Trypsin from viscera of Indian mackerel (Rastralliger kanagurta) was purified by ammonium sulphate precipitation and chromatographic techniques such as size exclusion, ion exchange, and affinity chromatography, with a 14.4-fold increase in specific activity and 18.7% recovery. The molecular weight of the trypsin was estimated to be approximately 26 kDa using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Purified trypsin showed amidase-specific activity which was determined using benzoyl-dl-arginine-p-nitroanilide (BAPNA). The optimum pH and temperature for isolated trypsin activity were 9.0 and 50°C, respectively. The purified trypsin was strongly inhibited by soybean trypsin inhibitor (SBTI) and N-p-tosyl-1-lysine chloromethyl ketone (TLCK). Purified trypsin showed almost 40% recovery at high NaCl concentration (30%). The N-terminal amino acid sequence of the first 10 amino acids of purified trypsin was IVGGYESQPH. The Michaelis-Menten constant (K_m) and catalytic constant (K_cat) of purified trypsin were 0.430 mM and 0.77 s⁻¹, respectively, determined using BAPNA as a substrate. Purified trypsin showed digestion of casein similar to bovine trypsin by the fluorometric method.

The title hydrate, C₁₃H₁₀ClN₃O·H₂O, is the orthorhombic polymorph of the previously reported monoclinic compound [Fun et al. (2012). Acta Cryst. E68, o2303–o2304). In the title compound, the dihedral angle between the pyridine and benzene rings is 18.0 (2)°. In the crystal, the Schiff base molecules and water molecules are linked via O—H...O, N—H...O and O—H...N hydrogen bonds, forming a two-dimensional network parallel to (001). In addition, the Schiff base molecules are linked end-to-end by weak C—H...Cl hydrogen along the c-axis direction, forming an overall three-dimensional network. Weak C—H...π interactions are also observed.

Pure and Eu³⁺ ions (1, 3, 5 atomic wt%) doped ZnO nanostructures are synthesized by a surfactant assisted hydrothermal method. The effect of doping concentrations on structural, morphological and optical properties of ZnO nanostructures is studied. The XRD analysis shows good crystallinity and the phase purity of the ZnO nanostructures. A shift in the standard Zn-O stretching mode after Eu³⁺ doping is observed in the FTIR spectra. The images of FESEM demonstrate the morphological variations from hexagonal nanorods to nanoflowers on varying the dopant concentrations. Substitution of Eu³⁺ ions into Zn²⁺ sites is confirmed by EDX analysis. The dominance of particle shape over the UV-Visible absorption properties of the prepared samples is noticed. The photoluminescence (PL) emission of undoped and doped ZnO nanostructures show dominant near band edge emission (NBE) in the UV region and minor defect induced deep level emissions in the visible region.