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Adsorption Model (adsorption + model)
Selected AbstractsA Random Sequential Adsorption Model for Protein Adsorption to Surfaces Functionalized with Poly(ethylene oxide)ADVANCED MATERIALS, Issue 16 2009Parag Katira A random sequential adsorption model for the adsorption of proteins to surfaces functionalized with poly(ethylene oxide)/poly(ethylene glycol) at a range of molecular weights and grafting densities is presented. An excellent fit of the model predictions to experimental results suggests that the random arrangement of polymer chains leading to polymer-free "bald" spots is a critical factor in primary protein adsorption. [source] Surface-enhanced Raman scattering study of the adsorption of the anthraquinone pigment alizarin on Ag nanoparticlesJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2004M. V. Cañamares Abstract FT-Raman and surface-enhanced Raman scattering (SERS) spectroscopy were applied in the vibrational characterization and study of the adsorption and acidity behavior of the highly fluorescent anthraquinone dye alizarin on Ag colloids prepared by chemical reduction with hydroxylamine hydrochloride. The SERS spectra were obtained at different conditions of pH, excitation wavelength and pigment concentration in order to deduce the adsorption mechanism of this molecule. On the basis of the results found we propose an adsorption model for alizarin, which has a different acidic behavior on the metal surface to that in solution. On the metal the deprotonation order of the OH groups changes with respect to the aqueous solution, the OH in position 1 being the first to be ionized instead of that in position 2 as occurs in solution. The two main alizarin forms identified on the metal surface correspond to the mono- and dianionic alizarin species. Copyright © 2004 John Wiley & Sons, Ltd. [source] Investigation of the mechanism of lubrication in starch,oil composite dry film lubricants,LUBRICATION SCIENCE, Issue 1 2007G. Biresaw Abstract The boundary coefficient of friction (COF) of starch,oil composite dry film lubricants was investigated as a function of starch type (waxy vs. normal purified food grade corn starch), oil chemistry (hexadecane vs. oleic acid and various vegetable oils), and starch-to-oil ratio. Based on the results, a mechanism of starch,oil interaction in these composites was proposed. According to the proposed mechanism: (a) the oil in the composite is distributed between the bulk and the surface of the starch; and (b) the fraction of the oil trapped in the bulk and that adsorbed on the surface are related to each other by an equilibrium constant, and are functions of the total oil concentration in the composite. In line with the proposed mechanism, an adsorption model was used to quantify the free energy of adsorption (,Gads) of the polar oils onto the starch surface. The analysis gave ,Gads values that were higher than those reported for the adsorption of the same polar oils onto steel surfaces. This result is consistent with the effect of the relative surface energies of steel and starch on the adsorption of polar oils. The adsorption property of the non-polar hexadecane relative to the polar oils was estimated by comparing their interfacial tensions with starch. The result showed a higher interfacial tension for hexadecane,starch than that for the polar oil,starch composites. This result predicts a relatively poorer compatibility with, and, hence, poorer adsorption of hexadecane onto starch leading to higher COF, as was observed in the friction measurements. Published in 2006 by John Wiley & Sons, Ltd. [source] Dye-affinity hollow-fibres and their lysozyme adsorption,desorption characteristicsPOLYMER INTERNATIONAL, Issue 10 2001Serap, enel Abstract Dye-affinity adsorption is increasingly used for protein separation. Hollow-fibres have advantages as adsorbents in comparison to conventional bead supports because they are not compressible and can eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyamide hollow-fibres to which Reactive Green HE-4BD was attached for adsorption of lysozyme. The hollow-fibre was characterized by scanning electron microscopy. These dye-carrying hollow-fibres (26.3,µmol,g,1) were used in the lysozyme adsorption,elution studies. The effect of initial concentration of lysozyme and medium pH on the adsorption efficiency of dye-attached hollow-fibres was studied in a batch system. The non-specific adsorption of lysozyme on the polyamide hollow-fibres was 1.8,mg,g,1. Reactive Green HE-4BD attachment significantly increased the lysozyme adsorption up to 41.1,mg,g,1. Langmuir adsorption model was found to be applicable in interpreting lead adsorption by Reactive Green HE-4BD attached hollow fibres. Significant amount of the adsorbed lysozyme (up to 95%) was eluted in 1,h in the elution medium containing 1.0,M NaSCN at pH 8.0. In order to determine the effects of adsorption conditions on possible conformational changes of lysozyme structure, fluorescence spectrophotometry was employed. We concluded that polyamide dye-affinity hollow-fibres can be applied for lysozyme adsorption without causing any significant conformational changes. Repeated adsorption,elution processes showed that these dye-attached hollow-fibres are suitable for lysozyme adsorption. © 2001 Society of Chemical Industry [source] Kinetic modeling of cellulosic biomass to ethanol via simultaneous saccharification and fermentation: Part I. Accommodation of intermittent feeding and analysis of staged reactorsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Xiongjun Shao Abstract The model of South et al. [South et al. (1995) Enzyme Microb Technol 17(9): 797,803] for simultaneous saccharification of fermentation of cellulosic biomass is extended and modified to accommodate intermittent feeding of substrate and enzyme, cascade reactor configurations, and to be more computationally efficient. A dynamic enzyme adsorption model is found to be much more computationally efficient than the equilibrium model used previously, thus increasing the feasibility of incorporating the kinetic model in a computational fluid dynamic framework in the future. For continuous or discretely fed reactors, it is necessary to use particle conversion in conversion-dependent hydrolysis rate laws rather than reactor conversion. Whereas reactor conversion decreases due to both reaction and exit of particles from the reactor, particle conversion decreases due to reaction only. Using the modified models, it is predicted that cellulose conversion increases with decreasing feeding frequency (feedings per residence time, f). A computationally efficient strategy for modeling cascade reactors involving a modified rate constant is shown to give equivalent results relative to an exhaustive approach considering the distribution of particles in each successive fermenter. Biotechnol. Bioeng. 2009;102: 59,65. © 2008 Wiley Periodicals, Inc. [source] Affinity Purification of Lipid VesiclesBIOTECHNOLOGY PROGRESS, Issue 1 2004Boris Peker We present a novel column chromatography technique for recovery and purification of lipid vesicles, which can be extended to other macromolecular assemblies. This technique is based on reversible binding of biotinylated lipids to monomeric avidin. Unlike the very strong binding of biotin and biotin-functionalized molecules to streptavidin, the interaction between biotin-functionalized molecules and monomeric avidin can be disrupted effectively by ligand competition from free biotin. In this work, biotin-functionalized lipids (biotin-PEG-PE) were incorporated into synthetic lipid vesicles (DOPC), resulting in unilamellar biotinylated lipid vesicles. The vesicles were bound to immobilized monomeric avidin, washed extensively with buffer, and eluted with a buffer supplemented with free biotin. Increasing the biotinyl lipid molar ratio beyond 0.53% of all lipids did not increase the efficiency of vesicle recovery. A simple adsorption model suggests 1.1 × 1013 active binding sites/mL of resin with an equilibrium binding constant of K = 1.0 × 108 M,1. We also show that this method is very robust and reproducible and can accommodate vesicles of varying sizes with diverse contents. This method can be scaled up to larger columns and/or high throughput analysis, such as a 96-well plate format. [source] Adsorption of 1,3-Benzenedithiol and 1,3-Benzenedimethanethiol on Gold Surfaces,CHEMPHYSCHEM, Issue 12 2008Jong Kuk Lim Dr. Abstract The adsorption characteristics of 1,3-benzenedithiol (1,3-BDT) and 1,3-benzenedimethanethiol (1,3-BDMT) on Au surfaces are investigated by means of surface-enhanced Raman scattering, UV/Vis absorption spectroscopy, and cyclic voltammetry (CV). 1,3-BDMT is found to adsorb via two S,Au linkages at concentrations below monolayer coverage, but to have an upright geometry as the concentration increases on Au nanoparticles. On the other hand, 1,3-BDT is found to adsorb by forming two S,Au linkages, regardless of concentration, based on the disappearance of the ,(SH)free stretching band. Because of the absence of the methylene unit, 1,3-BDT appeares not to self-assemble efficiently on Au surfaces. The UV/Vis absorption spectroscopy and CV techniques are also applied to check the formation of self-assembled monolayers of 1,3-BDT and 1,3-BDMT on Au. Density functional theory calculations based on a simple adsorption model using an Au8 cluster are performed to better understand the nature of the adsorption characteristics of 1,3-BDT and 1,3-BDMT on Au surfaces. [source] | ||||||||||||||||