Purification,characterization, antibacterial activity and N-terminal sequencing of buffalo-milk lysozyme

Lysozyme from buffalo milk was purified to homogeneity and its N-terminal amino acid sequence, biochemical properties and antibacterial spectrum were determined. The purification procedure, comprising ion-exchange chromatography using CM-cellulose and size-exclusion chromatography using Sephadex G-50, conferred 8622-fold purification and 39.3% recovery of lysozyme. The purified enzyme migrated as a single band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and native PAGE. Immunological purity of lysozyme preparation was confirmed by immuno-electrophoresis. Molecular weight of buffalo-milk lysozyme as determined by SDS-PAGE was 16 kDa and its amino acid composition was determined by reverse phase high performance liquid chromatography (HPLC). The sequence of 23 amino acid residues at the N-terminal end showed 56.5% homology with bovine milk lysozyme and 30.4% with equine milk lysozyme. The specific activity of buffalo milk lysozyme was ten-times that of bovine milk lysozyme. Buffalo-milk lysozyme was active over a wide range of pH and its activity was strongly influenced by molarity of the medium. Antibacterial activity of buffalo-milk lysozyme was determined against 11 species of bacteria; out of seven Gram-positive bacteria tested, four were inhibited, while Gram-negative bacteria were resistant.     

Microstructure and growth of ZnTe films

The microstructure and growth of ZnTe films deposited onto glass and freshly cleaved NaCl substrates are carefully studied by a TEM. Effect of different stimulator on the grain growth is also described.     

Systematic hardness measurements on some rare earth garnet crystal

Microhardness measurements were undertaken on twelve rare earth garnet crystals. In yttrium aluminium garnet and gadolinium gallium garnet, there was no measurable difference in the hardness values of pure and nominally Nd-doped crystals. The hardness values were correlated with the lattice and elastic constants. An analysis of hardness data in terms of the interatomic binding indicated a high degree of covalency. Dedicated to the memory of Dr R Thyagarajan, eminent Solid State Physicist.     

Systematic hardness measurements on mixed and doped crystals of rubidium halides

Efforts are made to improve the hardness of rubidium halide crystals by (i) solid solution hardening and (ii) impurity hardening. Systematic microhardness measurements have been made on rubidium halide mixed crystals (RbBr-RbI and KI-RbI) and rubidium halide crystals doped with Sr²⁺ ions. The composition dependence of the hardness of mixed crystals follows the law ΔH _v =K x (1− x),where ΔH _v is the enhancement in hardness,K a constant andx and (1 −x) the concentrations of the first and second component of the mixed crystals, respectively. The hardness of doped crystals increases with the concentrationC of the dopant according to the law, ΔH _v+6 =k C ^m ,wherek andm are constants. The relative efficacy of the two methods of hardening is discussed.     

Systematic hardness measurements on CsClxBr(1?x) and NH4ClxBr(1?x) mixed crystals

Vickers hardness measurements have been made on polycrystalline blanks of CsCl _x Br_(1−x) and single crystals of NH₄Cl _x Br_(1−x). The composition dependence of hardness is highly nonlinear in both systems and follows an empirical model that includes a lattice contribution and a disorder contribution. The Gilman-Chin parameter (H/C ₄₄) has been calculated and its significance discussed.     

Heat transfer in boundary layer flow of a micropolar fluid past a curved surface with suction and injection

Van Dyke's singular perturbation technique has been used to study the heat transfer in the flow of a micropolar fluid past a curved surface with suction and injection. The conditions for similar solutions of the thermal boundary layer equations have been obtained. In addition to the usual “no slip” condition for velocity, the two types of boundary conditions used for microrotation are: (i) no relative spin on the boundary; (ii) the anti-symmetric part of the stress tensor vanishes at the boundary. The effect of suction or injection on velocity, microrotation, temperature, skin friction coefficient, wall couple stress coefficient, displacement and momentum thicknesses, rate of heat transfer and adiabatic wall temperature have been studied. It is observed that with the increase of injection velocity, the thickness of the boundary layer is increased and the local drag is reduced. A comparison with the results obtained for a Newtonian fluid reveals that the microelements present in the fluid reduce the velocity and frictional drag, and cool the boundary.     

Consistency checks on elastic properties of crystals

Several methods are available for the determination of the bulk modulus of solids and single crystal elastic constants. Although high accuracy is claimed, cases exist where the values of the elastic properties reported by different workers using different or same methods show differences far beyond the claimed limits of experimental errors. More than two dozen cases are cited where the differences in the reported values of the bulk moduli are of the order of 20% or more; in some cases the differences are as much as a factor of 3–5. Similarly, nearly a dozen cases are cited where the single crystal elastic constants of a crystal from different sources differ by about 20% or more and in some cases by a factor of 3–15; in fact there are cases where the reported elastic constants even differ in sign. This paper discusses a number of consistency checks for elastic properties of solids which help in sifting acceptable values from out of a wide range of reported values.Professor Emeritus     

Biomolecule assisted hydrothermal synthesis of chainlike network of silver sulfide nanostructures

A L-cysteine assisted hydrothermal route has been utilized for the growth of Ag2S nanostructures with chainlike network. It was observed that the experimental parameters such as the synthesis temperature and variation in the molar ratio of the anionic and cationic precursors play critical role in determining the morphology and crystal structure of the products. X-ray diffraction study revealed the formation of monoclinic acanthite Ag2S. L-cysteine was acting as complexing agent as well as sulfur source. The branching fractal morphology was explained through Cayley tree model and structure of L-cysteine.     

CdS:Mn nanorods: solvothermal synthesis and properties

Manganese (0.05-9 mol.%) doped CdS nanorods were synthesized via solvothermal route using ethylenediamine (En) and a mixture of En and water as the solvents. The diameters and the lengths of the doped CdS nanorods varied from 40-100 nm and 600-2500 nm, respectively, with change in the composition of the solvents. The broad photoluminescence (PL) emission from the undoped CdS nanorods centered at approximately 535 nm is found to be blue shifted to 516 nm with the incorporation of Mn in the CdS crystal structure. Also increase in the intensity of the PL was noticed in the Mn doped CdS nanorods for both the solvent systems. Maximum PL intensity was observed for 1 mol.% Mn in case of En system and for 0.5 mol.% Mn in case of En/water system, above which quenching occurred as a result of Mn-Mn clustering. EPR study revealed six-line hyperfine splitting for low Mn concentration in both solvent systems. Increase in the Mn concentration caused EPR signal broadening due to Mn-Mn clustering.