A Comparison of Dogfish and Bovine Chymotrypsins in Relation to Protein Hydrolysis

An extracellular protease, chymotrypsin, from a low temperature-adapted poikilotherm (dogfish) was compared with the bovine enzyme against several protein substrates to determine potential advantages in the use of an enzyme adapted to functioning in a low temperature environment. In general, the dogfish enzyme showed a higher rate of reaction and hydrolyzed more peptide bonds than did the bovine enzyme whether the substrates were soluble or insoluble proteins. Dogfish chymotrypsin was slow to produce clotting of milk, but once formed the clot had good stability. The bovine enzyme was more efficient in incorporating methionine into soy protein in a piasteintype reaction.     

PURIFICATION AND PROPERTIES OF POLYPHENOL OXIDASE FROM MANGO PEEL (MANGIFERA INDICA. VAR. RASPURI)

Polyphenol oxidase from the peel of ripe mango fruit (Mangifera indica. Var. Raspuri) was purifed 126-fold to homogeneity by ammoniun sulphate fractionation, column chromatography on Blue Sepharose CL-6B and gel chromatography on Sephadex G-200. It had an iso-electric point (pI) of 4.1±0.2 and molecular weight of 137,000 daltons as determined by sodium dodecyl sulphate—polyacrylamide gel electrophoresis and gel filtration. It was more specific for catechol (than for other substatres tested) with a Km of 8.2 mM. 2-mercaptoethanol, L-cysteine, sodium diethyldithiocarbamate and thiourea were effective inhibitors of this enzyme. It had pH and temperature optima of 5.5 and 46⁰C, respectively. It lost 50% activity by exposure to 85⁰, 75⁰ and 65⁰C for 3, 16 and 25.5 min, respectively. Copper content was one atom per mole of enzyme and copper was essential for its activity. Unlike most of the polyphenol oxidases, multiple forms were not detected in the crude extract.     

Effect of embedment length of untreated natural fibres on the bond behaviour in cement mortar

The present investigation is focused on studying the effects of various matrices with 1:3, 1:4 and 1:5 mortars and fibre types of sisal and coir on the bond behavior at various ages of curing, i.e., 24 h, 3 d, 7 d and 28 d. The other parameters included in the investigation are water/cement (w/c) ratio, sand gradation and embedment length of fibres. In addition, the type of failure of sisal and coir fibres for different mixes of mortars at various curing ages is also reported. From the results, it is seen that the bond strength is improving with respect to age of curing in case of sisal fibres, but decreases in case of coir fibres. The failure of fibres due to fibre fracture is observed in sisal fibres and fibre pullout is observed in coir fibres. The other varying parameters such as mortar mixes, sand gradation, w/c ratio and embedded length also showed significant effect on bond behaviour of sisal and coir fibre with the cement mortar mixes.     

EFFECT OF PECTIN CONTENT ON FLOW PROPERTIES OF MANGO PULP CONCENTRATES

The effect of pectin on the flow properties of mango pulp concentrates was studied using a coaxial cylindrical viscometer in the temperature (T) range 303-343°K. The variables were soluble solid content(C) 16-30°Brix, pectin content (C_pec, range 0.0323-0.0349 dry wt fraction) for the shear rate (γ) range 9.0-250 s^-1. Mango pulp concentrates behaved as pseudoplastic fluids in the entire pectin content range with a flow behaviour index of 0.286. A model relating shear stress () with the above variables is presented:     

Magnetic force microscopy and simulation studies on Co<Subscript>50</Subscript>Fe<Subscript>50</Subscript> elliptical nanomagnets

We studied the magnetization reversal mechanism of single-layered Co₅₀Fe₅₀ nanomagnets by measuring the magnetization reversal and using the micromagnetic simulations. The magnetization reversal strongly depends on the thickness of the nanomagnets. In the remanent state, the magnetic force microscopy studies and the simulation data showed the formation of single and vortex states depending on the thickness of nanomagnets.     

The asymmetric lossy near-perfect lens

We extend the ideas of the perfect lens recently proposed [J.B. Pendry, Phys. Rev. Lett. 85, 3966 (2000)] to an alternative structure. We show that a slab of a medium with negative refractive index bounded by media of different positive refractive index also amplifies evanescent waves and can act as a near-perfect lens. We examine the role of the surface states in the amplification of the evanescent waves. The image resolution obtained by this asymmetric lens is more robust against the effects of absorption in the lens. In particular, we study the case of a slab of silver, which has a negative dielectric constant, with air on one side and other media such as glass or GaAs on the other side as an ‘asymmetric’ lossy near-perfect lens for p-polarized waves. It is found that retardation has an adverse effect on the imaging due to the positive magnetic permeability of silver, but we conclude that subwavelength image resolution is possible in spite of it.     

Molecular Characterization and Comparative Sequence Analysis of Defense-Related Gene, Oryza rufipogon Receptor-Like Protein Kinase 1

Many of the plant leucine rich repeat receptor-like kinases (LRR-RLKs) have been found to regulate signaling during plant defense processes. In this study, we selected and sequenced an LRR-RLK gene, designated as Oryza rufipogon receptor-like protein kinase 1 (OrufRPK1), located within yield QTL yld1.1 from the wild rice Oryza rufipogon (accession IRGC105491). A 2055 bp coding region and two exons were identified. Southern blotting determined OrufRPK1 to be a single copy gene. Sequence comparison with cultivated rice orthologs (OsI219RPK1, OsI9311RPK1 and OsJNipponRPK1, respectively derived from O. sativa ssp. indica cv. MR219, O. sativa ssp. indica cv. 9311 and O. sativa ssp. japonica cv. Nipponbare) revealed the presence of 12 single nucleotide polymorphisms (SNPs) with five non-synonymous substitutions, and 23 insertion/deletion sites. The biological role of the OrufRPK1 as a defense related LRR-RLK is proposed on the basis of cDNA sequence characterization, domain subfamily classification, structural prediction of extra cellular domains, cluster analysis and comparative gene expression.     

Graphene composites containing chemically bonded metal oxides

Composites of graphene involving chemically bonded nano films of metal oxides have been prepared by reacting graphene containing surface oxygen functionalities with metal halide vapours followed by exposure to water vapour. The composites have been characterized by electron microscopy, atomic force microscopy and other techniques. Magnetite particles chemically bonded to graphene dispersible in various solvents have been prepared and they exhibit fairly high magnetization.     

Liquidus Relations in the Quaternary Subsystem CaAl2O3-CaAl4O7-Ca2Al2SiO7-MgAl2O4

Equilibrium diagrams for the joins CaAl₄O₇-MgAl₂O₄, CaAl₄O₄-Ca₂Al₂SiO₇-MgAl₂O₄, and Ca₂Al₂O₄–Ca₂Al₂SiO₇-MgAl₂O₄ were determined by the classical quenching method and hot stage microscopy. Liquidus relations in the quaternary subsystem are discussed. Two univariant curves are located within the composition tetrahedron. The quaternary invariant point is a peri-tectic. Technological application of results is indicated.