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Adsorption
Kinds of Adsorption Terms modified by Adsorption Selected AbstractsMUCILAGINOUS CAPSULE ADSORPTION AND INTRACELLULAR UPTAKE OF COPPER BY KIRCHNERIELLA APERTA (CHLOROCOCCALES)1JOURNAL OF PHYCOLOGY, Issue 2 2002Ana T. Lombardi The purpose of the present investigation was to evaluate possible ecological and physiological functions of mucilaginous capsules produced by the freshwater algae Kirchneriella aperta Teiling (Chlorococcales) as related to copper ions. All experiments were performed using synthetic media under laboratory-controlled conditions. Copper interactions were investigated by distinguishing between adsorption onto the mucilaginous material present at the surface of the cells, intracellular uptake, and differentiation between total dissolved copper and free copper ions in the culture medium. Kirchneriella aperta is sensitive to copper, as revealed by a 96-h EC50 value of 10,9.22 M Cu2+. We demonstrated that the mucilaginous capsules were able to sequester copper ions from the medium through a passive mechanism, thus providing the cell with a mechanism able to postpone the toxic effects of copper. The organic material that diffuses into the test medium as well as the mucilaginous capsules produced by K. aperta both effectively complex copper; thus, toxicity must be related to free copper ions and not the total dissolved copper concentration in the medium. [source] SURGICAL ADHESIONS: EVIDENCE FOR ADSORPTION OF SURFACTANT TO PERITONEAL MESOTHELIUMANZ JOURNAL OF SURGERY, Issue 6 2000Y. Chen Background: It has been speculated that the formation of surgical adhesions must be preceded by physical adhesion of the two surfaces, a process normally prevented by a lining of adsorbed surface-active phospholipid (surfactant) acting as both a superb boundary (solid-to-solid) lubricant and a release (antistick) agent. Animal trials administering exogenous surfactant as a dry powder (ALECÔ) have previously demonstrated a reduction of 80% in abdominal adhesions. Methods: Incubation of rat peritoneum (both live and excised) with radiolabelled dipalmitoyl phosphatidylcholine (DPPC) has been used to demonstrate adsorption; while the normal lining of surfactant in the human abdominal cavity has been confirmed by epifluorescence microscopy using Phosphin E as the hydrophobic probe. Aims: The overall aim is to confirm that peritoneal mesothelium has a lining of surfactant known for its lubricating and release properties, and that this lining can be enhanced by the adsorption of exogenous material. Results: Adsorption of DPPC to peritoneal mesothelium was 470 ng/cm 2 (n = 8) ex vivo and 598 ng/cm 2 (n = 18) in vivo, these rates being enhanced by EggPG by 62%ex vivo and 47%in vivo to reach the equivalent of almost three close-packed monolayers. Conclusions: These results can explain the reduction in surgical adhesions previously reported in animals by administering ALECÔ (7:3 DPPC:EggPG) as a highly surface-active dry powder, although it is now used in saline suspension to treat respiratory distress syndrome in newborns, in whom it has no side-effects. These findings would appear to justify clinical trials for dry ALECÔ in suppressing surgical adhesions with minimal risk of an adverse reaction. The results of these trials are also discussed and found to be compatible with the known ability of surfactant to resist physical adhesion by fibronectin, the tacky ,glue' by which fibroblasts attach to surfaces as the first step in formation of fibrinous adhesions. [source] A Contribution to the Study of the Adsorption of s -Triazine Herbicides on Glassy Carbon Electrodes by Differential-Capacity MeasurementsELECTROANALYSIS, Issue 6 2010S. Pintado Abstract Measurements of differential capacity vs. potential have been made for a series of s -triazine herbicides at different concentrations. In all cases the decrease in capacity was independent of the applied potential, so the adsorption is also independent of the potential. From the measurements it can be established that the adsorption follows Langmuir type isotherms. Adsorption constants were obtained for the different herbicides at 25,°C (simetryn, simazine, terburyn and prometon) as well as those to simetryn at different temperatures, from which the adsorption enthalpy of this herbicide was calculated being its value of 17.5,kJ mol,1. [source] Quantitative Studies of Metal Ion Adsorption on a Chemically Modified Carbon Surface: Adsorption of Cd(II) and Hg(II) on Glutathione Modified CarbonELECTROANALYSIS, Issue 8 2009Poobalasingam Abiman Abstract The adsorption behavior of model toxic metal cations namely Cd(II) and Hg(II) on carbon surfaces chemically modified by glutathione was investigated as a function of the concentration of Cd2+ and Hg2+ ions, time and the amount of modified carbon used. Square wave and linear sweep anodic stripping voltammetry was used to monitor the uptake of Cd(II) and Hg(II) ions respectively. Kinetic and adsorption isotherm studies reveal that both Cd(II) and Hg(II) ions undergo similar large adsorption with the modified glutathione carbon material (Glu-carbon). [source] Construction of L -Lysine Sensor by Layer-by-Layer Adsorption of L -Lysine 6-Dehydrogenase and Ferrocene-Labeled High Molecular Weight Coenzyme Derivative on Gold ElectrodeELECTROANALYSIS, Issue 24 2008Haitao Zheng Abstract A ferrocene-labeled high molecular weight coenzyme derivative (PEI-Fc-NAD) and a thermostable NAD-dependent L -lysine 6-dehydrogenase (LysDH) from thermophile Geobacillus stearothermophilus were used to fabricate a reagentless L -lysine sensor. Both LysDH and PEI-Fc-NAD were immobilized on the surface of a gold electrode by consecutive layer-by-layer adsorption (LBL) technique. By the simple LBL method, the reagentless L -lysine sensor, with co-immobilization of the mediator, coenzyme, and enzyme was obtained, which exhibited current response to L -lysine without the addition of native coenzyme to the analysis system. The amperometric response of the sensor was dependent on the applied potential, bilayer number of PEI-Fc-NAD/LysDH, and substrate concentration. A linear current response, proportional to L -lysine concentration in the range of 1,120,mM was observed. The response of the sensor to L -lysine was decreased by 30% from the original activity after one month storage. [source] Electrochemical Investigation of Binding of Heavy Metal Ions to Turkish LignitesELECTROANALYSIS, Issue 16 2004Erol Pehlivan Abstract Adsorption and desorption of Cu2+, Pb2+, Cd2+, Ni2+ and Zn2+ ions on samples of lignites (young brown coal) from three areas in the vicinity of Konya (Anatolia, Turkey) were followed using the polarographic method of analysis. This method enables the determination of free metal ions in suspensions containing both small and colloidal particles of lignite. Effects of pH, nature of the metal ion, and origin of the lignite on its adsorption capacity were followed. Binding is only between 5 and 30% reversible, indicating that ion exchange is not the predominant factor. The role of the size and shape of cavities inside pulverized lignite and of the functional groups inside these cavities was considered. [source] Study of the Complexation, Adsorption and Electrode Reaction Mechanisms of Chromium(VI) and (III) with DTPA Under Adsorptive Stripping Voltammetric ConditionsELECTROANALYSIS, Issue 19 2003Sylvia Sander Abstract The complexation of Cr(III) and Cr(VI) with diethylenetriaminepentaacetic acid (DTPA), the redox behavior of these complexes and their adsorption on the mercury electrode surface were investigated by a combination of electrochemical techniques and UV/vis spectroscopy. A homogenous two-step reaction was observed when mixing Cr(III), present as hexaquo complex, with DTPA. The first reaction product, the electroactive 1,:,1 complex, turns into an electroinactive form in the second step. The results indicate that the second reaction product is presumably a 1,:,2 Cr(III)/DTPA complex. The electroreduction of the DTPA-Cr(III) complex to Cr(II) was found to be diffusion rather than adsorption controlled. The Cr(III) ion, generated in-situ from Cr(VI) at the mercury electrode at about ,50,mV (vs. Ag|AgCl) (3,mol,L,1 KCl), was found to form instantly an electroactive and adsorbable complex with DTPA. By means of electrocapillary measurements its surface activity was shown to be 30 times higher than that of the complex built by homogenous reaction of DTPA with the hydrated Cr(III). Both components, DTPA and the in-situ built complex Cr(III) ion were found to adsorb on the mercury electrode. The effect of nitrate, used as catalytic oxidant in the voltammetric determination method, on the complexation reaction and on the adsorption processes was found to be negligible. The proposed complex structures and an overall reaction scheme are shown. [source] Integrated Enzymatic Synthesis and Adsorption of Isomaltose in a Multiphase Fluidized Bed ReactorENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2006M. Ergezinger Abstract Dextransucrase catalyzes the formation of dextran, but also of numerous oligosaccharides from sucrose and different acceptors, if appropriate conditions are chosen. A process on a technical scale with immobilized enzyme was established to produce isomaltose, a disaccharide of industrial interest. Isomaltose is also a reactant for dextransucrase and has to be quickly taken out of the reaction solution. This was realized by integrated adsorption of isomaltose on zeolites. In the case of biotransformation the reactor works with a fluidized bed of immobilized enzyme and the in situ separation is realized with a suspension flow of adsorbent. This process was investigated experimentally and theoretically. With a design model consisting of hydrodynamics, kinetics of enzymatic synthesis, and thermodynamics of adsorption, a comparison was made between experimental and calculated data. [source] Adsorption of hydrophobic organic compounds onto a hydrophobic carbonaceous geosorbent in the presence of surfactants,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2008Peng Wang Abstract The adsorption of hydrophobic organic compounds (HOCs; atrazine and diuron) onto lampblack was studied in the presence of nonionic, cationic, and anionic surfactants (Triton® X-100), benzalkonium chloride [BC], and linear alkylbenzene sulfonate [LAS]) to determine the effect of the surfactant on HOC adsorption onto a hydrophobic carbonaceous geosorbent. Linear alkylbenzene sulfonate showed an adsorption capacity higher than that of BC but similar to that of Triton X-100, implying the charge property of a surfactant is not a useful indicator for predicting the surfactant's adsorption onto a hydrophobic medium. The results also indicated that the octanol-water partition coefficient (Kow) of a surfactant is not a good predictor of that surfactant's sorption onto a hydrophobic medium. Under subsaturation adsorption conditions (i.e., before sorption saturation is reached), surfactant adsorption reduced HOC adsorption to a significant extent, with the reduction in HOC adsorption increasing monotonically with the amount of surfactant adsorbed. Among the three surfactants, Triton X-100 was the most effective in reducing HOC adsorption, whereas BC and LAS showed similar effectiveness in this regard. Under the same amount of the surfactant sorbed, the reduction in atrazine adsorption was consistently greater than that for diuron because of atrazine's lower hydrophobicity. No significant difference was observed in the amount of the HOC adsorbed under different adsorption sequences. Our results showed that the presence of surfactant can significantly decrease HOC adsorption onto hydrophobic environmental media and, thus, is important in predicting HOC fate and transport in the environment. [source] Accumulation of 137Cs by larvae of the midge Chironomus riparius from sediment: Effect of potassiumENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2003Lieven Bervoets Abstract We studied the effect of potassium on the uptake of radiocesium from sediment by larvae of the midge Chironomus riparius. Sediment ingestion rate was determined for one week. After 24 h the gut content remained constant, indicating that equilibrium was reached between sediment ingestion and sediment elimination. These data were used to account for radiocesium present in the gut in subsequent uptake experiments. Reference sediment was equilibrated with solutions containing different concentrations of potassium: 1, 10, 100, and 1,000 ,M. Adsorption of 137Cs to the sediment was investigated. Three different radiocesium levels (0.3, 0.6, and 1.2 KBq/ml) were applied at the four different potassium levels. In all cases more than 94% of all radiocesium was adsorbed to the sediment within 48 h. The sediment, equilibrated with the four different potassium levels, was spiked with a constant amount of 296 Bq/ml 137Cs. Accumulation by midge larvae was followed for one week, and subsequently elimination was followed for another week. No significant differences in radiocesium levels in midge larvae among the treatments were found after one week of exposure. However, using a one-compartment accumulation model, a small but significant effect of potassium in water and sediment on the uptake and elimination rate constants (ka and ke) was found. These results indicate that although differences were rather small, radiocesium accumulation decreased with increasing potassium level in the sediment. [source] Nitrogen Trifluoride as a Bifunctional Lewis Base: Implications for the Adsorption of NF3 on Solid SurfacesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2004Paola Antoniotti Abstract The structure, stability, and thermochemistry of isomeric adducts between NF3 and the Lewis acids BH3,nFn (n = 0,3) have been investigated at the coupled-cluster and at the Gaussian-3 (G3) level of theory. At the CCD/cc-pVDZ level both the nitrogen- and the fluorine-coordinated structures of all BH3,nFn,(NF3) (n = 0,3) adducts were characterized as true minima on the potential energy surface, thus providing the first theoretical evidence for the behavior of NF3 as a bifunctional Lewis base when interacting with neutral Lewis acids. At the G3 level, and 298.15 K, including the contribution of the entropy term, the H3B,NF3 adduct is predicted to be more stable than H3B,F,NF2 by 4.3 kcal mol,1; this free energy difference is 3.7 kcal mol,1 at the CCSD(T)/cc-pVTZ//CCD/cc-pVDZ level of theory. Conversely, at the latter computational level, the fluorine-coordinated isomers of the BH2F,(NF3), BHF2,(NF3), and BF3,(NF3) adducts are practically degenerate with the nitrogen-coordinated ones. BH3,nFn,(NF3) (n = 0,3) complexes feature typical bond dissociation energies of ca. 1,2 kcal mol,1, and are predicted to be thermodynamically stable only at low temperatures. However, the appreciable influence of the basis set superposition error (BSSE) prevents a quantitative assessment of these small computed dissociation energies. Finally, we briefly discuss the implications of our calculations for the adsorption of NF3 on solid surfaces. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Optimization of activated carbon-based decontamination of fish oil by response surface methodologyEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7 2007Åge Oterhals Abstract The effect of activated carbon (AC) adsorption on the reduction of persistent organic pollutants (POP) in fish oil was studied based on response surface methodology at a 5-g/kg AC inclusion level. Pretreatment of the oil by alkali refining and bleaching increased the POP levels. The tested process variables (contact time and temperature) affected the AC adsorption rate and significant first- and second-order response models could be established. Polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/F) showed a very rapid adsorption behavior and the concentration and toxic equivalent (TEQ) level could be reduced by 99%. Adsorption of dioxin-like polychlorinated biphenyls (DL-PCB) was less effective and depended on ortho substitution, i.e. non- ortho PCB were adsorbed more effectively than mono- ortho PCB with a maximum of 87 and 21% reduction, respectively, corresponding to a DL-PCB-TEQ reduction of 73%. A common optimum for both PCDD/F and DL-PCB adsorption could not be identified. AC treatment had no effect on the level of polybrominated diphenyl ether flame retardants. The differences in adsorption patterns may be explained based on molecular conformation. No change in oil quality could be observed based on oxidation parameters. Compliance with present PCDD/F and DL-PCB legislation levels in fish oil can be achieved based on AC adsorption. [source] Medical Potentialities of Biomimetic Apatites through Adsorption, Ionic Substitution, and Mineral/Organic Associations: Three Illustrative Examples,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Ahmed Al-Kattan Biomimetic calcium phosphate apatites are particularly adapted to bio-medical applications due to their biocompatibility and high surface reactivity. In this contribution we report three selected examples dealing with mineral/organic interactions devoted to convey new functionalities to apatite materials, either in the form of dry bioceramics or of aqueous colloids. We first studied the adsorption of risedronate (bisphosphonate) molecules, which present potential therapeutic properties for the treatment of osteoporosis. We then addressed the preparation of luminescent Eu-doped apatites for exploring apatite/collagen interfaces through the FRET technique, in view of preparing "advanced" biocomposites exhibiting close spatial interaction between apatite crystals and collagen fibers. Finally, we showed the possibility to obtain nanometer-scaled apatite-based colloids, with particle size tailorable in the range 30,100,nm by controlling the agglomeration state of apatite nanocrystals by way of surface functionalization with a phospholipid moiety. This paper is aimed at illustrating some of the numerous potentialities of calcium phosphate apatites in the bio-medical field, allowing one to foresee perspectives lying well beyond bone-related applications. [source] An X-ray Spectromicroscopy Study of Albumin Adsorption to Crosslinked Polyethylene Oxide Films,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Bonnie O. Leung Abstract Synchrotron-based X-ray photoemission electron microscopy (X-PEEM) is used to characterize the near surface composition of polyethylene oxide (PEO) combined with 1.5, 5, and 10,wt.-% pentaerythritol triacrylate (PETA) crosslinker. It is found that as the concentration of PETA increases, it becomes the dominant component in the top 10,nm of the film surface. The same surfaces are also exposed to human serum albumin (HSA) and the distributions of the protein relative to PEO and PETA measured with X-PEEM. A positive correlation is found between levels of PETA and HSA at the surface. Above PETA concentrations of 5,wt.-%, HSA adsorption is significant, which suggests high levels of PETA (often used to immobilize PEO by crosslinking) can significantly reduce the non-fouling properties of PEO. [source] Biphasic Resorbable Calcium Phosphate Ceramic for Bone Implants and Local Alendronate Delivery,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Shashwat S. Banerjee A novel biphasic calcium phosphate ceramic composed of tricalcium phosphate (TCP) and calcium pyrophosphate (CP) is synthesized in order to tailor the biodegradation behavior of the ceramic. The results show that biphasic TCP/CP ceramic has a strength of 62.2,±,2.1 MPa, which is superior to single-phase TCP and CP ceramics, which show strengths of 44.3,±,3.0 and 53.0,±,4.8 MPa, respectively. In addition, biphasic TCP/CP ceramic displays a controlled strength degradation from 62.2,±,2.1 to 40.5,±,1.0 MPa in stimulated body fluid over a period of 28 d. An in vitro cell materials interaction study using human fetal osteoblast cells indicates that TCP/CP ceramic is cytocompatible. TCP/CP ceramic also show a good loading capacity for alendronate. Adsorption of alendronate (AD) on the TCP/CP surface is found to proceed via ligand exchange mechanism and the in vitro release profile of AD from TCP/CP surface is characterized by an initial fast release followed by a slow and sustained release. Strong electrostatic interactions between AD groups and surface Ca2+ ions enable the slow and sustained release of AD. These results demonstrate that the newly developed biphasic ceramic, with its controlled strength degradation and drug release, shows promise for use in orthopedic and tissue engineering applications. [source] Surface Physiochemistry Affects Protein Adsorption to Stoichiometric and Silicate-Substituted Microporous Hydroxyapatites,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Katharina Guth An important factor in the bioactivity and success of a bone-graft substitute is the nature of the adsorbed protein layer, which plays a vital role in orchestrating cell attachment and development through the presence of adhesion proteins such as fibronectin (Fn) and vitronectin (Vn). In this study, microporous hydroxyapatite (HA) and silicate-substituted hydroxyapatite (SA) discs with matched porosity and surface morphology are developed to mimic the topography found in commercial bone-graft substitutes in order to identify whether the introduction of microporosity and associated surface roughness eliminates the beneficial effect that silicate substitution has on protein adsorption. The introduction of microporosity does not abolish the relative enrichment of the protein layer that is adsorbed to the microporous SA discs, as opposed to HA, but appears to accelerate it. Fibronectin and Vn adsorption in a range of competitive environments at physiological temperatures confirm that the microporous SA discs have a greater affinity for Fn and Vn compared with HA, suggesting differences in the mechanisms behind the surface affinity to SA. Thus, development of a surface protein layer on SA and HA is likely to be dependent on the nature of the local protein environment and a combination of factors that are associated with the addition of silicate: the surface charge, the nature of the ionic species at the interface and the resultant hydrophilicity of the surface. Total protein adsorption is not found to be a good indicator of potential implant performance, particularly at early time points. [source] Bovine Serum Albumin and Lysozyme Adsorption on Calcium Phosphate ParticlesADVANCED ENGINEERING MATERIALS, Issue 1-2 2010Berit Mueller Two model proteins that are oppositely charged at neutral pH , bovine serum albumin (BSA) and lysozyme, with acidic and alkaline isoelectric points, respectively , are used to investigate the protein adsorption behaviour of hydroxyapatite and beta-tricalcium phosphate (, -TCP) particles. Both calcium phosphate based particles are highly relevant for the fabrication of bioactive and resorbable bone implants. The investigations are carried out by combining zeta potential and Vis spectroscopy measurements. The changes of zeta potential and isoelectric point are determined as a function of added protein. Both proteins form a monolayer on , -TCP, while on hydroxyapatite only semi-monolayers were measured. For BSA, a side-on adsorption mode is suggested, whereas end-on adsorption appears to be most likely for lysozyme. The zeta potential curves as a function of adsorbed protein show that plateaus of the protein amounts adsorbed increase with charge saturation. In addition, the spatial charge distribution of both proteins is modelled to get a further understanding of the initial adsorption orientation of the biomolecules, supporting the findings from the experimental data. The reported findings can be transferred to the adsorption behaviour of a variety of proteins on calcium phosphate surfaces and are helpful for the fabrication of bone-analogous calcium phosphate/protein nanocomposites. [source] Adsorption of phthalic acid and salicylic acid by two variable charge soils as influenced by sulphate and phosphateEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2007R. K. Xu Summary Low-molecular-weight (LMW) organic acids exist widely in soils, especially in the rhizosphere, and the adsorption of these acids may affect their reactions in soils. The adsorption behaviour of phthalic acid and salicylic acid by two variable charge soils (a Rhodic Ferralsol and a Haplic Acrisol) was investigated. Both soils exhibited great adsorption capacity for these organic acids, with a greater affinity for phthalic acid. The Rhodic Ferralsol adsorbed more organic acids of both kinds than the Haplic Acrisol, which was consistent with the content of iron and aluminum oxides in the two soils. The iron oxides in these soils played a significant role in adsorption of the organic acids, whilst the soil aluminosilicate minerals, such as kaolinite, showed a small adsorption capacity. The presence of phosphate and sulphate caused a decrease in the adsorption of both organic acids because of their competition with them for sorption sites. The phosphate showed a bigger inhibition on the adsorption than sulphate as a result of a greater amount of phosphate adsorbed by the soils. The adsorption of both organic acids was affected by pH only slightly at pH < 4.5. However, the adsorption decreased with the increase in pH at pH > 4.5. A similar trend was observed for the phosphate system, but the opposite was seen for the sulphate system. This suggests that the inhibition of sulphate on the adsorption of the organic acids decreased with the increase in pH, because the adsorption of sulphate decreased strongly with increasing pH. [source] Nanotubes: A Closer Look Inside Nanotubes: Pore Structure Evaluation of Anodized Alumina Templated Carbon Nanotube Membranes Through Adsorption and Permeability Studies (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Mater. In the "heart" of nanotubes. The internal morphology of carbon nanotubes (CNTs) is assessed by investigating the permeability and adsorption behavior of selected gases and vapors through CNTs that have been grown inside the channels of an anodized alumina template, as presented by G. E. Romanos, G. N. Karanikolos, and co-workers on page 2500. The cover illustrates template-free aligned CNTs in a heart-like configuration. Internal restrictions, surface roughness, hollow space narrowing, and other inside-tubes characteristics are determined that are crucial in CNT storage and flow-through applications. [source] The Influence of Surface Chemistry and Pore Size on the Adsorption of Proteins on Nanostructured Carbon MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Munusami Vijayaraj Abstract Carbon films are synthesized by templating of anodic aluminum oxide films. These carbon materials exhibit nanochannels with controlled diameter and length. Selected chemical treatments are done to tailor the surface chemistry. The adsorption capacities of bovine serum albumin and cytochrome c are measured by temperature-programmed desorption with mass spectrometry (TPD-MS) analysis and with conventional biological assays. The first method allows quantification of the proteins that exhibit strong interactions with the surface, while the second one is used to obtain the total adsorption capacity. Moreover, the TPD-MS profiles, which are related to the structural modifications of the proteins during the adsorption, show that strong interactions take place with hydrophobic surfaces. When oxygenated functions are present, the adsorption capacity increases and the nature of the interactions is modified. The ratio of irreversible to reversible adsorption is significantly different for the two proteins, and is slightly related to the surface chemistry. The influence of nanochannel size is studied: below 50 nm, the coverage ratio shows that access to the porosity is limited by diffusion in the channel and by pore plugging, in agreement with the strong interactions of proteins with the carbon surface. [source] A Closer Look Inside Nanotubes: Pore Structure Evaluation of Anodized Alumina Templated Carbon Nanotube Membranes Through Adsorption and Permeability StudiesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Georgios Pilatos Abstract Although hollow nanostructures, such as nanotubes, represent a major portion of nanoscaled materials with a tremendously large application range, a detailed evaluation of their internal characteristics still remains elusive. Transmission electron microscopy is the most common analytical technique to examine the internal configuration of these structures, yet it can only provide evidence of a minimal portion of the overall material, thus, it cannot be accurately generalized. In the present paper, in addition to electron microscopy and other spot-size analysis methods (X-ray diffraction, Raman spectroscopy, etc.), a combination of techniques including adsorption, permeability, and relative permeability are employed in order to provide important insights into various crucial details of the overall internal surface and hollow-space characteristics of carbon nanotube (CNT) arrays and membranes. The CNT arrays are fabricated using anodized alumina as a template in a flow-through chemical vapor deposition (CVD) reactor. This is the first systematic approach for investigating the internal configuration of template-based CNT arrays in detail. Key findings are made for the customized optimization of the resulting nanotube membranes for a variety of applications, including separations, nanofluidics and nanoreactors, biological capturing and purification, and controlled drug delivery and release. [source] Multifunctional Mesoporous Silica Material Used for Detection and Adsorption of Cu2+ in Aqueous Solution and Biological Applications in vitro and in vivoADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Qingtao Meng Abstract An inorganic,organic silica material (SBA,P2), prepared by immobilization of the 1,8-naphthalimide-based receptor P2 within the channels of the mesoporous silica material SBA-15, is characterized by transmission electron microscopy and several spectroscopic methods. SBA,P2 features a high affinity Cu2+ -specific fluorescence response in aqueous solution with a detection limit for Cu2+ of ca. 0.65,ppb (10,×,10,9,M) under optimized conditions. It can extract Cu2+ from the solution with only trace amounts remaining. Through isolating of the toxic ions within the mesopores of the silica, SBA,P2 has the potential to work as a toxicide for Cu2+ in living systems. The fluorogenical responses are reversible and do not vary over a broad (4.0 to 9.0) pH range suitable for application under physiological conditions. The fluorescence responses of Cu2+ in vitro (human breast cancer cells) and in vivo (five-day-old zebrafish) demonstrate the possibility of further application in biology. [source] Enhanced Adsorption of Ammonia on Metal-Organic Framework/Graphite Oxide Composites: Analysis of Surface InteractionsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Camille Petit Abstract Composites of the metal-organic framework (MOF), MOF-5, and graphite oxide (GO) with different ratios of the two components are prepared and tested in ammonia removal under dry conditions. The parent and composite materials are characterized before and after exposure to ammonia by sorption of N2, X-ray diffraction, thermal analyses, and FT-IR spectroscopy. The results show a synergetic effect resulting in an increase in the ammonia uptake compared to the parent materials. It is linked to enhanced dispersive forces in the pore space of the composites. Additionally, ammonia interacts with zinc oxide tetrahedra via hydrogen bonding and is intercalated between the layers of GO. Retention of a large quantity of ammonia eventually leads to a collapse of the MOF-5 structure in the composites. The effect resembles that observed when MOF-5 is exposed to water. Taking into account the similarity of ammonia and water molecules, it is hypothesized that ammonia causes a destruction of the MOF-5 and composite structure as a result of its hydrogen bonding with the zinc oxide clusters. [source] Ethanol and Acetaldehyde Adsorption on a Carbon-Supported Pt Catalyst: A Comparative DEMS StudyFUEL CELLS, Issue 1-2 2004H. Wang Abstract The adsorption of ethanol and acetaldehyde on carbon Vulcan supported Pt fuel cell catalyst and the electrochemical desorption of the adsorption products were studied, using electrochemical measurements and differential electrochemical mass spectrosmetry (DEMS), under continuous flow conditions. Faradaic current adsorption transients at different constant adsorption potentials, which also include CO adsorption for comparison, show pronounced effects of the adsorption potential and the nature of the reactant molecule. Acetaldehyde adsorption is much faster than ethanol adsorption at all potentials. Pronounced Had induced blocking effects for ethanol adsorption are observed at very cathodic adsorption potentials, < 0.16,V, while for acetaldehyde adsorption this effect is much less significant. Comparison of the adsorption charge for CO adsorption with the H-upd charge allows differentiation between H-displacement and double-layer charging effects. Continuous bulk oxidation is observed for both reactants at potentials > 0.31,V; for acetaldehyde adsorption, increasing bulk reduction is found at low potentials. Based on the electron yield per CO2 molecule formed and on the similarity with the CO stripping characteristics the dominant stable adsorbate is CO, coadsorbed with smaller amounts of (partly oxidized) hydrocarbon decomposition fragments, which are also oxidized at higher potentials (> 0.85,V) and which can be reductively desorbed as methane or, to a very small extent, as ethane. The presence of small amounts of adsorbed C2 species and the oxidative dissociation of these species in the main CO oxidation potential range is clearly demonstrated by increased methane desorption after a potential shift to 0.85,V. The data demonstrate that the Pt/Vulcan catalyst is very reactive for C-C bond breaking upon adsorption of these reactants. [source] Random Copolymer Films with Molecular-Scale Compositional Heterogeneities that Interfere with Protein AdsorptionADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Salmaan H. Baxamusa Abstract Smooth surfaces with compositional heterogeneities at a molecular-length scale are presented with the goal of disrupting surface,protein interactions. These surfaces are synthesized by utilizing photoinitiated chemical vapor deposition (piCVD) to deposit thin films of random copolymers consisting of highly hydrophilic and highly hydrophobic comonomers. Swellability, wettability, and surface roughness could be systematically controlled by tuning the copolymer composition. The surface composition was dynamic, and the surface reconstructed based on the hydration state of the film. Proteins adsorbed to the copolymer films less readily than to either of the respective homopolymers, indicating a synergistic effect resulting from the random copolymer presenting molecular-scale compositional heterogeneity. These results provide direct evidence that protein adsorption can be disrupted by such surfaces and a simple analytical model suggests that the heterogeneities occur over areas encompassing 4,5 repeat units of the polymer. The synthetic method used to create these films can be used to coat arbitrary geometries, enabling practical utility in a number of applications. [source] In Pursuit of Zero: Polymer Brushes that Resist the Adsorption of ProteinsADVANCED MATERIALS, Issue 23 2009Angus Hucknall Abstract Protein resistant or "non-fouling" surfaces are of great interest for a variety of biomedical and biotechnology applications. This article briefly reviews the development of protein resistant surfaces, followed by recent research on a new methodology to fabricate non-fouling surfaces by surface-initiated polymerization. We show that polymer brushes synthesized by surface-initiated polymerization that present short oligo(ethylene glycol) side chains are exceptionally resistant to protein adsorption and cell adhesion. The importance of the protein and cell resistance conferred by these polymer brushes is illustrated by their use as substrates for the fabrication of antibody microarrays that exhibit femtomolar limits of detection in complex fluids such as serum and blood with relaxed requirements for intermediate wash steps. This example highlights the important point that the reduction in background noise afforded by protein-resistant surfaces can greatly simplify the development of ultrasensitive heterogeneous, surface-based clinical and proteomic assays with increased sensitivity and utility. [source] A 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] Animal use replacement, reduction, and refinement: Development of an integrated testing strategy for bioconcentration of chemicals in fish,INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 1 2007Watze de Wolf Abstract When addressing the use of fish for the environmental safety of chemicals and effluents, there are many opportunities for applying the principles of the 3Rs: Reduce, Refine, and Replace. The current environmental regulatory testing strategy for bioconcentration and secondary poisoning has been reviewed, and alternative approaches that provide useful information are described. Several approaches can be used to reduce the number of fish used in the Organization for Economic Cooperation and Development (OECD) Test Guideline 305, including alternative in vivo test methods such as the dietary accumulation test and the static exposure approach. The best replacement approach would seem to use read-across, chemical grouping, and quantitative structure-activity relationships with an assessment of the key processes in bioconcentration: Adsorption, distribution, metabolism, and excretion. Biomimetic extraction has particular usefulness in addressing bioavailable chemicals and is in some circumstances capable of predicting uptake. Use of alternative organisms such as invertebrates should also be considered. A single cut-off value for molecular weight and size beyond which no absorption will take place cannot be identified. Recommendations for their use in bioaccumulative (B) categorization schemes are provided. Assessment of biotransformation with in vitro assays and in silico approaches holds significant promise. Further research is needed to identify their variability and confidence limits and the ways to use this as a basis to estimate bioconcentration factors. A tiered bioconcentration testing strategy has been developed taking account of the alternatives discussed. [source] Adsorption of water in mordenite,An ab initio studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2001Th. Demuth Abstract The adsorption of water in mordenite has been investigated using density functional theory using gradient corrections to the exchange,correlation functional. In the neutral complex water is strongly physisorbed through two different hydrogen bonds, the stronger between the acid site and the water oxygen atom, the weaker between a hydrogen atom of the adsorbed molecule and a framework oxygen atom. Strong polarizations and structural distortions of both the acid site and the molecule have been observed. To elucidate the question if a chemisorbed complex (creation of a hydroxonium ion) is possible, ab initio molecular dynamics have been performed, indicating that a protonation of water occurs even for the low coverage of one water molecule per unit cell. However, this ionic configuration cannot be stabilized by the electrostatic field of the zeolite framework and is therefore not a minimum of the potential energy surface. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 110,116, 2001 [source] Ochratoxin A removal in synthetic and natural grape juices by selected oenological Saccharomyces strainsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2004H. Bejaoui Abstract Aims:, To assess, for the first time the efficiency in removing ochratoxin A (OTA) from laboratory medium [yeast peptone glucose (YPG)], synthetic grape juice medium (SGM) and natural grape juice by viable and dead (heat and acid-treated) oenological Saccharomyces strains (five S. cerevisiae and one S. bayanus) compared with a commercial yeast walls additive. Methods and Results:, Levels of OTA during its interaction with six oenological Saccharomyces strains (five S. cerevisiae and one S. bayanus) or with a commercial yeast walls additive in YPG medium, in SGM or in natural grape juices was assessed by HPLC after appropriate extraction methods. A significant decrease of OTA levels in YPG medium and SGM was observed for many of the growing strains reaching a maximum of 45%, but no degradation products were detected. With both heat and acid pretreated yeasts, OTA removal was enhanced, indicating that adsorption, not catabolism, is the mechanism to reduce OTA concentrations. Adsorption was also improved when the yeast concentration was increased and when the pH of the medium was lower. Approximately 90% of OTA was bound rapidly within 5 min and up to 72 h of incubation with heat-treated cells of either S. cerevisiae or S. bayanus. A comparative study between heat-treated cells (HC) and commercial yeast walls (YW) (used as oenological additive), introduced at two different concentrations (0·2 and 6·7 g l,1) in an OTA-contaminated grape juice, showed the highest efficiency by HC to adsorb rapidly within 5 min the total amount of the mycotoxin. Conclusions:, Oenological S. cerevisiae and S. bayanus were able to remove ochatoxin A from synthetic and natural grape juices. This removal was rapid and improved by dead yeasts having more efficiency than commercial yeast walls. Significance and Impact of the Study:, The efficiency of heat-treated yeasts to remove OTA gives a new hope for grape juice and must decontamination avoiding negative impacts on human health. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||