Jaspreet S. Dhau

A Study on the Antioxidant Activity of Pyridylselenium Compounds and their Slow Release from Poly(acrylamide) Hydrogels

Abstract The antioxidant activity of pyridylselenium compounds has been evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and nitric oxide (NO) scavenging methods. Pyridylselenium compounds have shown far superior (100–1000 times) antioxidant property than ebselen. The control release of bis(2-pyridyl) diselenide from poly(acrylamide) hydrogels has been studied in order to evaluate its release mechanism and diffusion coefficient. The later study also demonstrates that the pyridylselenium loading into the polymer matrix increases the magnitude and the rate of the radical scavenging activity of the poly(acrylamide) hydrogels. GRAPHICAL ABSTRACT

Covalent linkage of alkalothermophilic catalase onto functionalized cellulose

Catalase from a thermophilic bacterium belonging to the genus Geobacillus was purified and covalently immobilized onto a functionalized polymer via a spacer with an objective to improve its kinetic and biochemical properties. This is the first report on the purification and immobilization of catalase from the genus Geobacillus. The tetrameric catalase of about 221 kDa was successfully purified using a multistep purification strategy. A shift in pH and temperature optima from 8.0 to 9.0 and 55 °C to 60 °C, respectively was recorded after covalent binding of catalase onto the functionalized matrix. The kinetic constants i.e. Km, Vmax, Kcat and Kcat/Km were found to be 1.2 mM, 4.43 × 106 IU, 6.3 × 105 s−1 and 5.25 × 108 s−1 M−1 for free, and 1.8 mM, 4.01 × 106 IU, 5.9 × 105 s−1 and 3.20 × 108 s−1 M−1 for immobilized catalase, respectively. The ease of binding of alkalothermophilic catalase from a novel isolated bacterium G. extremocatsoochus sp. nov., MTCC 5873 onto a low cost activated cellulose support demonstrated enhanced pH and thermal stability as compared to its free counterpart. This immobilized catalase preparation with improved characteristics has good potential for diverse applications. The present findings provide valuable information on how to tailor enzymes and supported polymer matrices to improve the performance of a biocatalyst.

A mechanistic study of the synthesis, single crystal X-ray data and anticarcinogenic potential of bis(2-pyridyl)selenides and -diselenides

The reaction of bis(organyl)diselenide with a reducing agent, such as LiAlH4, NaBH4, Li(C2H5)3BH, etc., generally leads to cleavage of the Se–Se bond resulting in the formation of the corresponding organylselenols/selenolates. However, this work for the first time demonstrates the scisson of the C(pyridine)–Se bond in bis(2-pyridyl)diselenides with LiAlH4. The reaction affords analytically pure bis(2-pyridyl)selenides in near quantitative yields. The reaction pathway involves the formation of a selenated aluminato complex followed by the scission of the C(pyridine)–Se bond and generation of LiAlSeH2. The generation of LiAlSeH2 was established by experimental and NMR analysis. The mechanism of the reaction has been supported by theoretical analysis. Single crystal X-ray structure determination of bis(3-methyl-2-pyridyl)selenide (2e) was performed and it shows that the molecules are self-assembled in a 2D-network of C–H⋯N hydrogen bonds and π⋯π stacking interactions. The synthesized compounds were also evaluated against the Raji cancer cell line (acute lymphoid leukemia).

Metallosurfactant based Pd–Ni alloy nanoparticles as a proficient catalyst in the Mizoroki Heck coupling reaction

A highly efficient, operationally simple and green catalytic approach involving Pd–Ni alloy nanoparticles (NPs) has been developed using microwaves (MWs) as an energy source and water–ethanol as a solvent system. Metallosurfactants were synthesized and used as precursors to fabricate Pd–Ni alloy NPs with a good control over the size and morphology. Surfactant capped zerovalent Pd–Ni alloy NPs were fabricated in the metallomicellar cores by a two-phase reduction method. The synthesized NPs exhibited the highest catalytic efficiency for the stereoselective Mizoroki Heck coupling featuring short reaction time, mild reaction conditions, wide substrate scope, preclusion of toxic organic solvents, easy recovery and recyclability of the catalyst.

Wastewater cleanup using Phlebia acerina fungi: An insight into mycoremediation

The scarcity of available drinking water has led the researchers to develop novel and cost-effective ways of bioremediation process for wastewater treatment. Bioremediation is a cost-effective and environmentally sound method for the removal of toxic compounds. Such approach is not only a chemical-less effort but also an energy savior. In the present work Phlebia acerina, a white rot wood rotting fungi have been used to degrade the toxic wastewater pollutants. Congo Red (CR) and Eriochrome Black T (EBT) have been selected as model pollutants to test the wastewater cleaning ability of the fungus. The Lignin modifying enzyme (LME) and Cellulolytic enzyme assays (CMC) potential of Phlebia acerina helped in understanding the dye degradation mechanism. Under the optimum conditions, the fungi was able to degrade as high as 92.4% CR while the EBT was degraded to a maximum of 50%. Phlebia acerina was found to show first-order kinetics of dyes degradation. Further, the seed germination and antimicrobial assay of treated and untreated water were carried out in order to establish the formation of non-toxic end product after degradation.

FT-IR, NMR, molecular structure, and HOMO-LUMO studies of 3,5-dimethyl-2-pyridylselenium compounds by density functional theory

GRAPHICAL ABSTRACT ABSTRACT The present study explores various quantum chemical models to better understand the molecular properties of pyridylselenium compounds. We have carried out theoretical and experimental analyses of bis(3,5-dimethyl-2-pyridyl)diselenide (1), 3,5-dimethyl-2,6-bis(methylselenenyl) pyridine (2) and 3,5-dimethyl-2-(methylselenenyl)pyridine (3). The study demonstrates the effect of structural variations on molecular properties of these compounds. Density functional theory (DFT) has been used to calculate vibrational wavenumbers and intensity of vibrational bands and the results obtained are in excellent agreement with the experimental FT-IR data. The 1H and 13C NMR chemical shifts were calculated using GIAO method in gas phase and solvent phase of CDCl3 by taking IEFPCM method and correlations have been developed which accurately predicts the chemical shift values of various organoselenium compounds. The HOMO-LUMO energies in the gas and solvent phase were calculated by using B3LYP/6-311++G(d,p) level of theory. The HOMO-LUMO energy gaps in different molecules were compared and correlated with their biological activity.