MHD boundary layer flow of Casson fluid passing through an exponentially stretching permeable surface with thermal radiation

This article numerically examines the boundary layer flow due to an exponentially stretching surface in the presence of an applied magnetic field. Casson fluid model is used to characterize the non-Newtonian fluid behavior. The flow is subjected to suction/blowing at the surface. Analysis is carded out in presence of thermal radiation and prescribed surface heat flux. In this study, an exponential order stretching velocity and prescribed exponential order surface heat flux are accorded with each other. The governing partial differential equations are first converted into nonlinear ordinary differential equations by using appropriate transformations and then solved numerically. The effect of increasing values of the Casson parameter is to suppress the velocity field. However the temperature is enhanced when Casson parameter increases. It is found that the skin-friction coefficient increases with increasing values of suction parameter. Temperature also increases for large values of power index n in both suction and blowing cases at the boundary. It is observed that the thermal radiation enhances the effective thermal diffusivity and hence the temperature rises.     

Spectral Studies on the Binding Behavior of Cationic Dyes and Surfactants with Bacterial Polysaccharide of Klebsiella K43

The binding behavior of acidic capsular polysaccharide (SPS), isolated from Klebsiella serotype K43, with oppositely charged dyes and surfactants have been studied by way of absorbance and emission spectroscopic measurements. Each repeating unit of the SPS consists of three D-mannose, one D-galactose, and one D-glucuronic acid residue. The anionic polysaccharide exhibited chromotropic character and induced strong metachromasy in the cationic dye, pinacyanol chloride (PCYN) through the formation of a 1:1 stoichiometric complex. Evaluation of thermodynamic parameters, viz., changes in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS), for the formation of dye-polymer complex and studies on the effect of different cosolvents were also evaluated to shed light on the binding nature as well as the extent of stability of the dye-polymer complex. Fluorescence of the cationic dye acridine orange (AO) was quenched with the progressive addition of SPS, which was found to be of Stern-Volmer type. Cationic surfactants in their pure form as well as in the mixed state with nonionic surfactant (Tween-20), replaced the dye bound to the polymer matrices; thus the original band intensities of the dyes could be reverted. Such studies revealed the involvement of both electrostatic as well as hydrophobic interactions between the dye-polymer as well as surfactant-polymer aggregates.     

Random UV Mutagenesis Approach for Enhanced Biodegradation of Sulfonated Azo Dye, Green HE4B

The objective of the study was to execute mutant bacteria for efficient biodegradation of sulfonated azo dye, Green HE4B (GHE4B). UV irradiation was used to introduce random mutations in Pseudomonas sp. LBC1. Genetic alterations induced by UV irradiation in selected mutant bacteria were confirmed by random amplification of polymorphic DNA technique. The mutant bacteria named as Pseudomonas sp. 1 F reduced the time required for complete degradation of recalcitrant dye GHE4B by 25 % when compared with the wild one. The biodegradation was monitored by UV–Vis spectrophotometric analysis. Activities of enzymes like laccase, lignin peroxidase, veratryl alcohol oxidase, and NADH dichlorophenol indophenol reductase were found to be boosted in mutant bacteria as a consequence of UV-induced mutation. Matrix-assisted laser desorption/ionization-time of flight analysis of differentially expressed proteins of mutant bacteria suggested active role of antioxidant enzymes in the degradation of the dye. The degradation product was analyzed by Fourier transform infrared spectroscopy, high-performance thin-layer chromatography, and gas chromatography–mass spectrometry. Results revealed few variations in the degradation end products of wild-type and mutant bacteria. Phytotoxicity study underlined the safer biodegradation of GHE4B by mutant Pseudomonas sp. 1 F.     

A Knowledge-Based Approach for Identification of Drugs Against Vivapain-2 Protein of Plasmodium vivax Through Pharmacophore-Based Virtual Screening with Comparative Modelling

Malaria is one of the most infectious diseases in the world. Plasmodium vivax, the pathogen causing endemic malaria in humans worldwide, is responsible for extensive disease morbidity. Due to the emergence of resistance to common anti-malarial drugs, there is a continuous need to develop a new class of drugs for this pathogen. P. vivax cysteine protease, also known as vivapain-2, plays an important role in haemoglobin hydrolysis and is considered essential for the survival of the parasite. The three-dimensional (3D) structure of vivapain-2 is not predicted experimentally, so its structure is modelled by using comparative modelling approach and further validated by Qualitative Model Energy Analysis (QMEAN) and RAMPAGE tools. The potential binding site of selected vivapain-2 structure has been detected by grid-based function prediction method. Drug targets and their respective drugs similar to vivapain-2 have been identified using three publicly available databases: STITCH 3.1, DrugBank and Therapeutic Target Database (TTD). The second approach of this work focuses on docking study of selected drug E-64 against vivapain-2 protein. Docking reveals crucial information about key residues (Asn281, Cys283, Val396 and Asp398) that are responsible for holding the ligand in the active site. The similarity-search criterion is used for the preparation of our in-house database of drugs, obtained from filtering the drugs from the DrugBank database. A five-point 3D pharmacophore model is generated for the docked complex of vivapain-2 with E-64. This study of 3D pharmacophore-based virtual screening results in identifying three new drugs, amongst which one is approved and the other two are experimentally proved. The ADMET properties of these drugs are found to be in the desired range. These drugs with novel scaffolds may act as potent drugs for treating malaria caused by P. vivax.     

Dielectrophoretic separation of micron and submicron particles: A review

This paper provides an overview on separation of micron and submicron sized biological (cells, yeast, virus, bacteria, etc.) and nonbiological particles (latex, polystyrene, CNTs, metals, etc.) by dielectrophoresis (DEP), which finds wide applications in the field of medical and environmental science. Mathematical models to predict the electric field, flow profile, and concentration profiles of the particles under the influence of DEP force have also been covered in this review. In addition, advancements made primarily in the last decade, in the area of electrode design (shape and arrangement), new materials for electrode (carbon, silicon, polymers), and geometry of the microdevice, for efficient DEP separation of particles have been highlighted.     

A 2‐Tyr‐1‐carboxylate Mononuclear Iron Center Forms the Active Site of a Paracoccus Dimethylformamidase

N,N‐dimethyl formamide (DMF) is an extensively used organic solvent but is also a potent pollutant. Certain bacterial species from genera such as Paracoccus, Pseudomonas, and Alcaligenes have evolved to use DMF as a sole carbon and nitrogen source for growth via degradation by a dimethylformamidase (DMFase). We show that DMFase from Paracoccus sp. strain DMF is a halophilic and thermostable enzyme comprising a multimeric complex of the α₂β₂ or (α₂β₂)₂ type. One of the three domains of the large subunit and the small subunit are hitherto undescribed protein folds of unknown evolutionary origin. The active site consists of a mononuclear iron coordinated by two Tyr side‐chain phenolates and one carboxylate from Glu. The Fe³⁺ ion in the active site catalyzes the hydrolytic cleavage of the amide bond in DMF. Kinetic characterization reveals that the enzyme shows cooperativity between subunits, and mutagenesis and structural data provide clues to the catalytic mechanism.     

Unraveling the Origin of Differentiable ‘Turn-On’ Fluorescence Sensing of Zn2+ and Cd2+ Ions with Squaramides

A squaramide ring conjugated with Schiff-bases decorated with hydroxy and methoxy functional groups differentially senses zinc and cadmium ions, which turn on the fluorescence. The feebly emitting free ligands light up in the presence of zinc and cadmium acetates, with the acetate ion playing a pivotal role as a conjugate anion. The selective and differentiable emission responses for zinc and cadmium ions make these ligands efficient multi-analyte sensing agents. Furthermore, these ligands could be used to differentially sense zinc and cadmium ions even in aqueous environments. The NMR investigations reveal marginal differences in the binding of zinc and cadmium ions to the ligands, whereas density functional theory calculations suggest the different extent of ligand-to-metal charge transfer (LMCT) contributes to the differential behavior. Finally, comparison of the excited-state dynamics of free ligand and the metal complexes reveal the appearance of longer lifetime (about 500–700 ps) component with complexation, due to rigidified molecular skeleton, thereby impeding the non-radiative processes.