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Silica Beads (silica + bead)

Distribution by Scientific Domains

Chemistry	70%
Life Sciences	20%

Selected Abstracts

Cell Adhesion onto Highly Curved Surfaces: One-Step Immobilization of Human Erythrocyte Membranes on Silica Beads

CHEMPHYSCHEM, Issue 7 2003
Stefan Kaufmann
Abstract This paper deals with single-step, orientation-selective immobilization of human erythrocyte membranes on bare silica beads with different topographies: 1) solid (nonporous) silica beads with a diameter of 3 ,m and 2) porous silica beads with a diameter of 5 ,m. Erythrocyte membranes were immobilized onto beads simply by incubation, without sonication or osmotic lysis. Membrane orientation before and after immobilization was identified with two immunofluorescence labels: 1) the extracellular part of glycophorin can be labeled with a first monoclonal antibody and a second polyclonal antibody with fluorescence dyes (outside label), while 2) the cytoplasmic domain of Band 3 can be recognized with a first monoclonal antibody and a second fluorescent polyclonal antibody (inside label). Adherent erythrocytes on the beads all ruptured, inverted the asymmetric orientation of the membrane, and selectively exposed their cytoplasmic domain. The surface topography did not influence the orientation or the amount of immobilized membrane. On the other hand, the fact that no adsorption or rupture of erythrocytes could be observed on planar quartz substrates suggests a significant influence of contact curvature on adhesion energy. [source]

Antimicrobial peptide interactions with silica bead supported bilayers and E. coli: buforin II, magainin II, and arenicin,

JOURNAL OF PEPTIDE SCIENCE, Issue 8 2009
Ryan W. Davis
Abstract Using the unique quantitative capabilities of hyperspectral confocal microscopy combined with multivariate curve resolution, a comparative approach was employed to gain a deeper understanding of the different types of interactions of antimicrobial peptides (AMPs) with biological membranes and cellular compartments. This approach allowed direct comparison of the dynamics and local effects of buforin II, magainin II, and arenicin with nanoporous silica bead supported bilayers and living E. coli. Correlating between experiments and comparing these responses have yielded several important discoveries for pursuing the underlying biophysics of bacteriocidal specificity and the connection between structure and function in various cellular environments. First, a novel fluorescence method for direct comparison of a model and living system is demonstrated by utilizing the membrane partitioning and environmental sensitivity of propidium iodide. Second, measurements are presented comparing the temporal dynamics and local equilibrium concentrations of the different antimicrobial agents in the membrane and internal matrix of the described systems. Finally, we discuss how the data lead to a deeper understanding of the roles of membrane penetration and permeabilization in the action of these AMPs. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. [source]

Determination of Diclofenac in Urine Samples by Molecularly-Imprinted Solid-Phase Extraction and Adsorptive Differential Pulse Voltammetry

ELECTROANALYSIS, Issue 15 2007
Laura Fernández-Llano
Abstract A molecularly imprinted polymer for diclofenac (DCF) was prepared by thermal polymerization over silica beads using 2-(dimethylamino)ethyl-methacrylate as functional monomer. After silica elimination by HF treatment, the polymer was applied to the selective solid-phase extraction of the drug from urine followed by its quantification by adsorptive differential pulse voltammetry. Results indicate that the drug could be selectively extracted from the sample and quantified at clinically relevant concentrations (,g/mL). [source]

A 3-D dielectrophoretic filter chip

ELECTROPHORESIS, Issue 7 2007
Ciprian Iliescu Dr.
Abstract The paper presents a 3-D filter chip employing both mechanical and dielectrophoretic (DEP) filtration, and its corresponding microfabrication techniques. The device structure is similar to a classical capacitor: two planar electrodes, made from a stainless steel mesh, and bonded on both sides of a glass frame filled with round silica beads. The solution with the suspension of particles flows through both the mesh-electrodes and silica beads filter. The top stainless steel mesh (with openings of 60,,m and wires of 30,,m-thickness) provides the first stage of filtration based on mechanical trapping. A second level of filtration is based on DEP by using the nonuniformities of the electric field generated in the capacitor due to the nonuniformities of the dielectric medium. The filter can work also with DC and AC electric fields. The device was tested with yeast cells (Saccharomyces cerevisae) and achieved a maximal trapping efficiency of 75% at an applied AC voltage of 200,V and a flow rate of 0.1,mL/min, from an initial concentration of cells of 5×105 cells/mL. When the applied frequency was varieted in the range between 20 and 200,kHz, a minimal value of capture efficiency (3%) was notticed at 50,kHz, when yeast cells exhibit negative DEP and the cells are repelled in the space between the beads. [source]

Preparation of novel acrylamide-based thermoresponsive polymer analogues and their application as thermoresponsive chromatographic matrices

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008
Yoshikatsu Akiyama
Abstract New thermoresponsive polymers based on poly(N -(N, -alkylcarbamido)propyl methacrylamide) analogues were designed with increased hydrophobic content to facilitate temperature-dependent chromatographic separations of peptides and proteins from aqueous mobile phases. These polymer solution exhibited a lower critical solution temperature (LCST) when the alkyl group is methyl, ethyl, isopropyl, propyl, butyl, and isobutyl. However, larger alkyl groups such as hexyl and phenyl were not soluble in aqueous solutions at any temperature. Phase transition temperatures were lower for larger alkyl groups and increased with decreasing polymer molecular weight and concentration in solution. LCST dependence on polymer molecular weight and concentration is more significant compared with well-studied poly(N -isopropylacrylamide) (PIPAAm). Partition coefficient (log P) values for N -(N, -butylcarbamide)propylmethacrylamide and N -(N, -isobutylcarbamide)propyl methacrylamide (iBuCPMA) monomers are larger than that for IPAAm monomer, suggesting higher hydrophobicity than IPAAm. Chromatographic evaluation of poly(N -(N, -isobutylcarbamide)propyl methacrylamide) (PiBuCPMA) grafted silica particles in aqueous separations revealed larger k, values for peptides, insulin, insulin chain B, and angiotensin I than PIPAAm-grafted silica beads. In particular, k, values for insulin obtained from PiBuCPMA-grafted silica separations were much larger than those from PIPAAm-grafted surface separations, indicating that PiBuCPMA should be more hydrophobic than PIPAAm. These results support the introduction of alkylcarbamido groups to efficiently increase thermoresponsive polymer hydrophobicity of poly(N -alkylacrylamides) and poly(N -alkylmethacrylamides). Consequently, poly(N -(N, -alkylcarbamido)propyl methacrylamide) analogues such as PiBuCPMA and poly(N -(N, -alkylcarbamido)alkylmehacrylamide) are new thermoresponsive polymers with appropriate hydrophobic partitioning properties for protein and peptide separations in aqueous media, depending on selection of their alkyl groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5471,5482, 2008 [source]

Preparation, characterisation and modification of carbon-based monolithic rods for chromatographic applications

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2010
Ali H. Eltmimi
Abstract A range of porous carbon-based monolithic (PCM) rods with flow-through pore sizes of 1, 2, 5 and 10,,m, were produced using a silica particle template method. The rods were characterised using SEM and energy-dispersive X-ray spectroscopy, BET surface area and porous structure analysis, dilatometry and thermal gravimetry. SEM evaluation of the carbon monolithic structures revealed an interconnected rigid bimodal porous structure and energy-dispersive X-ray spectroscopy analysis verified the quantitative removal of the embedded silica beads. The specific surface areas of the 1, 2, 5 and 10,,m rods were 178, 154, 84 and 125,m2/g after pyrolysis and silica removal, respectively. Shrinkage of the monolithic rods during pyrolysis is proportional to the particle size of the silica used and ranged from 9 to 12%. Mercury porosimetry showed a narrow distribution of pore sizes, with an average of ,700,nm for the 1,,m carbon monolith. The suitability of bare and surface oxidised PCM rods for the use as a stationary phase for reversed and normal phase LC was explored. The additional modification of PCM rods with gold micro-particles followed by 6-mercaptohexanoic acid was performed and ion-exchange properties were evaluated. [source]

Cell Adhesion onto Highly Curved Surfaces: One-Step Immobilization of Human Erythrocyte Membranes on Silica Beads

SIMPLE METHOD FOR RNA PREPARATION FROM CYANOBACTERIA,

JOURNAL OF PHYCOLOGY, Issue 5 2006
Byung-Hyuk Kim
A simple and rapid method is presented for the preparation of RNA from various cyanobacteria. Unlike other methods that require a lysis solution, lysozymes, or proteinase K, the proposed method, called the bead,phenol,chloroform (BPC) method, uses silica/zirconia beads, phenol, and chloroform to break the cells and extract RNA more efficiently. Experiments confirm that the BPC method can successfully isolate total RNA from various cyanobacterial strains without DNA contamination, and the extracted RNA samples have a relatively high purity, concentration, and yield. Furthermore, the BPC method is more rapid, simple, and economical when compared with previously reported methods. [source]