Search results for "Charge"
showing 10 items of 4686 documents
Biologically-induced transition of bio-silica sol to mesoscopic gelatinous flocs: a biomimetic approach to a controlled fabrication of bio-silica str…
2012
Siliceous sponges form their skeletal elements, the spicules, enzymatically via the sponge-specific enzyme silicatein. The enzymatic product of silicatein in vitro is a bio-silica polymer that is not processed/hardened by phase separation. In the present study we applied a two-phase system to investigate the transition of bio-silica, formed by silicatein, from the lucid state to the opaque/turbid state. We report for the first time that the polyether polyethylene glycol [PEG] causes a rapid transition of the lucid bio-silica to the opaque/turbid state. For the experiments the recombinant silicatein from the demosponge Suberites domuncula had been used. This process is rapid (1 h) and procee…
Label-Free Detection of Protein-Ligand Interactions by the Quartz Crystal Microbalance
2005
In recent years the quartz crystal microbalance (QCM) has been accepted as a powerful technique to monitor adsorption processes at interfaces in different chemical and biological research areas. In the last decade, the investigation of adsorption of biomolecules on functionalized surfaces turned out to be one of the paramount applications of the QCM comprising the interaction of nucleic acids, specific molecular recognition of protein-receptor couples, and antigen-antibody reactions realized in immunosensors. The advantage of the QCM technique is that it allows for a label free detection of molecules. This is a result of the fact that the frequency response of the quartz resonator is propor…
Species-specific aggregation factor in sponges : VIII. Nature and alteration of cell surface charge.
1977
Isolated cells from the siliceous spongeGeodia cydonium have been studied with respect to their partition behaviour in a two-phase aqueous polymer system. With this method it is possible to determine subtle changes in the cell surface charge. Addition of a homologous aggregation factor to the isolated cells lowers the partition rate, a finding which indicates that after binding of the aggregation factor to the cells their surface charge is reduced. The partition rate of the cells is strongly correlated with their content of membranebound sialic acid. Sixty-nine percent of the total, membrane-bound hexuronic acid is associated with the aggregation receptor; 1.8×107 aggregation receptor molec…
Photocatalytic degradation of organic compounds in aqueous systems by transition metal doped polycrystalline TiO2
2002
Abstract Some probe catalytic photooxidation reactions with aliphatic and aromatic organic compounds having different acid strengths, i.e. methanoic acid, ethanoic acid, benzoic acid and 4-nitrophenol, were carried out in aqueous systems by using polycrystalline TiO2 powders doped with various transition metal ions (Co, Cr, Cu, Fe, Mo, V and W). The Co-doped powder showed to be more photoactive than the bare TiO2 for methanoic acid degradation while the behaviour of TiO2/Cu and TiO2/Fe was similar to that of the support. TiO2/W was the most efficient sample for the photodegradation of benzoic acid and 4-nitrophenol, TiO2 the most active powder for ethanoic acid. A tentative explanation is p…
Ionic polymers based on dextran: hydrodynamic properties in aqueous solution and solvent mixtures.
2009
Hydrodynamic properties of a series of ionic polysaccharides with different charge density but the same molecular weight have been evaluated in salt-free aqueous solution and aqueous/organic solvent mixtures by means of capillary viscometry. The polyelectrolytes investigated contain quaternary ammonium salt groups, N-ethyl-N,N-dimethyl-2-hydroxypropylammonium chloride, attached to a dextran backbone. The experimental viscometric data have been plotted in terms of the Wolf method. The results show that the experimental data fit well with this model and allow the calculation of intrinsic viscosities and other hydrodynamic parameters, which provide new information about the dependence of the p…
Solution properties of polyelectrolytes
1993
Abstract Aqueous size-exclusion chromatography was used to analyse the elution behaviour of several standard ionic polymers, including poly( l -glutamic acid), sodium poly(styrene sulphonate) and poly(acrylic acid), different in nature and chain flexibility, as a function of the pH and ionic strength of the eluent. Two organic-based hydrophilic packings, Spherogel TSK PW4000 and Ultrahydrogel 250, were tested in order to select the optimal conditions of macromolecular separation, and the results obtained for each column were compared. A set of calibration graphs for the above polyions as a function of eluent pH and ionic strength were obtained and compared with those obtained for uncharged …
Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination
2021
Charged hydrogels are capable of swelling in aqueous salt solutions, whereby part of the salt ions is repelled due to the presence of fixed charged groups inside the hydrogel. This effect creates a concentration gradient between the absorbed solution and the surrounding fluid known as salt partitioning, offering a potential for these materials to be employed to desalinate saltwater. If the charged hydrogels are thermo-sensitive as well, then the purer, absorbed solution can be recovered by shrinking the hydrogels upon temperature change. To tailor that potential in water-purification and desalination applications, the main parameters influencing the salt partitioning, the deswelling of the …
A new class of ZnIIand CrIIIporphyrins incorporated into porous polymer matrices via an atmospheric pressure plasma enhanced CVD to form gas sensing …
2014
Designed ZnII and CrIII porphyrins (ZnIIP, CrIIIP(Cl)(H2O)) and conventional ZnIITPP and CrIIITPP(Cl)(H2O) are immobilized into porous polysiloxane films via chemical vapor deposition enhanced by an atmospheric pressure dielectric barrier discharge. UV/vis spectroscopy and mass spectrometry prove the integrity of the chromophores after the plasma treatment. The optical amine sensing capabilities of the films are investigated spectroscopically on exposure to triethylamine vapors. A series of coatings with different porphyrin loadings indicate influences of the deposition conditions on the growth of the sensing films and hence the device performance. Additionally, the synthesis and characteri…
Buildup of ultrathin multilayer films by a self-assembly process: III. Consecutively alternating adsorption of anionic and cationic polyelectrolytes …
1992
A solid substrate with a positively charged planar surface is immersed in a solution containing an anionic polyelectrolyte and a monolayer of the polyanion is adsorbed. Since the adsorption is carried out at relatively high concentrations of polyelectrolyte, a large number of ionic residues remain exposed to the interface with the solution and thus the surface charge is effectively reversed. After rinsing in pure water the substrate is immersed in the solution containing a cationic polyelectrolyte. Again a monolayer is adsorbed but now the original surface charge is restored. By repeating both steps in a cyclic fashion, alternating multilayer assemblies of both polymers are obtained. The bu…
Persistent photovoltage in methylammonium lead iodide perovskite solar cells
2014
Open circuit voltage decay measurements are performed on methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells to investigate the charge carrier recombination dynamics. The measurements are compared to the two reference polymer-fullerene bulk heterojunction solar cells based on P3HT:PC60BM and PTB7:PC70BM blends. In the perovskite devices, two very different time domains of the voltage decay are found, with a first drop on a short time scale that is similar to the organic solar cells. However, two major differences are also observed. 65-70% of the maximum photovoltage persists on much longer timescales, and the recombination dynamics are dependent on the illumination intensity.