Surface properties of Reactive Yellow 2 immobilised pHEMA and HEMA/chitosan membranes: characterisation of their selectivity to different proteins

Poly(hydroxyethyl methacrylate), pHEMA, and a composite pHEMA/chitosan networks were synthesized in the membrane form via UV initiated photo-polymerisation in the presence of an initiator ,′-azoisobutyronitrile. Reactive Yellow 2 (RY-2) was covalently immobilised as a dye–ligand onto both membranes. The polarity and surface energy of the investigated membranes were determined by contact angle measurement. The incorporation of chitosan in the pHEMA networks produced more hydrophilic surface, as indicated by contact angle analysis. The binding characteristics of lysozyme, γ-globulins, human serum albumin (HSA) and bovine serum albumin (BSA) to pHEMA-RY-2 and pHEMA/chitosan-RY-2 affinity membranes have been investigated from aqueous solution and their dye–ligand free forms were used as control systems. When chitosan was incorporated in the pHEMA network as a cationic polymer led to higher adsorption capacity for the lysozyme. Selective adsorption behaviour was also observed in the case of pHEMA/chitosan-RY-2 membrane for the lysozyme. The non-specific adsorptions of the lysozyme on the pHEMA and pHEMA/chitosan membranes were about 1.9 and 7.2 mg/ml, respectively. These were negligible for all others investigated proteins. The lysozyme adsorption data was analysed using the first-order and the second-order models. The first-order equation in both affinity membrane systems is the most appropriate equation to predict the adsorption capacities of the adsorbents. The adsorption isotherms well fitted the combined Langmuir–Freundlich model. A theoretical analysis has been conducted to estimate the thermodynamic contributions (changes in enthalpy, entropy and Gibbs free energy) for the adsorption of lysozyme to both dye–ligand immobilised membranes. The adsorption capacities of both dye–ligand immobilised membranes increased with increasing the temperature while decreased with increasing the NaCl concentration. Both affinity membranes are stable when subjected to sanitization with sodium hydroxide after repeated separation–elution cycles.     

Production of citric acid using immobilized conidia of Aspergillus niger

Conidia of Aspergillus niger were immobilized in calcium alginate gel for the production of citric acid. First, the type of the preactivation medium, together with the preactivation period, was investigated. It was found that A. niger requires a 2-d preactivation period at a 0.05 g/L NH₄NO₃ concentration. Second, preactivated cells were used to determine the effects of nitrogen concentration and the flow rate of oxygen and air on the production of citric acid. Maximum citric acid production was attained with medium containing 0.01 g/L of NH₄NO₃. The rate of citric acid production in the nitrogenous medium was 33% higher when oxygen was used instead of air during the production phase. This corresponds to an increase of 85% when compared to production when neither oxygen nor air was fed into the system. In the nonnitrogenous medium citric acid concentration remained similar regardless of the use of air or oxygen. However, in the nonnitrogenous production medium, citric acid production was not influenced considerably when oxygen was used instead of air. The advantage of using immobilized cells is that production is achieved easily in the continuous system. Therefore, citric acid production was also tested using a packed-bed bioreactor, and an increase in productivity by a factor of 22 was achieved compared to the batch system.     

Material profile influences in bulk‐heterojunctions

The morphology in mixed bulk‐heterojunction films are compared using three different quantitative measurement techniques. We compare the vertical composition changes using high‐angle annular dark‐field scanning transmission electron microscopy with electron tomography and neutron and x‐ray reflectometry. The three measurement techniques yield qualitatively comparable vertical concentration measurements. The presence of a metal cathode during thermal annealing is observed to alter the fullerene concentration throughout the thickness of the film for all measurements. However, the absolute vertical concentration of fullerene is quantitatively different for the three measurements. The origin of the quantitative measurement differences is discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1291–1300     

Thermal dry reforming of methane over La2O3 co-supported Ni/MgAl2O4 catalyst for hydrogen-rich syngas production

Research on Chemical Intermediates - The excess emission of greenhouse gases (GHGs) such as CO2 and CH4 is posing an acute threat to the environment, and efficient ways are being sought to utilize...     

The effect of variety seeking behaviour on optimal product positioning

In this paper we develop a stochastic (first order Markovian) consumer choice model that represents variety seeking behaviour and we investigate the practical implications of this model for optimal product positioning relative to a zero order model that does not incorporate variety seeking. We show that the optimal positioning implications of a variety seeking process is indeed different than those of a (no-variety-seeking) zero order process. Based on intuition, one might expect increased variety seeking to imply that firms should increase the distance between their products in an attribute space. In fact, we show that this effect does occur for relatively low share brands. But just the opposite effect holds for relatively high share brands. That is, variety seeking behaviour generates a desire to more differentiation among low share brands, and a desire for less differentiation among high share brands.     

Effect of reactive and nonreactive surface modifications and compatibilizer use on mechanical and flame-retardant properties of linear low-density polyethylene filled with huntite and hydromagnesite mineral

Journal of Thermal Analysis and Calorimetry - In the current study, huntite and hydromagnesite (HH) was used as flame-retardant additive in linear low-density polyethylene (LLDPE). The effect of HH...     

An electrochemical chiral sensor based on electrochemically modified electrode for the enantioselective discrimination of D-/L-tryptophan

Journal of Solid State Electrochemistry - Chirality is a universal characteristic of natural systems and discrimination of enantiomers of a chiral molecule plays a major role particularly in...