New synthetic strategy for Friedlander condensation of 4-amino-2-oxo-2H-chromene-3-carbaldehyde by heterogeneous catalysis

Chromenopyridines are an important class of compound because of their diverse biological activities. In the present work, we have developed convenient route for the synthesis of chromeno[4,3-b] pyridine derivatives ( 3a – e , 5a – e , and 7a – d ) by Friedlander condensation of 4-amino-2-oxo-2H-chromene-3-carbaldehyde with various active methylene compounds. We have used mixed metal oxide catalyst such as nanomaterial Zinc titanate. The reaction was carried out for various solvent systems, also we have altered the concentration of the catalyst. The 2-propanol/water solvent system and 5 mol% catalyst concentration are best as far as yield and rate of reaction are concerned. The structures of the synthesized compounds were confirmed by ¹H NMR, ¹³C NMR, mass spectra, and elemental analysis.     

On the cooperativity of cation-pi and hydrogen bonding interactions

Quantum chemical calculations are performed to gauge the effect of cation-pi and hydrogen bonding interactions on each other. M-phenol-acceptor (M = Li (+) and Mg (2+); acceptor = H(2)O, HCOOH, HCN, CH(3)OH, HCONH(2) and NH(3)) is taken as a model ternary system that exhibits the cation-pi and hydrogen bonding interactions. Cooperativity is quantified and the computed positive cooperativity between cation-pi and hydrogen bonding interactions is rationalized through reduced variational space (RVS) and charge analyses.     

Molecular model for toughening in double-network hydrogels

A molecular mechanism is proposed for the toughness enhancement observed in double-network (DN) hydrogels prepared from poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) polyelectrolyte network and poly(acrylamide) (PAAm) linear polymer. It is an extension of the phenomenological model set forth recently by Gong et al. ( Macromolecules 2007, 40, 6658- 6664 ). This mechanism rationalizes the changes in molecular structure of the DN gel constituents observed via in situ neutron scattering measurements, the composition dependence of the solution viscosity, and the thermodynamic interaction parameters of PAMPS and PAAm molecules obtained previously from neutron scattering studies. More specifically, this proposed mechanism provides an explanation for the observed periodic compositional fluctuations in the micrometer range induced by large strain deformation.     

Purification and characterization of zinc alpha2-glycoprotein-prolactin inducible protein complex from human seminal plasma

Zinc alpha2-glycoprotein (ZAG) is present at high concentration in human seminal plasma, and considered as soluble homologue of MHC-I. ZAG is a well-known biomarker for prostate and breast carcinomas. We have purified a naturally occurring complex of ZAG with Prolactin inducible protein (PIP), which is also a well-known biomarker for the same. The ZAG-PIP complex has been isolated and purified by simple chromatographic techniques in a reproducible two-step process, using ion exchange and gel-permeation chromatography and subsequently identified by MS. The complex between ZAG and PIP is formed by non-covalent interactions. The purity and molecular mass was determined by SDS-PAGE, which shows the bands corresponding to 40 kDa and 14 kDa, which were also confirmed by MALDI-TOF. Dynamic light scattering (DLS) experiments also showed hydrodynamic radii corresponding to 54, 40 and 14 kDa for ZAG-PIP complex, ZAG and PIP respectively. The concentration dependent aggregation of this complex has also been observed. Fluorescence analysis reveals that complexes have similar binding affinities as native ZAG, for their proposed ligands like arachidonic acid, polyethylene glycol and synthetic peptide. This is the first report on purification and characterization of a naturally occurring complex of ZAG-PIP in human seminal fluid.     

A versatile synthesis of 2,4-substituted oxazoles

A variety of five-membered ring oxazoles have been synthesised with complete regiocontrol and without the requirement for ring oxidation via a reaction sequence based on a vinyl sulfonamide template.     

Energy transfer studies in binary dye solution mixtures: Acriflavine+Rhodamine 6G and Acriflavine+Rhodamine B

The effect of acceptor concentration on the energy transfer in Acriflavine (donar) plus Rhodamine 6G (Rh 6G) and Acriflavine plus Rhodamine B (Rh B) binary solution mixtures has been studied. The theoretical calculations are done to determine their lifetimes. Effect of these values on the total transfer efficiency at various acceptor concentrations have been studied to identify the appropriate energy transfer mechanism responsible for photon emissions, enhancement in lasing efficiency and dreading of the tenability of such mixed solutions. The energy transfer rate constants and critical transfer radius (R(0)) are calculated using Stern-Volmer plots and concentration dependence of radiative and non-radiative transfer efficiencies have also been determined. The experimental results indicate that dominant mechanism responsible for the efficient energy transfer in the binary mixtures is of non-radiative kind and is due to long-range dipole-dipole interaction.     

A pH dependent transport and back transport of americium(III) through the cellulose triacetate composite polymer membrane of cyanex-301 and TBP: role of H-bonding interactions

Transport of Am(III) was studied through the composite polymer membrane of Cyanex-301 [bis(2,4,4-trimethylpentyl)dithiophosphinic acid] and tri-n-butylphosphate (TBP). Depending on the pH of the strip solution containing alpha-hydroxyisobutyric acid (AHIBA), the transport behaviour of Am(III) was changed significantly. After approximately 70% of the Am(III) transported to the strip side, interestingly, back transport of Am(III) was observed at a pH of 3.5. The back transport phenomenon was not so significant at pH 1 and 5.7. The back transport of Am(III) was attributed to the transport of AHIBA from strip to the feed side due to its interaction with TBP in the membrane and the attainment of Donnan equilibrium because of the presence of Na(+) in the feed as the driving ion. The experimental observations were rationalized using the hydrogen bonding interaction energies obtained through ab initio molecular orbital and DFT calculations.     

Increasing the Value of Hominy Feed as a Coproduct by Fermentation

Hominy feed is a low value ($83.7/metric ton) coproduct of the corn dry milling process that accounts for nearly 35% of the starting corn quantity. The average composition of hominy feed on a dry basis is 56.9% starch, 25.2% neutral detergent fiber, 11.1% protein, and 5.3% fat. Starch in hominy feed can be fermented to ethanol thus increasing its levels of protein and fat. The increase in protein and fat percentages may increase the market competitiveness and price of hominy feed. Hydrolysis and fermentation were performed on nine hominy feed samples collected from three corn dry milling plants in the USA. The original hominy feed samples and postfermentation solids were analyzed for starch, protein, fat, and fiber content. Compared to the original hominy feed, the percentage increase in protein, fat and fiber in postfermentation solids of nine samples ranged from 10.4 to 21.3, 6.78 to 10.6, and 12.6 to 28.7% (dry basis), respectively. Ethanol yields varied from 271.7 to 380.2 l/metric ton for the nine hominy feed samples. These results indicate that the value of hominy feed as an animal feedstock can potentially be increased with fermentation and can produce more profit per metric ton than currently being derived by its sale as a low protein feed ingredient.     

Normal mode partitioning of Langevin dynamics for biomolecules

We propose a novel normal mode multiple time stepping Langevin dynamics integrator called NML. The aim is to approximate the kinetics or thermodynamics of a biomolecule by a reduced model based on a normal mode decomposition of the dynamical space. Our basis set uses the eigenvectors of a mass reweighted Hessian matrix calculated with a biomolecular force field. This particular choice has the advantage of an ordering according to the eigenvalues, which have a physical meaning of being the square of the mode frequency. Low frequency eigenvalues correspond to more collective motions, whereas the highest frequency eigenvalues are the limiting factor for the stability of the integrator. In NML, the higher frequency modes are overdamped and relaxed near their energy minimum while respecting the subspace of low frequency dynamical modes. Our numerical results confirm that both sampling and rates are conserved for an implicitly solvated alanine dipeptide model, with only 30% of the modes propagated, when compared to the full model. For implicitly solvated systems, NML gives a twofold improvement in efficiency over plain Langevin dynamics for sampling a small 22 atom (alanine dipeptide) model and in excess of an order of magnitude for sampling an 882 atom (bovine pancreatic trypsin inhibitor) model, with good scaling with system size subject to the number of modes propagated. NML has been implemented in the open source software PROTOMOL.