Hydrophobic Beads Research Articles

Interaction of hemocytes and prophenoloxidase system of fifth instar nymphs of Acheta domesticus with bacteria

The hemocytes to which bacteria adhere were defined and the contribution of the prophenoloxidase system of fifth instar nymphs of Acheta domesticus to adhesion were examined. The physicochemical parameters affecting hemocyte and phenoloxidase activity were determined. Both plasmatocytes and granular cells responded to bacteria, the latter cells entrapping the microorganisms on filopodial extensions. The optimum pH for hemocyte adhesion to glass slides was 6.5, the granular cells being the most sensitive hemocyte type. Although hydrophobic resin beads and positively-charged beads favoured hemocyte attachment, these parameters did not contribute to differential bacterial adhesion to hemocytes. Activation of phenoloxidase was neither enhanced nor inhibited by 0.1 and 1 mg/ml of laminarin or zymosan nor by dead Bacillus subtilis. However, live B. subtilis activated the enzyme and dead Xenorhabdus nematophilus inhibited enzyme activation. Serine protease components of the prophenoloxidase system had opsonic properties for B. subtilis but not for X. nematophilus. Phenoloxidase activity was enhanced by Ca 2+ and Mg 2+ and inhibited by SO 2− 4 .

低粘度流出油回収用ブラシコンベアーの開発に関する研究

Chain brush skimmers have the brushes mounted on several continuous loop chains and oil is recovered by the bristles of brushes. The brushes are rotated through the oil/water interface and oil picked up on the brushes is combed from the bristles into a sump. The skimmers are effective in medium to very high oil viscosities and its performance does not degrade by small debris. However, the skimmers are not effective in low viscosity oil.Adhesion mechanism of low viscosity oil (heavy oil A) on the bristles of a brush was studied using hydrophilic and hydrophobic glass beads bed. Amount of oil adsorbed in the bed was proportional to the entry suction pressure. It was founded that the development of the entry suction pressure was required and the capillary diameter should be smaller than 0.392 mm to recover heavy oil A. The material of brush has no significant effect on the adsorption of heavy oil A which contains functional groups. However, oleophilic brush can be used for all kinds of oil. When recovering oil from an oil-water mixture about 30 to 40% water is also recovered.Recovery rate of low viscosity oil using model brush was calculated to be 10-12 m3/hr, almost with same performance reported for recovering medium to high viscosity oil by LBC system.

Community structure of biofilms on ennobled stainless steel in Baltic Sea water

400 mV), the biofilm on the steel surface was characterized using confocal laser scanning microscopy (CLSM) in combination with functional and phylogenetic stains. The biofilm consisted of microbial cell clusters covering 10–20% of the surface. The clusters were loaf-formed, with a basal diameter of 20–150 μm, 5–20 per mm−2, each holding >104 cells in a density of 1–5 × 107 cells mm−3. The typical cluster contained mainly small Gram-negative bacteria (binding the EUB338 probe when hybridized in situ on the steel surface), and often carried one to three spherical colonies, either homogeneously composed of large Gram-negative cocci or more often small bacterial rods in high density, 108–109 cells mm−3. The clusters in live biofilms contained no pores, and clusters over 25 μm in diameter had a core nonpenetrable to fluorescent nucleic acid stains and ConA lectin stain. Fluorescently-tagged ConA stained cells at a depth of 10 cells in a stack) into the cluster than did the less polar dyes SYTO 16 (log Kow 1.48) and acridine orange (log Kow 1.24), which stained five cells in a stack. Fluorescent hydrophobic and hydrophilic latex beads (diameter 0.02, 0.1 or 1.0 μm) coated patchwise the cluster surface facing the water, but penetrated only to depths of ⩽2 μm indicating a permeability barrier. About 1/3 of the stainable cells hybridized in situ with Alf1b, while fewer than 1/7 hybridized to GAM42, probes targeted towards α- and γ-Proteobacteria, respectively. Our results represent a microscopic description of an ennobling biofilm, where the ennoblement could follow the sequence of redox events as suggested by the model of Dickinson and Lewandowski (1996) for the structure of corrosive biofilms on a steel surface.

An automatic Bio-Beads-supplying device for two-dimensional crystallization of membrane proteins

A simple device has been developed for the automatic supply of hydrophobic resin beads simultaneously to many sample solutions. The device enables the programmed removal of various types of nonionic detergents often used for two-dimensional crystallization of membrane proteins.

Embedded conformon model of chain folding

The real-space renormalization-group technique is used to study the low lying energy states of a random copolymer composed of hydrophobic (H) and polar (P) beads on a simple cubic lattice. Application of a variety of boundary conditions to parts of the larger chain (embedded conformons) while progressively increasing the length scale gives the lowest energy states in agreement with exact calculations for a 17 bead chain with a random H,P sequence. These results are significant for studying minimalist models of the folding of complex molecules because the computation time is several orders of magnitude less than for other approaches.

Embedded conformon model of chain folding

The real-space renormalization-group technique is used to study the low lying energy states of a random copolymer composed of hydrophobic (H) and polar (P) beads on a simple cubic lattice. Application of a variety of boundary conditions to parts of the larger chain (embedded conformons) while progressively increasing the length scale gives the lowest energy states in agreement with exact calculations for a 17 bead chain with a random H,P sequence. These results are significant for studying minimalist models of the folding of complex molecules because the computation time is several orders of magnitude less than for other approaches.

Surface Active Substrates Essential in Lipase-Mediated Esterifications in Foams

Foam offers an appropriate surface to perform lipase-mediated reactions. Aqueous foam, a colloidal dispersion of air in water, offers a very high substrate surface to solvent volume ratio for lipases to act. Esterification, an unfavorable reaction in water, could be efficiently done by lipase in aqueous foams made of lipase substrates. Esterification of oleic acid with a homologous series of aliphatic alcohols of varying length showed that surface excess property of both the substrates is essential for ester formation. The direction of lipase reaction is governed by the composition of the reactants in the interface. Similar reactions could be done in water with substrates adsorbed on hydrophobic beads. Foam-based reactions offer a simple, cheaper and environment-friendly method to conduct lipase-mediated reactions.

Use of Poloxamer Polymers to Stabilize Recombinant Human Growth Hormone Against Various Processing Stresses

ABSTRACTSeveral processing and shipping stresses were investigated for their effect on the physical stability of recombinant human growth hormone (rhGH). These included exposure to air/water interfaces, adsorption to hydrophobic surfaces, freeze-thaw cycles, and temperature. The interfacially and thermally denatured hormone was evaluated for the presence of insoluble and soluble aggregates by spectrophotometry and by size-exclusion chromatography, respectively. Noncovalent aggregates were generated by either vortexing or multiple passages through a hypodermic needle, processes which exposed the protein to air/water interfaces. Thermal stress also resulted in the generation of aggregates. This aggregation was reduced or eliminated by the use of poloxamer polymers. Under the conditions employed, filtration through some commercially available filters, exposure to hydrophobic beads, or multiple freeze-thaw cycles did not produce any aggregates within the limitations of the analytical procedures used. Based on this study, Poloxamer 407 was found to be the most effective stabilizer for rhGH for protection against interfacial and thermal stress.

Enhanced and Retarded Drug Release from Hydrophobic Ionic Beads

Abstract The effect of drug solubility and drug loading on the kinetics of polymer ionization and drug release from poly(methyl methacrylate-co-methacrylic acid) (PMMA/MAA) beads has been investigated. Acebutalol HCl, labetalol HCl, and propranolol HCl were chosen as model drugs, representing a range of liphophilicity. Polymer ionization and drug release rates increase with drug loading for a highly water-soluble drug, i.e., acebutalol HCl. Drug release and ionization rates, however, decrease with drug loading up to 11.0 and 12.2% for less water-soluble drugs, i.e., labetalol HCl and propranolol HCl, respectively, and then increase above the loading level of 18.6%. This decrease in rate is attributable to the low solubility of the drug, resulting in its slow diffusion and the need for increased electrolyte uptake to ionize the acidic components (i.e., polymer matrix and HCl). At a loading level below 18.6%, the ionization kinetics were governed by intraparticle diffusion and chemical reaction resistances, with an additional minor contribution from film diffusion resistance. At higher loading, above 24.6% of acebutalol HCl, however, the film diffusion resistance controlled the overall ionization kinetics of drug-loaded PMMA/MAA beads.

Effect of ionic strength and ionic species on partitioning behavior of hydrophobic and hydrophilic polystyrene latex beads in aqueous two-phase polymer systems

The effects of ion type, pH, ionic strength and colloidal surface properties on the partitioning of three different types of polystyrene latex beads with different surface properties in the two-phase polyethylene glycol (PEG)/dextran (DEX) system have been measured. Certain inorganic monovalent ion types alter the partitioning of hydrophilic polystyrene beads from the top PEG-rich phase to the bottom DEX-rich phase, while hydrophobic polystyrene beads always partition into the top PEG-rich phase, regardless of the type and concentration of salt. The partitioning of the hydrophilic beads depends on the ionic strength as well as the ion type, and is not due to changes in pH. Strong water-structure-making salts, e.g. ammonium sulfate, are least likely to induce partitioning to the bottom phase, while sodium azide, a pseudo halide, has the strongest effect on partitioning of the beads. The Hofmeister series does not predict the relative effectiveness of the different ions that do alter the partitioning of the hydrophilic beads. The polyacrylic acid (PAA) coating on the hydrophilic beads is known to strongly interact with PEG and polyoxyethylene (PEO) polymers, via hydrogen bonding, especially at lower pH values. This strong polymer-polymer interaction may be disrupted by many salts, e.g. sodium chloride, at higher ionic strengths. In general, the influence of ions on the conformation, solvation and free energy of PEG in aqueous solution, and its interaction with PAA, is a complex phenomenon and is not predicted by existing theories. Depletion flocculation may also play a role in the salt-dependent bead partitioning behavior. A general consequence of the acid-PEG interaction is that relatively hydrophilic solutes with many surface carboxylic acid groups may partition to the top PEG-rich phase, even though it is the less polar of the two phases in the PEG/DEX system. This phenomenon may explain the partitioning behavior as a function of salt observed for certain species of bacteria.

Application of Shrinking-Core Model for Ionization of Hydrophobic Ionic Beads

AbstractA model based on the pseudo-steady-state shrinking core for the ionization of PMMA/MAA beads is presented. This accounts for the film mass transfer, intraparticle diffusion, and chemical reaction resistances in series. The film mass transfer resistance plays a minor role in the overall ionization process for the range of experiments studied herein. The specific reaction rate constants and diffusion coefficients increase as the pH of phosphate buffer increases, due to the increased accessibility of hydroxide ion and increased swelling of the gel layer, respectively; the specific reaction rate constants and diffusion coefficients are little influenced by the change of ionic strength of the phosphate buffer. The model shows that the rate of ionization depends upon the concentration of the buffer solution.

Structural effect of galactose residue in synthetic glycoconjugates on interaction with rat hepatocytes

N-p-Vinylbenzyl-O-beta-D-galactopyranosyl-(1,4)-D-gluconamide++ + (PVLA) has been used as an asialoglycoprotein model polymer. Rat hepatocytes expressing asialoglycoprotein receptors are capable of binding to hydrophobic plastic dishes coated with PVLA. PVLA, water-soluble polystyrene derivatives bearing galactose residues preferentially adsorb to plastic plates made of polystyrene rather than those of poly(methyl methacrylate). Hence, we modified chitosan beads with linear chains composed of a long alkyl or phenyl moiety to study the effect of structural variations of adsorbed PVLA, and investigated the extent of hepatocyte attachment to the hydrophobic beads coated with PVLA. The attachment was independent of the amount of immobilized PVLA; rather, it was dependent on the hydrophobicity of the beads with PVLA. To simplify the surface of the hydrophobic beads with PVLA, galactopyranoses were covalently linked to chitosan beads via hydrophobic spacer arms, and hepatocyte attachment was compared among the prepared beads. The beads with spacer arms containing phenylalanine and a phthalic moiety showed increased hepatocyte attachment, which was elicited by galactose residues on the beads. These results suggest that rotational restriction or stiffness and hydrophobicity due to the phenyl moiety are essential to enhance the specificity of terminal galactose in PVLA. This analysis contributes to the design and optimization of an artificial ligand for cellular receptors recognizing sugar moieties.

Kinetics at the collapse transition of homopolymers and random copolymers

We describe the results of Monte Carlo simulations for kinetics at the collapse transition of a homopolymer in a lattice model. We find the kinetic laws corresponding to the three kinetic stages of the process: R2g(t)=R2g(0)−At7/11 at the early stage corresponding to formation and growth of locally collapsed clusters, the coarsening stage is characterized by growth of clusters according to the law S∝t1/2, where S is the average number of Kuhn units per cluster, and the final relaxation stage is described by the law R2g(t)=R2g(∞)+A1(1)e−t/τ1(1) with τ1(1)∝N2. We also present preliminary results on the equilibrium properties and ‘‘collapse’’ transition of a random copolymer. The transition curve is determined as a function of hydrophobic bead concentration na. We discuss the different collapsed copolymer states as a function of the composition. At low hydrophilicity we believe the critical value of the interaction parameter is governed by the law χc(na)∝na−2/3. In the kinetics we see unusual phenomena such as the appearance of a metastable long-lived states with few clusters and nontrivial loop structure.

Adsorption and coagulability of fibrinogen on atheromatous lipid surfaces.

Fibrinogen, the precursor of the blood clot matrix and a major constituent of atherosclerotic lesions, is shown to adsorb with high affinity to hydrophobic beads coated with cholesteryl oleate, cholesterol, or loosely packed lecithin. The quantity of fibrinogen that binds to cholesterol- or lecithin-coated beads decreases as the surface concentration of the lipid increases; densely packed films lecithin bind little,if any, if the protein. In sharp contrast, the appreciable quantity of fibrinogen that binds to cholesteryl oleate-coated beads is indifferent to the surface concentration of that lipid. Not unexpectedly, the quantity of fibrinogen that binds to beads coated with mixtures of cholesteryl oleate and lecithin increases with increasing concentration of the cholesteryl ester. When bound, fibrinogen can be converted by thrombin to fibrin and nucleate clot formation as manifested by the aggregation of stirred beads. These results indicate that hydrophobic, atheromatous lipid surfaces, particularly those rich in cholesteryl esters, may be predisposed to thrombosis by virtue of their inherent capacity to bind functional fibrinogen.

Computer simulation of protein refolding pathways and intermediates

AbstractComputer simulation studies of refolding pathways and the formation of intermediates for a simple, 2–D lattice protein model are presented. The sequence of the 20–bead model protein chain is chosen so that hydrophobic beads will reside in the protein interior in the native state. Nonbonded hydrophobic beads attract each other with strength ϵ decreasing the |ϵ/kT| mimics increasing the concentration of the denaturant. Dynamic Monte Carlo simulations and exhaustive conformational searches have been performed on an isolated model protein sequence at different levels of |ϵ| (different denaturant concentrations). As the denaturant is withdrawn, the model protein exhibits a transition from a random coil state to a compact native state with a hydrophobic core. The refolding process is observed to be cooperative in that the chain does not start folding until the middle section has folded correctly, and proceeds along preferred pathways that are populated by distinct, partially folded intermediates.

Uniform-size hydrophobic polymer-based separation media selectively modified with a hydrophilic external polymeric layer

A simple procedure for the preparation of macroporous hydrophobic styrene-divinylbenzene polymeric separation media with a hydrophilic outer surface has been developed. A hydrophilic monomer and water-soluble polymerization initiator are added to the reaction mixture during the final polymerization step of the preparation of size-monodisperse particles. Because the hydrophobic styrene-divinylbenzene framework of the beads is already formed, and the hydrophilic monomer does not penetrate the pores of the beads that are filled with a hydrophobic porogen, the hydrophilic layer is formed only at the surface of the beads. The hydrophilic monomers used included glycerol monomethacrylate and glycerol dimethacrylate and toluene was used as the porogen for the poly(styrene-co-divinylbenzene) beads. Comparative experiments involving beads with or without a hydrophilic medium showed that the separation selectivity of the media towards hydrophobic solutes remains unchanged. However, the modified medium with a hydrophilic layer could be used to analyse mixtures that also contained large peptide molecules as these do not adsorb at its surface as is the case with the unmodified hydrophobic beads.

Complement activation on solid surfaces as determined by C3 deposition and hemolytic consumption.

Complement activation was investigated on hydrophilic and hydrophobic glass beads incubated in serum. Very little complement activation was detected with these surfaces, as indicated by a hemolytic assay and by measurement of the amount of iC3b appearing in the solution. However, preadsorption with IgG at the hydrophobic and hydrophilic beads resulted in complement activation on both surfaces. We also investigated dependent deposition of C3 at hydrophobic and hydrophilic silicon surfaces when the complement was activated. The chemistry of those surfaces is similar to the hydrophobic and hydrophilic beads. Ellipsometry, an optical method, was used for determination of the amounts of organic material deposited at the surface. C3 deposition was observed at the IgG precoated hydrophobic surface but not at the IgG-coated hydrophilic surface. The absence of C3 deposition at the hydrophilic surface was probably due to reversible binding of IgG. However, precoating of the hydrophilic surface with a double layer of IgG and anti-IgG resulted in C3 deposition also at the hydrophilic surface. The results illustrate that methods based on measuring deposition of C3 at surfaces, such as immunofluorescence or ellipsometry, cannot exclude surface-associated complement activation that is probably due to reversible binding of the complement components of the activated molecule. On the other hand, it has previously been shown that determination of complement activation in solution with the use of a C3a assay cannot exclude surface-associated activation due to immobilization of C3a at the surface. This methodologic question is an important issue because factors such as C3a and C5a act as soluble anaphylatoxins, whereas deposited factors such as C3 act as cellular receptors.

Minimum energy compact structures of random sequences of heteropolymers.

We enumerate the number of minimum energy compact structures (MECS) for a two dimensional heteropolymer model consisting of hydrophobic (H) and hydrophilic beads averaged over all possible sequences as a function of the total number of beads N and the number of H beads ${\mathit{N}}_{\mathit{H}}$. The analysis of the average number of compact structures, which grows exponentially with N, gives no indication of logarithmic corrections to the free energy. For intermediate values of the ratio ${\mathit{N}}_{\mathit{H}}$/N, we estimate that the average number of MECS\char22{}which has a minimum at ${\mathit{N}}_{\mathit{H}}^{\mathrm{min}}$/N=0.6\ifmmode\pm\else\textpm\fi{}0.1\char22{}does not grow with N. Our results suggest that the late stages of protein folding should be restricted to the sampling of MECS only.

Silica beads induce cellular and humoral immune responses in Galleria mellonella larvae and in isolated plasmatocytes, obtained by a newly adapted nylon wool separation method

Intrahaemocoelic injection of silica beads into Galleria mellonella (wax moth) larvae provoked strong cellular and humoral reactions similar to those normally occuring during an antibacterial defence. The cellular reactions of the haemocytes—investigated by light and scanning electron microscopy—comprised degranulation of granular cells and phagocytosis by plasmatocytes. The humoral responses—measured in cell free haemolymph as the increase of antibacterial activity against Echerichia coli K12 D31 and of lysozyme activity against Micrococcus luteus cell walls—were significantly enhanced in comparison to controls. Only hydrophylic but not hydrophobic silica beads provoked strong reactions. Plasmatocytes (PLs), the main phagocytic haemocytes of G. mellonella, were isolated by using a newly adapted nylon wool column technique. PL monolayers, prepared from isolated cells, exhibited a high purity by consisting of at least 90% PL. Scanning electron microscopy studies revealed that 64% of the isolated PLs showed phagocytic activity against the sterile silica beads in vitro. Intrahaemocoelic injection of supernatants from monolayers with phagocytosing plasmatocytes into naive larvae led to a clearly higher antibacterial activity against E. coli in haemolymph of recipients than the injection of supernatants from monolayers with non-phagocytosing cells. The earlier supposition that haemocyte-released factors induce the humoral immune response is further supported by these results.

Spreading of hydrophobic silica beads at water—air interfaces

Structured monoparticle layers, formed from 3 ± 1 μm diameter silica beads silylated to a greater (sample A) and a lesser (sample B) extent, have been investigated on water and on aqueous 1.0 M NaCl subphases in a Langmuir film balance. Hydrophobicities corresponding to the different extents of silylation were estimated by determining the wettabilities of identically treated 10 ± 1 μm silica beads. The advancing water contact angles of 98 ± 4° and 76 ± 4° have been calculated for samples A and B respectively. Visual observations of spreading and redispersity, and determinations of surface pressure—surface area isotherms, hysteresis and contact cross-sectional areas led to the assessment of the structural strengths of these two sets of silica beads. Appreciably stronger attractive interactions between neighboring silica beads have been found in structured monoparticle layers prepared from sample A than those formed from sample B. The less hydrophobic silica beads (sample B) were postulated to be separated from each other by a layer of water molecules in the structured monoparticle layer. This postulate has been supported by calculating the total interparticle interaction energies by applying the DLVO theory. Introduction of 1.0 M NaCl did not appreciably affect the behavior of structured monoparticle layers prepared from sample A. Significant creasing was observed, however, in the vicinity of the moving barrier upon the compression of structured monoparticle layers prepared from sample B.