Hydrogenation of nitroaromatics to anilines catalyzed by air‐stable arene ruthenium (II)–NNN pincer complexes

A series of air‐stable, phosphine‐free arene ruthenium (II)–NNN pincer complexes (RuL, RuL¹, RuL² and RuL³) have been synthesized and characterized by spectroscopic and single‐crystal X‐ray analysis. Further, arene ruthenium (II)–NNN pincer complexes have been used as catalyst for hydrogenation of nitroaromatics into aniline in the presence of NaBH₄ at room temperature. The catalytic process suggested highly chemo‐selective nitroreduction with wide functional group tolerance.     

Facile Production and Rapid Purification of Functional Recombinant Qβ Replicase Heterotetramer Complex

We describe an improved method for the production of recombinant Qβ replicase heterotetramer. The successful expression of the soluble Qβ RNA polymerase complex depends on the EF-Ts and EF-Tu subunits being co-expressed prior to β-subunit expression. Efficient co-expression requires two different inducible operons to co-ordinate the expression of the heterotrimer. The complete heterotetramer enzyme complex is achieved by production of the recombinant S1-subunit of Qβ replicase in a separate host. This approach represents a facile way for producing and purifying large amounts of soluble and active recombinant Qβ replicase tetramer without the necessity of a His-tag for purification.     

Biological Real-Time Reaction Calorimeter Studies for the Production of Penicillin G Acylase from Bacillus badius

Penicillin G acylase (PGA) is a commercially important enzyme that cleaves penicillin G to 6-amino penicillanic acid (6-APA) and phenyl acetic acid (PAA). The strain Bacillus badius has been identified as potential producer of PGA. A detailed calorimetric investigation on PGA production was carried out to enable generation of thermokinetic data possible for commercial application. Reaction calorimetric studies coupled with respirometric studies suggested that enzyme activity of the species B. badius was calorimetrically traceable. Three phases of growth were distinctly noticeable in the metabolic heat-time curve. Increase in enzymatic activity with restricted growth confirmed intracellular nature of the production process. The estimated heat yields due to biomass growth, 10.026 kJ/g, substrate consumption 22.761 kJ/g, and oxygen uptake 383?±?10 kJ/mol helped to understand the energetic of the organism under study. Low oxycalorific coefficient confirmed the existence of fermentation-coupled metabolism of B. badius.     

Acoustic and Thermodynamic Properties of Binary Liquid Mixtures of Benzaldehyde in Hexane and Cyclohexane

Densities and ultrasonic speeds of binary mixtures of benzaldehyde with n-hexane and cyclohexane at 30 °C were measured over the entire composition range. From these experimental data, the adiabatic compressibility (K _S ), intermolecular free length (L _f), acoustic impedance (Z), relative association (R _a) and relaxation strength (r) were calculated. Also, the excess adiabatic compressibility (K _S ^E), intermolecular free length (L _f^E), acoustic impedance (Z ^E), and ultrasonic velocity (U ^E) were calculated. The observed variation of these parameters helps in understanding the nature of interactions in these mixtures. Further, theoretical values of the ultrasonic speed were evaluated using theories and empirical relations. The relative merits of these theories and relations were discussed.     

Non-Heme-Iron-Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds

Oxidation of the iron(II) precursor [(L¹)Fe^IICl₂], where L¹ is a tetradentate bispidine, with soluble iodosylbenzene (^sPhIO) leads to the extremely reactive ferryl oxidant [(L¹)(Cl)Fe^IV=O]⁺ with a cis disposition of the chlorido and oxido coligands, as observed in non-heme halogenase enzymes. Experimental data indicate that, with cyclohexane as substrate, there is selective formation of chlorocyclohexane, the halogenation being initiated by C−H abstraction and the result of a rebound of the ensuing radical to an iron-bound Cl⁻. The time-resolved formation of the halogenation product indicates that this primarily results from ^sPhIO oxidation of an initially formed oxido-bridged diiron(III) resting state. The high yield of up to >70 % (stoichiometric reaction) as well as the differing reactivities of free Fe²⁺ and Fe³⁺ in comparison with [(L¹)Fe^IICl₂] indicate a high complex stability of the bispidine-iron complexes. DFT analysis shows that, due to a large driving force and small triplet-quintet gap, [(L¹)(Cl)Fe^IV=O]⁺ is the most reactive small-molecule halogenase model, that the Fe^III/radical rebound intermediate has a relatively long lifetime (as supported by experimentally observed cage escape), and that this intermediate has, as observed experimentally, a lower energy barrier to the halogenation than the hydroxylation product; this is shown to primarily be due to steric effects.     

Molecular docking approach on the molecular interactions involving beta-lactoglobulin (βLG)-4-Dicyanomethylene2,6-Dimethyl-4-Hpyran (DDP) dye in the presence of an antibiotic,norfloxacin

Molecular docking (MD) techniques were employed in the determination of binding stability of Beta-lactoglobulin (βLG) with 4-Dicyanomethylene2,6-Dimethyl-4-Hpyran (DDP) dye in the presence of quinolone-based antibiotic, norfloxacin (NOR). βLG acts as the host and drug/dye is employed as the guest molecule. The energetics and molecular interaction parameters of βLG-DDP were found to be stable than βLG-NOR. DDP resides in three distinguishably different binding sites of βLG, however the binding energies does not differ considerably. Interestingly, the energetics of βLG-NOR conformers differs significantly and reveals the existence of two distinguishable conformers. NOR acts as a hydrogen-bonding (HB) acceptor and the amino acid (AA) residues of βLG as the donor. The extent of HB interactions predominates over hydrophobic interactions in βLG-NOR than βLG-DDP complex. MD studies authenticates no direct binding of dye-drug inside the domains of βLG, when docked simultaneously. On the contrary, docking of dye to βLG-NOR complex enhances the binding stability. Several molecular interactions govern the stability of the complex and play a major role on the binding affinity of the host-guest complex in the presence of two competitive ligands. MD techniques authenticate that DDP/NOR is bound to several AA residues through conventional and non-conventional HB interactions accompanied with hydrophobic, pi-pi, pi-alkyl and van der Waals forces of interactions. Further, MD methods is employed as an efficient tool and a non-evasive technique in establishing the stability of 1:1complex of drug/dye with βLG in the present study.     

Partially Oxidized Graphene/Metallic Single‐Walled Carbon Nanotubes Film‐Coated Electrode for Nanomolar Detection of Dopamine

Enriched metallic single‐walled carbon nanotubes (mSWCNTs) were dispersed in aqueous solution of partially oxidized graphene (po‐Gr). As‐prepared po‐Gr/mSWCNTs suspension was used to modify glassy carbon electrode (GCE) surface, which showed high electrocatalytic activity for dopamine (DA) oxidation in pH 7.0 phosphate buffered saline (PBS) solution. Using po‐Gr/mSWCNTs/GCE we could detect DA from 350 to 3600 nM, with a detection limit down to 25 nM in physiological condition (in pH 7.0 PBS); whereas, po‐Gr/GCE (without mSWCNTs) and bare GCE produced measurable signals only at or above 200 nM DA. Thus, the po‐Gr/mSWCNTs film we fabricated is a promising nanomaterial for fabrication of biosensors for nanomolar detection of DA.     

Reduced Graphene Oxide/Carbon Nanotube/Gold Nanoparticles Nanocomposite Functionalized Screen‐Printed Electrode for Sensitive Electrochemical Detection of Endocrine Disruptor Bisphenol A

We fabricated a highly sensitive electrochemical sensor for the determination of bisphenol A (BPA) in aqueous solution by using reduced graphene oxide (RGO), carbon nanotubes (CNT), and gold nanoparticles (AuNPs)‐modified screen‐printed electrode (SPE). GO/CNT nanocomposite was directly reduced to RGO/CNT on SPE at room temperature. AuNPs were then electrochemically deposited in situ on RGO/CNT‐modified SPE. Under optimized conditions, differential pulse voltammetry (DPV) produced linear current responses for BPA concentrations of 1.45 to 20 and 20 to 1,490 nM, with a calculated detection limit of an ultralow 800 pM. The sensor response was unaffected by the presence of interferents such as phenol, p‐nitrophenol, pyrocatechol, 2,4‐dinitrophenol, and hydroquinone.