A comprehensive study of lysozyme adsorption using dual polarization interferometry and quartz crystal microbalance with dissipation.

Protein adsorption plays a crucial role in biomaterial surface science as it is directly linked to the biocompatibility of artificial biomaterial devices. Here, elucidation of protein adsorption mechanism is effected using dual polarization interferometry and a quartz crystal microbalance to characterize lysozyme layer properties on a silica surface at different coverage values. Lysozyme is observed to adsorb from sparse monolayer to multilayer coverage. At low coverage an irreversibly adsorbed layer is formed with slight deformation consistent with side-on orientation. At higher coverage values dynamic re-orientation effects are observed which lead to monolayer surface coverages of 2-3 ng/mm² corresponding to edge-on or/and end-on orientations. These monolayer thickness values ranged between 3 and 4.5 nm with a protein density value of 0.60 g/mL and with 50 wt% solvent mass. Further increase of coverage results formation of a multilayer structure. Using the hydration content and other physical layer properties a tentative model lysozyme adsorption is proposed.

A comprehensive study of lysozyme adsorption using dual polarization interferometry and quartz crystal microbalance with dissipation

Protein adsorption plays a crucial role in biomaterial surface science as it is directly linked to the biocompatibility of artificial biomaterial devices. Here, elucidation of protein adsorption mechanism is effected using dual polarization interferometry and a quartz crystal microbalance to characterize lysozyme layer properties on a silica surface at different coverage values. Lysozyme is observed to adsorb from sparse monolayer to multilayer coverage. At low coverage an irreversibly adsorbed layer is formed with slight deformation consistent with side-on orientation. At higher coverage values dynamic re-orientation effects are observed which lead to monolayer surface coverages of 2-3 ng/mm2 corresponding to edge-on or/and end-on orientations. These monolayer thickness values ranged between 3 and 4.5 nm with a protein density value of 0.60 g/mL and with 50 wt% solvent mass. Further increase of coverage results formation of a multilayer structure. Using the hydration content and other physical layer properties a tentative model lysozyme adsorption is proposed. © 2012 Elsevier Ltd.

Studies on the adsorption equilibrium and kinetics of pentachlorophenol on suspended particulate matter of Donghu Lake water

In this paper, the adsorption equilibrium and kinetic behaviors of pentachlorophenol (PCP) on suspended particulate matter (SPM) in Donghu Lake water were investigated. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and their constants were evaluated. The results indicated that the adsorption of PCP on Donghu Lake SPM followed the Freundlich isotherm. Furthermore, the first order Lagergren rate equation and the pseudo-second order rate equation were used to describe the kinetic behaviors of PCP adsorption on Donghu Lake SPM, the rate constants were determined, and the kinetic process of the adsorption of PCP on Donghu Lake SPM followed the second order kinetic model.

Hydrodynamics in an expanded bed of large size ion-exchange resin, and natural product adsorption

Successful applications of expanded bed adsorption (EBA) technology have been widely reported in the literature for protein purification. Little has been reported on the recovery of natural products and active components of Chinese herbal preparations using EBA technology. In this study, the hydrodynamic behavior in an expanded bed of cation resin, 001 x 7 Styrene-DVB, was investigated. Ephedrine hydrochloride (EH) was used as a model natural product to test the dynamic binding capacity (DBC) in the expanded bed. EBA of EH directly from a feedstock containing powdered herbs has also been investigated. These particles are different from commercially available expanded bed adsorbents by virtue of their large size (20S to 1030 gm). When the adsorbent bed is expanded to approximately 1.3 to 1.5 times its settled bed height, the axial liquid-phase dispersion coefficient was found to be of the order 10(-5) m(2) s(-1), which falls into the range 1.0 x 10(-6) to 1.0 X 10(-5) m(2) s(-1) observed previously in protein purification. Because of the favorable column efficiency (low axial dispersion coefficient), the recovery yield and purification factor values of EH directly from a feedstock reached 86.5% and 18, respectively. The results suggest that EBA technology holds promise for the recovery of natural products and active components of Chinese herbal preparations.

Microfabries of lacustrine sediments to pollutant adsorption from a polluted Eutrophic lake, the Yangtze delta region

Two types of microfabrics relating to pollutant adsorption were studied in the scanning electronic microscope (SEM) in a polluted, eutrophic lake, the Yangtze delta region. Agglutinational texture or the aggregates of small particles are composed of clay minerals and fine organic fragments among the silty grains and the coatings with a thickness about 1 mu m were on the surfaces of the silty grains in the sediments. The chemical constituents of the aggregates and the coatings are K, Na, Ca, Mg, Si, Al, O, Fe, Ti, C, N and P determined in X-ray energy spectrometry connected with the SEM. In some cases, Pb was detected in the aggregates in the top sediment. It is suggested that nutrients and metals are adsorbed to the aggregates, which were formed by electrostatic attraction of physicochemical floes. The coatings on the surface of quartz grains were formed by the interaction of dissociated Al, Si, Fe, etc from silicates with dissolved N, P and C nutrients in interstitial water, which was aroused by human pollution to the lake in recent two decades.

Analysis of steric mass-action model for protein adsorption equilibrium onto porous anion-exchange adsorbent

The ion-exchange equilibrium of bovine serum albumin (BSA) to an anion exchanger, DEAE Spherodex M, has been studied by batch adsorption experiments at pH values ranging from 5.26 to 7.6 and ionic strengths from 10 to 117.1 mmol/l. Using the unadjustable adsorption equilibrium parameters obtained from batch experiments, the applicability of the steric mass-action (SMA) model was analyzed for describing protein ion-exchange equilibrium in different buffer systems. The parametric sensitivity analysis was performed by perturbing each of the model parameters, while holding the rest constant. The simulation results showed that, at high salt concentrations or low pHs close to the isoelectric point of the protein, the precision of the model prediction decreased. Parametric sensitivity analysis showed that the characteristic charge and protein steric factor had the largest effects on ion-exchange equilibrium, while the effect of equilibrium constant was about 70%-95% smaller than those of characteristic charge and steric factor under all conditions investigated. The SMA model with the relationship between the adjusted characteristic charge and the salt concentration can well predict the protein adsorption isotherms in a wide pH range from 5.84 to 7.6. It is considered that the SMA model could be further improved by taking into account the effect of salt concentration on the intermolecular interactions of proteins. (c) 2006 Elsevier Ltd. All rights reserved.

Effects of 9-cyanoanthracene and anthracene adsorption on the photoluminescence of porous silicon

The photoluminescence of porous silicon can be modified sensitively by surface adsorption of different kinds of molecules. A quite different effects of 9-cyanoanthracene and anthracene adsorption on the photoluminescence of porous silicon were observed. The adsorption of 9-cyanoanthracene induced the photoluminescence enhancement, while anthracene adsorption resulted in photoluminescent quenching. An explanation of the interaction of adsorbates with surface defect sites of porous silicon was suggested and discussed. (C) 1998 Elsevier Science S.A.

THE ADSORPTION OF O2 ON FESI SURFACES

The initial adsorption stages and the interaction of oxygen on FeSi surfaces have been studied as a function of exposure and annealing temperature using a variety of techniques including HREELS, AES, LEED, XPS and UPS. O2 was found to adsorb dissociatively on the FeSi surfaces at room temperature. The whole adsorption process can be divided into four stages. Heating promotes the oxidation of Si, and a thin SiO2 overlayer is formed on the surface when annealed at 450-degrees-C, while all FeOx species are reduced. Models for adsorbed atomic O on the FeSi(100) surface exposed to different oxygen exposures have been put forward to account for the observed experimental results.