Enzymatic synthesis of oligosaccharides, alkyl and terpenyl glucosides, by recombinant Escherichia coli-expressed Pichia etchellsii β-glucosidase II

The biosynthetic activity of yeast Pichia etchellsii β-glucosidase II (BglII) expressed in recombinant Escherichia coli was utilized for synthesis of cellooligosaccharides, alkyl and terpene glucosides. Cellooligosaccharides with a degree of polymerization of 3 and greater were resolved by thin-layer chromatography (TLC) using an ethyl acetate: 1-propanol:2-propanol:water (8:5:1:1) solvent system followed by visualization with 0.2% naphthoresorcinol reagent. Using 2M cellobiose and 15 IU of partially purified BglII, 57 mmol/L of oligosaccharides (comprising mostly cellotriose and cellopentaose) was synthesized in 16 h. Similarly, alkyl glucosides with chain lengths from 6 to 10 carbons were synthesized and products extracted to near purity by ethylacetate extraction. The same extraction method was employed to separate, to near purity, various monoterpenyl (nerol, geraniol, citronellol) glucosides. A reliable and simple method for separation of cellooligosaccharides using a combination of Bio-Gel P-2 gel filtration and charcoal celite adsorption chromatography was developed. The cellooligosaccharides were separated to purity as confirmed by TLC. The enzyme was among the very few that could synthesize a wide variety of glycoconjugates.     

High-pressure adsorption capacity and structure of CO2 in carbon slit pores: theory and simulation

We present new simulation results for the packing of single-center and three-center models of carbon dioxide at high pressure in carbon slit pores. The former shows a series of packing transitions that are well described by our density functional theory model developed earlier. In contrast, these transitions are absent for the three-center model. Analysis of the simulation results shows that alternations of flat-lying molecules and rotated molecules can occur as the pore width is increased. The presence or absence of quadrupoles has negligible effect on these high-density structures.     

Study of hexane adsorption in nanoporous MCM-41 silica

We study here the adsorption of hexane on nanoporous MCM-41 silica at 303,313, and 323 K, for various pore diameters between 2.40 and 4.24 nm. Adsorption equilibria, measured thermogravimetrically, show that all the isotherms, that are somewhat akin to those of type V, exhibit remarkably sharp capillary adsorption phase transition steps and are reversible. The position of the phase transition step gradually shifts from low to high relative pressure with an increase in the temperature as well as the pore sizes. The isosteric heats of adsorption derived from the equilibrium information using the Clapeyron equation reveal a gradual decrease with increasing adsorbed amount because of the surface heterogeneity but approach a constant value near the phase transition. A decrease in the pore size results in an increase in the isosteric heat of adsorption because of the increased dispersion forces. A simple strategy, based on the Broekhoff and De Boer adsorption theory, successfully interprets the hexane adsorption isotherms for the different pore size MCM-41 samples. The parameters of an empirical expression, used to represent the potential of interaction between the adsorbate and adsorbent, are obtained by fitting the monolayer region prior to capillary condensation and the experimental phase transition simultaneously, for some pore sizes. Subsequently, the parameters are used to predict the adsorption isotherm on other pore size samples, which showed good agreement with experimental data.     

The effect of length of single‐walled carbon nanotubes (SWNTs) on electrical properties of conducting polymer–SWNT composites

DC conductivity of conjugated polymer‐single‐walled carbon nanotube (SWNT) composite films has been measured for different SWNT concentrations. The composite was prepared by dispersing SWNTs in the poly (3‐octylthiophene), P3OT matrix already dissolved in xylene. The conductivity of the composite films showed a rapid increase as the SWNT concentration increases beyond a certain value. This behavior is explained in terms of percolating paths provided by the SWNTs in the volume of polymer matrix. To investigate the effect of length of nanotubes on the percolation conductivity, different SWNT samples were employed with similar diameter but varying tube lengths. It was found that the conductivity of the composite films is strongly dominated by the length of the nanotubes. Lower percolation limit and high conductivity value of composite films is observed for longer nanotubes. Furthermore, the conductivity is observed to be dependent on the size of the host polymer molecule also. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 89–95, 2010     

Anthocyanin-rich black currant extract suppresses the growth of human hepatocellular carcinoma cells

Dietary antioxidants, such as anthocyanins, are helpful in the prevention and control of various diseases by counteracting the imbalance of oxidative and antioxidative factors in the living systems. Black currant (Ribes nigrum L., Grossulariaceae) is known to contain high amounts of anthocyanins (250 mg/100 g fresh fruit). Black currant fruits have been used in Asian and European traditional medicine for the treatment of a variety of diseases. Black currant extract has recently been found to be the second most effective amongst nine different berry extracts studied for their free radical scavenging activity. Constituents present in black currant juice have been found to exert a number of health-promoting effects, including immunomodulatory, antimicrobial and antiinflammatory actions, inhibition of low-density lipoprotein, and reduction of cardiovascular diseases. Although antioxidant and antiinflammatory effects of black currant juice could be of value in preventing and treating oxidative stress- and inflammation-driven cancers, no experimental evidence is available to now. The objective of the present study was to evaluate the potential antiproliferative effects of black currant fruit skin extract against HepG2 human liver cancer cells. The aqueous extract yielded an anthocyanin-rich fraction with cyanidin-3-O-rutinoside as one of the major anthocyanins. This fraction exhibited a potent cytotoxic effect on HepG2 cells and this effect was more pronounced than that of delphinidin and cyanidin, two major aglycones of anthocyanins present in black currant. Our results indicate, for the first time, that black currant skin containing an anthocyanin-rich fraction inhibits the proliferation of liver cancer cells, possibly due to additive as well as synergistic effects. This product could be useful in the prevention and treatment of human hepatocellular carcinoma.     

A heterogeneous model for gas transport in carbon molecular sieves

A dual resistance model with distribution of either barrier or pore diffusional activation energy is proposed in this work for gas transport in carbon molecular sieve (CMS) micropores. This is a novel approach in which the equilibrium is homogeneous, but the kinetics is heterogeneous. The model seems to provide a possible explanation for the concentration dependence of the thermodynamically corrected barrier and pore diffusion coefficients observed in previous studies from this laboratory on gas diffusion in CMS. The energy distribution is assumed to follow the gamma distribution function. It is shown that the energy distribution model can fully capture the behavior described by the empirical model established in earlier studies to account for the concentration dependence of thermodynamically corrected barrier and pore diffusion coefficients. A methodology is proposed for extracting energy distribution parameters, and it is further shown that the extracted energy distribution parameters can effectively predict integral uptake and column breakthrough profiles over a wide range of operating pressures.     

Ionic conductivity enhancement of PVA: carboxymethyl cellulose poly-blend electrolyte films through the doping of NaI salt

Cellulose - In this paper, we report the effect of doping sodium iodide (NaI) salt into a polymer blend matrix of sodium carboxymethyl cellulose (NaCMC) and poly(vinyl alcohol) (PVA). Solution...     

Higher order duality in multiobjective fractional programming with support functions

In this paper a new class of higher order (F,ρ,σ)-type I functions for a multiobjective programming problem is introduced, which subsumes several known studied classes. Higher order Mond-Weir and Schaible type dual programs are formulated for a nondifferentiable multiobjective fractional programming problem where the objective functions and the constraints contain support functions of compact convex sets in Rn. Weak and strong duality results are studied in both the cases assuming the involved functions to be higher order (F,ρ,σ)-type I. A number of previously studied problems appear as special cases.