups. Urea is obligatory for the reaction to take place at pH 4.0, while it can occur in the absence of urea at pH 7.0. The spectrum of hemoglobin which does not show any peak in the Soret region at pH 4.0 is “normalized” in the presence of urea or sucrose at the same pH. The effect of “normalization” in 8 M urea is apparent over the pH range 3.0–4.5. From the obligatory requirement of urea and sucrose for “normalization” of spectrum and the dependence of the release of inorganic iron on the concentration of urea, it is suggested that heme groups are “buried” within the globin at pH 4.0 and not dissociated from globin as supposed before.

Ultrasonic studies in chemically active liquid media (1) aqueous solution of N2O4

Using a pulse method the ultrasonic absorption has been studied in the frequency range of 2 to 10 Mc/s in dilute aqueous solutions of nitrogen tetroxide gas at room temperature. The absorption peaks (αλ vs frequency) observed in this study are attributed to the ionic dissociation reaction of the nitrous acid into its constituent ions. The rate constants of the forward and backward reactions are calculated using the theory of Tabuchi. The variation of the logarithm of the rate constant of the bimolecular ionic reaction, namely, log10 kb, with the square root of ionic strength qualitatively follows Brönsted's theory for ionic reactions in solutions.

Oxidation of catechol in plants : III. Purification and properties of the diphenylene dioxide 2,3-quinone-forming enzyme system from Tecoma leaves

In attempting to determine the nature of the enzyme system mediating the conversion of catechol to diphenylenedioxide 2,3-quinone, in Tecoma leaves, further purification of the enzyme was undertaken. The crude enzyme from Tecoma leaves was processed further by protamine sulfate precipitation, positive adsorption on tricalcium phosphate gel, and elution and chromatography on DEAE-Sephadex. This procedure yielded a 120-fold purified enzyme which stoichiometrically converted catechol to diphenylenedioxide 2,3-quinone. The purity of the enzyme system was assessed by polyacrylamide gel electrophoresis. The approximate molecular weight of the enzyme was assessed as 200,000 by gel filtration on Sephadex G-150. The enzyme functioned optimally at pH 7.1 and at 35 °C. The Km for catechol was determined as 4 × 10−4 Image . The enzyme did not oxidize o-dihydric phenols other than catechol and it did not exhibit any activity toward monohydric and trihydric phenols and flavonoids. Copper-chelating agents did not inhibit the enzyme activity. Copper could not be detected in the purified enzyme preparations. The purified enzyme was not affected by extensive dialysis against copper-complexing agents. It did not show any peroxidase activity and it was not inhibited by catalase. Hydrogen peroxide formation could not be detected during the catalytic reaction. The enzymatic conversion of catechol to diphenylenedioxide 2,3-quinone by the purified Tecoma leaf enzyme was suppressed by such reducing agents as GSH and cysteamine. The purified enzyme was not sensitive to carbon monoxide. It was not inhibited by thiol inhibitors. The Tecoma leaf was found to be localized in the soluble fraction of the cell. Treatment of the purified enzyme with acid, alkali, and urea led to the progressive denaturation of the enzyme.

Nonlinear vibration analysis of composite laminated and sandwich plates with random material properties

Nonlinear vibration analysis is performed using a C-0 assumed strain interpolated finite element plate model based on Reddy's third order theory. An earlier model is modified to include the effect of transverse shear variation along the plate thickness and Von-Karman nonlinear strain terms. Monte Carlo Simulation with Latin Hypercube Sampling technique is used to obtain the variance of linear and nonlinear natural frequencies of the plate due to randomness in its material properties. Numerical results are obtained for composite plates with different aspect ratio, stacking sequence and oscillation amplitude ratio. The numerical results are validated with the available literature. It is found that the nonlinear frequencies show increasing non-Gaussian probability density function with increasing amplitude of vibration and show dual peaks at high amplitude ratios. This chaotic nature of the dispersion of nonlinear eigenvalues is also r

Expression of GC-C, a receptor-guanylate cyclase, and its endogenous ligands uroguanylin and guanylin along the rostrocaudal axis of the intestine

Members of the receptor-guanylate cyclase (rGC) family possess an intracellular catalytic domain that is regulated by an extracellular receptor domain. GC-C, an intestinally expressed rGC, was initially cloned by homology as an orphan receptor. The search for its Ligands has yielded three candidates: STa (a bacterial toxin that causes traveler's diarrhea) and the endogenous peptides uroguanylin and guanylin. Here, by performing Northern and Western blots, and by measuring [I-125]STa binding and STa-dependent elevation of cGMP levels, we investigate whether the distribution of GC-C matches that of its endogenous ligands in the rat intestine. We establish that 1) uroguanylin is essentially restricted to small bowel; 2) guanylin is very low in proximal small bowel, increasing to prominent levels in distal small bowel and throughout colon; 3) GC-C messenger RNA and STa-binding sites are uniformly expressed throughout the intestine; and 4) GC-C-mediated cGMP synthesis peaks at the proximal and distal extremes of the intestine (duodenum and colon), but is nearly absent in the middle (ileum). These observations suggest that GC-C's activity may be posttranslationally regulated, demonstrate that the distribution of GC-C is appropriate to mediate the actions of both uroguanylin and guanylin, and help to refine current hypotheses about the physiological role(s) of these peptides.

Magnetotransport of Dirac fermions on the surface of a topological insulator

We study the properties of Dirac fermions on the surface of a topological insulator in the presence of crossed electric and magnetic fields. We provide an exact solution to this problem and demonstrate that, in contrast to their counterparts in graphene, these Dirac fermions allow relative tuning of the orbital and Zeeman effects of an applied magnetic field by a crossed electric field along the surface. We also elaborate and extend our earlier results on normal-metal-magnetic film-normal metal (NMN) and normal-metal-barrier-magnetic film (NBM) junctions of topological insulators [S. Mondal, D. Sen, K. Sengupta, and R. Shankar, Phys. Rev. Lett. 104, 046403 (2010)]. For NMN junctions, we show that for Dirac fermions with Fermi velocity vF, the transport can be controlled using the exchange field J of a ferromagnetic film over a region of width d. The conductance of such a junction changes from oscillatory to a monotonically decreasing function of d beyond a critical J which leads to the possible realization of magnetic switches using these junctions. For NBM junctions with a potential barrier of width d and potential V-0, we find that beyond a critical J, the criteria of conductance maxima changes from chi=eV(0)d/h upsilon(F)=n pi to chi=(n+1/2)pi for integer n. Finally, we compute the subgap tunneling conductance of a normal-metal-magnetic film-superconductor junctions on the surface of a topological insulator and show that the position of the peaks of the zero-bias tunneling conductance can be tuned using the magnetization of the ferromagnetic film. We point out that these phenomena have no analogs in either conventional two-dimensional materials or Dirac electrons in graphene and suggest experiments to test our theory.

Synthesis,characterization and photoluminescence properties of CaSiO3 :Dy3+ nanophosphors

CaSiO3 : Dy3+ (1-5 mol. %) nanophosphors were synthesized by a simple low-temperature solution combustion method. Powder X-ray diffraction patterns revealed that the phosphors are crystalline and can be indexed to a monoclinic phase. Scanning electron micrographs exhibited faceted plates and angular crystals of different sizes with a porous nature. Photoluminescence properties of the Dy3+-doped CaSiO3 phosphors were observed and analyzed. Emission peaks at 483, 573 and 610 nm corresponding to Dy3+ were assigned as F-4(9/2)-> H-6(15/2), F-4(9/2) -> H-6(13/2) and F-4(9/2) -> H-6(11/2) transitions, respectively, and dominated by the Dy3+ F-4(9/2) -> H-6(13/2) hyperfine transition. Experimental results revealed that the luminescence intensity was affected by both heat treatment and the concentration of Dy3+ (1-5 mol. %) in the CaSiO3 host. Optimal luminescence conditions were achieved when the concentration of Dy3+ was 2 mol. %. UV-visible absorption features an intense band at 240 nm, which corresponds to an O-Si ligand-to-metal charge transfer band in the SiO32- group. The optical energy band gap for the undoped sample was found to be 5.45 eV, whereas in Dy3+-doped phosphors it varies in the range 5.49-5.65 eV. The optical energy gap widens with increase of Dy3+ ion dopant.

Isolation Of A Cytokinin-Binding Protein From Cucumis-Sativus Cotyledons

A cytokinin-binding protein which exists as monomer and dimer was isolated from cucumber (Cucumis sativus L. var Guntur) cotyledons by affinity chromatography on AH-Sepharose-pi6 Ap /s> column. The protein bound to [3H]-N6-(Δ2-isopentenyl) adenosine trialcohol. On Sephadex G-50 chromatography it gave 2 peaks corresponding to molecular weight 4000 and 8000 daltons. On sodium dodecyl sulphate-polyacrylamide gel electrophoresis, it gave only one band with an apparent molecular weight of 4000 daltons.

Formant extraction from linear-prediction phase spectra

Extraction of formant information from linear-prediction phase spectra is proposed. It is shown that the derivative of phase spectrum gives reliable formant information. Since the phase spectra for several resonators in cascade are additive, the resonance peaks are additive in the derivative of the phase spectrum unlike in the magnitude spectrum and hence the problem of identifying merged peaks is very easily solved by this method. Application of the method is illustrated through examples of linear-prediction spectra obtained for simulated models and for actural speech segments.

Synthesis and enhanced green photoluminescence emission from BCT ZnS nanocrystals

Body-centered-tetragonal (BCT) ZnS nanocrystals have been synthesized, for the first time to the best of our knowledge, by using the chemical coprecipitation method at higher synthesis temperatures of 65 and 95 degrees C. It is confirmed from X-ray diffraction (XRD) studies that in the high-temperature-synthesized samples, cubic and BCT phases coexist, in contrast to the room-temperature-synthesized sample, which consists of only cubic phase with sizes of the particles lying between 2 and 3 nm. The sizes of BCT phase nanocrystals are bigger than those of cubic phase of ZnS. The presence of BCT phase of ZnS in the samples is increased from 40 to 90% when the temperature of synthesis is increased from 65 to 95 degrees C. The nanocrystalline nature and UV-Vis absorption characteristics of the prepared samples have been studied with a transmission electron microscope (TEM) and a UV-Visible pectrophotometer, respectively. The room-temperature-synthesized ZnS sample shows photoluminescence (PL) emission in the blue region with multiple peaks, whereas the high-temperature-synthesized samples show PL emissions in the visible region. The Gaussian fittings of the measured PL spectra shows that three PL peaks at 429, 477, and 525 nm are appeared in the 65 degrees C sample and two peaks at 491 and 540 nm appear in the 95 degrees C sample with the enhanced PL intensity of the green peak at 540 nm. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim