Monodisperse binary nanocomposite in silica with enhanced magnetization for magnetic separation

The majority of research on magnetic nanoparticles has focused on optical, electrical, and magnetic storage areas. Recently, the application of magnetic nanoparticles as magnetically separable nanovehicles for chemical or biological species has become an area of intensive research but with rather different challenging criteria that are yet to be addressed. For example, the enhancement of intrinsically weak magnetic properties, avoidance of magnetic interactions among particles, and improvement of the stability of the nanoparticles remain key issues. Here, it is demonstrated using sequential nanochemistry preparation techniques that exchange-coupled nanomagnets, such as FePt-Fe3Pt or FePt-Fe3O4 with dramatically enhanced magnetization, can be placed inside a silica nanosphere. The advantages of enhanced magnetization and the provision of protective coating and anchored sites on the silica shell surface render these new coated particles suitable for use in magnetic separation.

Effects of lactoperoxidase and hydrogen peroxide on rheological properties of yoghurt

The effects of activation of the lactoperoxidase (LPO) system by H2O2-NaSCN and hydrogen peroxide (H2O2) on the accessibility of sulphydryl groups (SH) in skimmed milk, and on the dynamic rheological properties of the resulting yoghurt were investigated. Four different concentrations of each reagent (20-80 mg H2O2-NaSCN/kg milk and 100-400 mg H2O2/kg milk) were compared. Clear negative correlations were noted between the accessibility of SH groups and both LPO activation rate and H2O2 concentration. Also the native PAGE pattern of the heat-treated samples showed that with increase in the H2O2-NaSCN and H2O2 concentrations, the level of interaction between beta-lactoglobulin (beta-Ig) and kappa-casein (K-CN) decreased. The complex modulus (G*) of skimmed milk yoghurts declined gradually with the decrease in the concentration of accessible SH groups accordingly. Tan delta values of yoghurt samples were found to be different from the control, but close to each other, indicating that protein interaction forces taking place in the formation of gel networks of treated yoghurts were different from the control.

Selective separation of the major whey proteins using ion exchange membranes

Synthetic microporous membranes with functional groups covalently attached were used to selectively separate beta-lactoglobulin, BSA, and alpha-lactalbumin from rennet whey. The selectivity and membrane performance of strong (quaternary ammonium) and weak (diethylamine) ion-exchange membranes were studied using breakthrough curves, measurement of binding capacity, and protein composition of the elution fraction to determine the binding behavior of each membrane. When the weak and strong anion exchange membranes were saturated with whey, they were both selective primarily for beta-lactoglobulin with less than 1% of the eluate consisting of alpha-lactalbumin or BSA. The binding capacity of a pure alpha-lactoglobulin solution was in excess of 1.5 mg/cm(2) of membrane. This binding capacity was reduced to approximately 1.2 mg/cm(2) when using a rennet whey solution (pH 6.4). This reduction in protein binding capacity can be explained by both the competitive effects of other whey proteins and the effect of ions present in whey. Using binary solution breakthrough curves and rennet whey breakthrough curves, it was shown that alpha-lactalbumin and BSA were displaced from the strong and weak anion exchange membranes by beta-lactoglobulin. Finally, the effect of ionic strength on the binding capacity of individual proteins for each membrane was determined by comparing model protein solutions in milk permeate (pH 6.4) and a 10 mM sodium phosphate buffer (pH 6.4). Binding capacities of beta-lactoglobulin, alpha-lactalbumin, and BSA in milk permeate were reduced by as much as 50%. This reduction in capacity coupled with the low binding capacity of current ion exchange membranes are 2 serious considerations for selectively separating complex and concentrated protein solutions.

An insight into the mechanism of protein separation by colloidal gas aphrons (CGA) generated from ionic surfactants

Colloidal gas aphrons (CGA), which are surfactant stabilised microbubbles, have been previously applied for the recovery of proteins from model mixtures and a few studies have demonstrated the potential of these dispersions for the selective recovery of proteins from complex mixtures. However there is a lack of understanding of the mechanism of separation and forces governing the selectivity of the separation. In this paper a mechanistic study is carried out to determine the main factors and forces influencing the selectivity of separation of whey proteins with CGA generated from ionic surfactants. Two different separation strategies were followed: (i) separation of lactoferrin and lactoperoxidase by anionic CGA generated from a solution of sodium bis-(2-ethyl hexyl) sulfosuccinate (AOT); (ii) separation of beta-lactoglobulin by cationic CGA generated from a solution of cetyltrimethylammonium bromide (CTAB). Separation results indicate that electrostatic interactions are the main forces determining the selectivity however these could not completely explain the selectivities obtained following both strategies. Protein-surfactant interactions were studied by measuring the zeta potential changes on individual proteins upon addition of surfactant and at varying pH. Interestingly strongest electrostatic interactions were measured at those pH and surfactant to protein mass ratios which were optimum for protein separation. Effect of surfactant on protein conformation was determined by measuring the change in fluorescence intensity upon addition of surfactant at varying pH. Differences in the fluorescence patterns were detected among proteins which were correlated to differences in their conformational features which could in turn explain their different separation behaviour. The effect of conformation on selectivity was further proven by experiments in which conformational changes were induced by pre-treatment of whey (heating) and by storage at 4 degrees C. Overall it can be concluded that separation of proteins by ionic CGA is driven mainly by electrostatic interactions however conformational features will finally determine the selectivity of the separation with competitive adsorption having also an effect. (c) 2006 Elsevier B.V. All rights reserved.

Selective separation of beta-lactoglobulin from sweet whey using CGAs generated from the cationic surfactant CTAB

The selective separation of whey proteins was studied using colloidal gas aphrons generated from the cationic surfactant cetyl trimethyl ammonium bromide (CTAB). From the titration curves obtained by zeta potential measurements of individual whey proteins, it was expected to selectively adsorb the major whey proteins, i.e., bovine serum albumin, alpha-lactalbumin, and beta-lactoglobulin to the aphrons and elute the remaining proteins (lactoferrin and lactoperoxidase) in the liquid phase. A number of process parameters including pH, ionic strength, and mass ratio of surfactant to protein (M-CTAB/M-TP) were varied in order to evaluate their effect on protein separation. Under optimum conditions (2 mmol/l CTAB, M-CTAB/M-TP = 0.26-0.35, pH 8, and ionic strength = 0.018 mol/l), 80-90% beta-lactoglobulin was removed from the liquid phase as a precipitate, while about 75% lactoferrin and lactoperoxidase, 80% bovine serum albumin, 95% immunoglobulin, and 65% alpha-lactalbumin were recovered in the liquid fraction. Mechanistic studies using zeta potential measurements and fluorescence spectroscopy proved that electrostatic interactions modulate only partially the selectivity of protein separation, as proteins with similar surface charges do not separate to the same extent between the two phases. The selectivity of recovery of beta-lactoglobulin probably occurs in two steps: the first being the selective interaction of the protein with opposite-charged surfactant molecules by means of electrostatic interactions, which leads to denaturation of the protein and subsequent formation and precipitation of the CTAB-beta-lactoglobulin complex. This is followed by the separation of CTAB-beta-lactoglobulin aggregates from the bulk liquid by flotation in the aphron phase. In this way, CGAs act as carriers which facilitate the removal of protein precipitate. (c) 2005 Wiley Periodicals, Inc.

Three-centre hydrogen bonds in triphenylphosphine oxide-hydroquinone (1/1)

The title cocrystal, C18H15OP center dot C6H6O2, belongs to a series of molecular systems based on triphenylphosphine P-oxide. The O atom of the oxide group acts as an acceptor for hydrogen bonds from OH groups of two hydroquinone molecules which lie on inversion centres [O center dot center dot center dot O = 2.7451 (17) and 2.681 (2) A S]. The crystal structure is stabilized by weak C-H center dot center dot center dot O hydrogen bonds, forming a C-2(1)(8) chain which runs parallel to the [100] direction.

Interpolymer complexes of hydroxy-propylmethylcellulose with polycarboxylic acids in aqueous solutions

The interactions between hydroxypropylmethylcellulose (HPMC) and poly(acrylic acid) (PAA) as well as poly(methacrylic acid) (PMMA) resulting in formation of hydrophobic interpolymer complexes (IPC) via hydrogen bonding have been studied in aqueous solutions in acidic medium. The formation of IPC of two different compositions (2:1 and 4:1) has been detected for complexes of PAA and HPMC. The critical pH values for complexation of HPMC with PAA and PMAA were determined by the turbidimetric method. It was found that PAA shows the lower complexation ability compared to PMAA due to the more hydrophobic nature of the latter polyacid. The temperature-induced phase separation in HPMC-PAA solution mixtures depends greatly on the components ratio and PAA molecular weight. The complexation ability of hydroxypropylmethylcellulose with respect to poly(acrylic acid) was found to be similar to the complexation ability of methylcellulose, lower than that of hydroxypropylcellulose and higher than that of hydroxyethylcellulose. (c) 2006 Society of Chemical Industry.

Hydrogen-bonded interpolymer complexes as materials for pharmaceutical applications

Association of poly(carboxylic acids) and non-ionic polymers in solutions via hydrogen bonding results in formation of novel polymeric materials-interpolymer complexes. These materials can potentially be used for design of novel mucoadhesive dosage forms, development of solid drug dispersions and solubilisation of poorly soluble drugs, encapsulation technologies, preparation of nanoparticles, hydrogels, in situ gelling systems and electrically erodible materials. This review is an attempt to analyse and systematise existing literature on pharmaceutical application of hydrogen-bonded interpolymer complexes. (c) 2007 Elsevier B.V All rights reserved.

Characterisation of blends based on hydroxyethylcellulose and maleic acid-alt-methyl vinyl ether

Hydrophilic polymeric films based on blends of hydroxyethylcellulose and maleic acid-co-methyl vinyl ether were produced by casting from aqueous solutions. The physicochemical properties of the blends have been assessed using Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, dielectric spectroscopy, etc. The pristine films exhibit complete miscibility due to the formation of intermacromolecular hydrogen bonding. The thermal treatment of the blend films leads to cross-linking via intermacromolecular esterification and anhydride formation. The cross-linked materials are able to swell in water and their swelling degree can be easily controlled by temperature and thermal treatment time. The formation of the crosslinks is apparent in the dynamic properties of the blends as observed through the mechanical relaxation and dielectric relaxation spectra. The dielectric characteristics of the material are influenced by the effects of change in the local structure of the blend on the ionic conduction processes and the rate of dipolar relaxation. Separation of these processes is attempted using the dielectric modulus method. Significant deviations from a simple additive rule of mixing on the activation energy are observed consistent with hydrogen bonding and crosslinking of the matrix. This paper indicates a method for the creation of films with good mechanical and physical characteristics by exposing the blends to a relatively mild thermal treatment.

Case study: object and ground point separation on a river bank using airborne based LIDAR data

In the past decade, airborne based LIght Detection And Ranging (LIDAR) has been recognised by both the commercial and public sectors as a reliable and accurate source for land surveying in environmental, engineering and civil applications. Commonly, the first task to investigate LIDAR point clouds is to separate ground and object points. Skewness Balancing has been proven to be an efficient non-parametric unsupervised classification algorithm to address this challenge. Initially developed for moderate terrain, this algorithm needs to be adapted to handle sloped terrain. This paper addresses the difficulty of object and ground point separation in LIDAR data in hilly terrain. A case study on a diverse LIDAR data set in terms of data provider, resolution and LIDAR echo has been carried out. Several sites in urban and rural areas with man-made structure and vegetation in moderate and hilly terrain have been investigated and three categories have been identified. A deeper investigation on an urban scene with a river bank has been selected to extend the existing algorithm. The results show that an iterative use of Skewness Balancing is suitable for sloped terrain.

Quasi Monte Carlo approach with uniform separation for solving of the rendering equation, ICNAAM 2007

This paper is directed to the advanced parallel Quasi Monte Carlo (QMC) methods for realistic image synthesis. We propose and consider a new QMC approach for solving the rendering equation with uniform separation. First, we apply the symmetry property for uniform separation of the hemispherical integration domain into 24 equal sub-domains of solid angles, subtended by orthogonal spherical triangles with fixed vertices and computable parameters. Uniform separation allows to apply parallel sampling scheme for numerical integration. Finally, we apply the stratified QMC integration method for solving the rendering equation. The superiority our QMC approach is proved.

Oxidation of polycrystalline Ni studied by spectromicroscopy: Phase separation in the early stages of crystallite growth

Low-energy and photoemission electron microscopy enables the determination of facet planes of polycrystalline surfaces and the study of their chemical composition at the sub-m scale. Using these techniques the early oxidation stages of nickel were studied. After exposing the surface to 20 L of oxygen at 373 K a uniform layer of chemisorbed oxygen was found on all facets. After oxygen exposure at 473–673 K, small NiO crystallites are formed on all facets but not in the vicinity of all grain boundaries. The crystallites are separated by areas of bare Ni without significant oxygen coverage.