Structural modifications of aqueous ionic micelles in the presence of denaturants as studied by DLS and viscometry

Hydrophobic interactions control the morphologies of both surfactant aggregates and proteins. Globular proteins "denature" upon addition of excess amounts of denaturants such as urea. Understanding the microscopic basis of the urea effect on proteins or supramolecular aggregates such as micelles has always been a debated issue. Inspired by this need, the effect of urea (U), thiourea (TU), monomethylurea (MMU), dimethylurea(DMU), tetramethylurea (TMU), dimethylthiourea (DMTU), and tetramethylthiourea (TMTU) on the structural transition (spherical micelles to rod-shaped micelles, s --> r) in the sodium dodecylbenzenesulfonate (SDBS)-1-pentanol system has been investigated through dynamic light scattering(DLS) and viscosity measurements at 25 degrees C. 1-Pentanol, at 0.14 M, is found to promote s --> r in this system (0.2 M SDBS). The presence of the additives causes, in almost all cases, a decrease and increase in this 1-pentanol concentration depending upon the concentration and nature of the additive. These effects are explained in terms of an increased dielectric constant of the solvent medium due to the presence of additives and increased micellar hydration due to the repulsion of charged monomers caused by adsorption of the additives. Taken together, the data signal the exposure of biological assemblies to water at higher [additive], which causes a decrease in hydrophobic interactions responsible for compact structure formation (i.e., native protein).     

Gold nanoparticle networks with photoresponsive interparticle spacings

Photoresponsive gold nanoparticle networks were prepared by functionalizing them with azobenzene derivatives. A network can be formed when a linker molecule constituting the azobenzene moiety suitably derivatized on either side with gold surface sensitive groups such as thiols and amines is added to the nanoparticle solution. It is shown that the interparticle spacing in the networks could be controlled by the reversible trans-cis isomerization of the azobenzene moiety induced by UV and visible light, respectively. The photoinduced variation in the interparticle spacings is inferred by the changes in the optical spectra of the gold nanoparticles which display a red or blue shift in the surface plasmon resonance peak depending on a decrease or increase in the interparticle spacing, respectively. Transmission electron microscopy images are in consonance with the evidence from the optical spectra.     

An innovative synthesis of dibenzofurans through a carbanion-induced ring transformation reaction

An innovative route for the synthesis of substituted dibenzofurans has been delineated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 7-methoxybenzofuran-3-one, in high yield. The novelty of the procedure lies in the creation of an aromatic ring from a 2H-pyran-2-one involving the -COCH₂-moiety of the substrate.     

Catalytic hydrolysis of phosphodiesters by nucleophilic ions in gemini micellar media

The catalytic hydrolysis of bis(4‐nitrophenyl)phosphate (BNPP) and bis(2,4‐dinitrophenyl)phosphate (BDNPP) catalyzed by α‐nucleophiles in gemini micellar media was investigated at 27 °C. The cationic gemini surfactants, i.e., alkanediyl‐α‐ω‐bis(hydroxyethylmethylhexadecylammonium bromide) (16‐s‐16 MEA 2Br^?, where s = 4 and 6) were used. Nucleophilic reactivity of α‐nucleophiles such as hydroperoxide (HOO^?), acetohydroxamate (AHA^?), and butane 2,3‐dione monoximate ions (BDMO^?) were compared. The kinetic rate data were treated by applying the pseudophase model. The cationic gemini surfactants show unusual rate acceleration toward the cleavage of phosphodiesters with nucleophiles. These studies reveal that the hydroperoxide ion shows the highest catalytic activity reported so far with an unprecedented acceleration rate, 10⁷ times faster than that of the uncatalyzed reaction. The possible mechanism for the BNPP and BDNPP cleavage promoted by α‐nucleophiles is proposed on the basis of kinetic analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Measurements of atmospheric electrical conductivities during the total solar eclipse of 22 July, 2009

The effect of total solar eclipse on atmospheric conductivities has been studied. Continuous measurements of both types of positive and negative electrical conductivities and some meteorological parameters in conjunction with the total solar eclipse of 22 July, 2009 were made from 21 to 23 July, 2009 at Roorkee (29°52′ N, 77°53′ E, 275 m above sea level). Roorkee observed 90% maximum obscurity of eclipse since it was close to the path of totality. The event started from 05:28 AM IST and ended at 07:42 AM IST with the total eclipse at 06:30 AM IST. Considerable increase of both positive and negative conductivities were recorded during the eclipse with respect to those made on any other day. Increase in relative humidity and decrease in temperature were also observed during the period of eclipse.     

Synthesis,Characterization and Catalytic Behaviour of Silica Supported Zinc Salicylaldimine Complex

Zinc salicylaldimine complex immobilized on silica gel was used as a promising catalyst for the transesterification reaction of dimethyl terephthalate (DMT) and ethylene glycol (EG).The catalyst was characterized by Fourier transform infra‐red spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS). The product bis‐(2‐hydroxyethyl)terephthalate (BHET)was confirmed by mass and ¹H‐NMR studies. In comparison to zinc acetate i.e., homogeneous catalyst, a polymer supported catalyst showed better stability, catalytic activity and ease of separation from the reaction product. The catalyst can be reutilized during successive catalytic cycles.     

Quasi Monte Carlo-based isotropic distribution of gradient directions for improved reconstruction quality of 3D EPR imaging

In continuous wave (CW) electron paramagnetic resonance imaging (EPRI), high quality of reconstructed image along with fast and reliable data acquisition is highly desirable for many biological applications. An accurate representation of uniform distribution of projection data is necessary to ensure high reconstruction quality. The current techniques for data acquisition suffer from nonuniformities or local anisotropies in the distribution of projection data and present a poor approximation of a true uniform and isotropic distribution. In this work, we have implemented a technique based on Quasi-Monte Carlo method to acquire projections with more uniform and isotropic distribution of data over a 3D acquisition space. The proposed technique exhibits improvements in the reconstruction quality in terms of both mean-square-error and visual judgment. The effectiveness of the suggested technique is demonstrated using computer simulations and 3D EPRI experiments. The technique is robust and exhibits consistent performance for different object configurations and orientations.     

Dilute Ammonia Pretreatment of Sorghum and Its Effectiveness on Enzyme Hydrolysis and Ethanol Fermentation

A new pretreatment technology using dilute ammonium hydroxide was evaluated for ethanol production on sorghum. Sorghum fibers, ammonia, and water at a ratio of 1:0.14:8 were heated to 160 °C and held for 1 h under 140–160 psi pressure. Approximately, 44% lignin and 35% hemicellulose were removed during the process. Hydrolysis of untreated and dilute ammonia pretreated fibers was carried out at 10% dry solids at an enzyme concentration of 60 FPU Spezyme CP and 64 CBU Novozyme 188/g glucan. Cellulose digestibility was higher (84%) for ammonia pretreated sorghum as compared to untreated sorghum (38%). Fermentations with Saccharomyces cerevisiae D₅A resulted in 24 g ethanol /100 g dry biomass for dilute ammonia pretreated sorghum and 9 g ethanol /100 g dry biomass for untreated sorghum.