On single courier problem

A new set of NP problems defined as Courier Problems that is motivated from the requirements in railway wagon scheduling is proposed. The general version includes many mobile couriers. The simplest version of this will consider a single courier. An algorithm to transform the single courier problem into a traveling salesman problem is presented.     

Chemical synthesis of mesoporous CuO from a single precursor: Structural, optical and electrical properties

We report a simple method for growing photoluminescent mesoporous CuO nanoparticles by a chemical route, using the single precursor technique. The final products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), N₂ adsorption-desorption isotherm, UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and Hall measurements. Structural analysis reveals that the average pore diameter of the as-prepared CuO is about 38.8 Å and it comes with an average surface area of 66.63 m²/g. N₂-sorption analysis shows that the resulting isotherm as type IV; which is the characteristic of mesoporous materials. The average crystal diameter, as derived from the XRD data analysis is found to be about 20 nm. FESEM measurement reveals that the material is composed of cubic nanoparticles. The UV-vis spectrum of the material shows significant amount of blue-shift in the band gap energy (E_g), due to the quantum confinement effect exerted by the nanocrystals. The Raman study of the CuO nanostructures also indicates the high crystalline nature of the material. From the positive sign of Hall coefficient, the p-type conduction nature of the deposited film is established. The film was found to show high magnetoresistance, which is in the order of 10⁵ Ω.     

Supramolecular self-assembled chaos: polyphenolic lignin's barrier to cost-effective lignocellulosic biofuels

Phenylpropanoid metabolism yields a mixture of monolignols that undergo chaotic, non-enzymatic reactions such as free radical polymerization and spontaneous self-assembly in order to form the polyphenolic lignin which is a barrier to cost-effective lignocellulosic biofuels. Post-synthesis lignin integration into the plant cell wall is unclear, including how the hydrophobic lignin incorporates into the wall in an initially hydrophilic milieu. Self-assembly, self-organization and aggregation give rise to a complex, 3D network of lignin that displays randomly branched topology and fractal properties. Attempts at isolating lignin, analogous to archaeology, are instantly destructive and non-representative of in planta. Lack of plant ligninases or enzymes that hydrolyze specific bonds in lignin-carbohydrate complexes (LCCs) also frustrate a better grasp of lignin. Supramolecular self-assembly, nano-mechanical properties of lignin-lignin, lignin-polysaccharide interactions and association-dissociation kinetics affect biomass deconstruction and thereby cost-effective biofuels production.     

Dereplication coupled with in vitro antioxidant assay of two flavonoid glycosides from Diospyros peregrina fruit

Diospyros peregrina is an edible seasonal fruit found in coastal West Bengal, India. The fruits have been reported to possess a significant antioxidant activity. In this study, the aim was to isolate the lead compound responsible for the above-mentioned activity. The aqueous extract of D. peregrina fruit was subjected to dereplication coupled with an in?vitro 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay. The n-butanol fraction of the aqueous extract of D. peregrina fruit exhibited significant antioxidant activity (IC(50), 131.10?μg?mL(-1)) as compared with the parent extract (IC(50), 285.15?μg?mL(-1)). The n-butanol fraction was subjected to silica gel column chromatographic separation coupled with a chemo-autographic study of column eluents, employing ethanolic DPPH as a spraying reagent. Two bioactive flavonoid glycosides, namely luteoline-4'-methyl-ether-7-O-glucoside and quercetin-3-O-(glucosyl)-glucoside, were identified to exhibit IC(50) values of 74.04 and 65.78?μg?mL(-1), respectively in the DPPH assay.     

Enantioselective cyclopropanation of enals by oxidative N-heterocyclic carbene catalysis

Carbene catalysed redox activation of α,β-unsaturated aldehydes is applied for generation of α,β-unsaturated acyl azoliums which undergo cyclopropanation upon reaction with a sulfur ylide and an alcohol to give the corresponding cyclopropanecarboxylic acid esters. With chiral carbenes good to excellent diastereo and enantioselectivities are obtained.     

Comparative study of the semiconducting properties of benzothiadiazole and benzobis(thiadiazole) derivatives using computational techniques

Recent literature reports indicate that derivatives of benzothiadiazole (BT) and benzobis(thiadiazole) (BBT), which differs from BT by an extra thiadiazole ring, exhibit good semiconducting properties, such as high electron mobility and low-lying lowest unoccupied molecular-orbital (LUMO) levels. In this study herein, computational techniques like density functional theory (DFT), spin-flip DFT and valence-bond methods are used to analyze the semiconducting properties of these molecules. Calculations at the B3LYP/cc-pVTZ level reveal that all the BBT molecules, including the bare BBT ring, have lower lying LUMO energies (3.70-4.11 eV) compared to the BT derivatives (2.56-3.41 eV) with similar substitution. The reorganization energies (λ(+)/λ(-)) obtained at this level of theory of the BT derivatives are around (225-333)/(246-315) meV, while BBT derivatives have much smaller reorganization energies and these are in the range of (129-259)/(150-230) meV. We observe that the different behavior of BBT is due to the inherited biradicaloid character from the parent molecule tetramethylenebenzene (TMB), a disjoint non-Kekule biradical having non-bonding molecular orbitals (NBMOs) as the highest occupied molecular orbital (HOMO) and LUMO. Additionally, the perturbation of the orbitals of the biradical TMB to obtain BBT is the major cause for the BBT derivatives to have a larger electron affinity (EA) and a smaller HOMO-LUMO gap (HLG) compared to BT derivatives.     

A novel Bicine running buffer system for doubled sodium dodecyl sulfate - polyacrylamide gel electrophoresis of membrane proteins

A novel, Bicine-based SDS-PAGE buffer system was developed for the analysis of membrane proteins. The method involves molecular weight-based separations of fully denatured and solubilized proteins in two dimensions. This doubled SDS-PAGE (dSDS-PAGE) approach produced a diagonal arrangement of protein spots and successfully circumvented problems associated with membrane proteome analysis involving traditional gel-based methods. Membrane proteins from the anaerobic bacterium Clostridium thermocellum were used for these investigations. Tricine-dSDS-PAGE and the newly developed Bicine-dSDS-PAGE were compared with the standard glycine-dSDS-PAGE (Laemmli protocol) in their suitability to separate C. thermocellum membrane proteins. Large-format gel experiments using optimized gel preparation and running buffer conditions revealed a 112% increase in protein spot count for Tricine-dSDS-PAGE and a 151% increase for Bicine-dSDS-PAGE, compared to glycine-dSDS-PAGE. The data clearly indicated that Bicine-dSDS-PAGE is a superior method for the analysis of membrane proteins, providing enhanced resolution and protein representation.     

New limits for solid-state 17O NMR spectroscopy: complete resolution of multiple oxygen sites in a simple biomolecule

A solid-state 17O NMR 1H-decoupled double angle rotation (DOR) study of monosodium l-glutamate monohydrate (l-MSG) is reported. It is shown that all eight inequivalent sites can be resolved with DOR line widths ( approximately 65 Hz) approximately 120 times narrower than those in the MAS spectrum. The lines are tentatively assigned on the basis of their behavior under proton decoupling and the isotropic chemical shift and the quadrupole interaction parameter for each extracted by a combination of DOR and 3Q MAS at variable magnetic fields. With a shift range of approximately 45 ppm for these similar oxygen sites and spectral resolution under DOR comparable to that for spin-1/2 nuclei, solid-state 17O NMR should have tremendous potential in the study of biomolecules.