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At least 235 records · Page 13Linked to original sources
PubMed1997

Direct coating of poly(lys) or acetyl-thio-acetyl peptides to polystyrene: the effects in an enzyme-linked immunosorbent assay.

Direct adsorption of small peptides to polystyrene surfaces is often not satisfactory. Therefore, a simple and general coating procedure to improve the coating efficiency of small synthetic peptide antigens to polystyrene is described. In this study, the binding capacities of four small synthetic peptides N-terminally linked to various moieties during synthesis were compared to their parent counterparts in terms of the amount of peptide coat concentration required to achieve 50% of the maximum enzyme-linked immunosorbent assay signal. Elongation of a short epitope sequence by an N-terminal acetyl-thio-acetyl (Ata) group or a lysyl moiety resulted in an enormous reduction in peptide coat concentration for all tested peptides of net two to four orders of magnitude when corrected for chain elongation. The optimal length of the lysyl moiety depended on the length of the model peptide. Replacement of both extensions by analogues (i.e., Ata analogues and other basic amino acid residues in the case of the lysyl moiety) was possible without reducing their enhancing properties to a great extent. Additional experiments showed that a lysyl moiety consisting of a linear stretch of seven lysyl moiety consisting of a linear stretch of seven lysyl residues was more effective in comparison to a branched lysyl construct and could easily compete with the multiple antigen peptide approach.

Acetylation↗
PubMed2002

Effect of Cd(2+) and Hg(2+) on the activity of Na(+)/K(+)-ATPase and Mg(2+)-ATPase adsorbed on polystyrene microtiter plates.

In the present study a polystyrene microtiter plate was tested as a support material for synaptic plasma membrane (SPM) immobilization by adsorption. The adsorption was carried out by an 18-h incubation at +4 degrees C of SPM with a polystyrene matrix, at pH 7.4. Evaluation of the efficiency of the applied immobilization method revealed that 10% protein fraction of initially applied SPM was bound to the support and that two SPM enzymes, Na(+)/K(+)-ATPase and Mg(2+)-ATPase, retained 70-80% activity after the adsorption. In addition, adsorption stabilizes Na(+)/K(+)-ATPase and Mg(2+)-ATPase, since the activities are substantial 3 weeks after the adsorption. Parallel kinetic analysis showed that adsorption does not alter significantly the kinetic properties of Na(+)/K(+)-ATPase and Mg(2+)-ATPase and their sensitivity to and mechanism of Cd(2+)- or Hg(2+)-induced inhibition. The only exception is the "high affinity" Mg(2+)-ATPase moiety, whose affinity for ATP and sensitivity toward Cd(2+) were increased by the adsorption. The results show that such system may be used as a practical and comfortable model for the in vitro toxicological investigations.

Adenosine Triphosphate↗
PubMed2002

Stability of polycarbonate and polystyrene surfaces after hydrophilization with high intensity oxygen RF plasma.

A general drawback observed with plasma treatment is the limited stability of the hydrophilic-treated surfaces toward washing, storage, or heating. It has recently been found that oxygen, air, or argon radiofrequency plasmas with higher intensities than normally used can give hydrophilic surfaces having good wash stability. High intensity oxygen plasma treatment of polystyrene and polycarbonate surfaces was therefore carried out using two different capacitively coupled RF reactors with internal shelf electrodes. The obtained surface characteristics and stability were evaluated using contact angle measurements, XPS, AFM, and nanoindentation. For both materials, low water contact angles were found to correlate with high surface oxygen content. Only the surfaces exposed to relatively intense treatments, with self-bias voltages above 140 V (polystyrene) or 240 V (polycarbonate), could withstand washing in ethanol and remain highly hydrophilic. Substantial amounts of nonsoluble material were observed on the plastic substrates after treatment. Furthermore, for polycarbonate Young's modulus of the surface was found to increase with increasing intensity of the plasma. These observations were taken as an indication that extensive cross-linking of the surface layer took place. After more than 6 months of storage, the samples treated with the most intense plasmas (self-bias voltages in the range of 480-600 V) still had water contact angles around 20 degrees .

Oxygen↗
PubMed1995

A model for estimating the daily dietary intake of a substance from food-contact articles: styrene from polystyrene food-contact polymers.

An approach has been developed to estimate the exposure of consumers to styrene from polystyrene food-contact articles which incorporates published literature on the diffusion of styrene through polymeric materials and industry survey data on uses of polystyrene in food-contact applications. The approach has been shown to be quite practical and has yielded an exposure estimate of 3 ppb (9 micrograms/day) styrene, on average, in the daily diet of people in the United States. This value compares reasonably well with the value of 1-4 micrograms/day for residents of the United Kingdom in 1983. The value is also four orders of magnitude less than the acceptable daily intake calculated by the Styrene Information and Research Center.

Animals↗
PubMed1994

Binding of carbohydrates to solid supports, Part 2: Reaction of sugar hydrazones with isothiocyanate-substituted polystyrene.

The binding of sugars to a polymer support as thiosemicarbazones has been investigated as a means of immobilizing glycans. Hydrazones of glucose and N-acetylglucosamine were prepared by reaction with hydrazine hydrate, and successfully reacted with isothiocyanate-substituted polystyrene by incubation at room temperature and neutral pH. The binding was efficient and stable in aqueous buffers over a range of pH conditions. The bound sugars were recovered in moderate yield by treatment of the beads with hydrazine hydrate, benzaldehyde or acetone. Direct binding of reducing sugars to thiosemicarbazide-substituted polystyrene was not successful because of the unfavourable thermodynamics.

Binding Sites↗
PubMed1996

The impact of polystyrene resins in solid-phase organic synthesis.

A major objective of the DIVERSOMER technology is to provide pure and characterized compounds for biological testing in order to prevent 'false negatives' in our libraries. On several occasions, analysis of the final products by 1H-NMR and MS, has revealed by-products from the polystyrene solid support. Subsequently, three alternative methods were studied to remove polystyrene by-products; (i) prewashing of the resin prior to execution of the synthesis; (ii) pretreatment of the resin with the cleavage conditions consistent with the solid-phase synthesis reaction scheme; and (iii) parallel purification.

Chemistry, Organic↗
PubMed1993

Reduction of potassium in drinks by pre-treatment with calcium polystyrene sulphonate.

Dietary potassium intake in patients with chronic renal failure is generally reduced by oral administration of potassium-binding resins. These drugs may cause disturbances of bowel function and have an unpleasant taste. Pre-treatment of drinks with these resins and their subsequent removal may prevent these inconveniences. In four formulas (whole milk, humanised infant formula, apple juice, and orange juice) we were able to lower the potassium content by 50% with calcium polystyrene sulphonate. No important increase of sodium content was observed, as was reported with the use of sodium polystyrene sulphonate. There was a, potentially beneficial, increase of the calcium concentration.

Beverages↗
PubMed2006

Effect of polystyrene microsphere surface to fluorescence lifetime under two-photon excitation.

Molecular assays such as immunoassays are often performed using solid carriers and fluorescent labels. In such an assay format a question can be raised on how much the fluorescence of the label is influenced by the bio-affinity binding events and the solid carrier surface. Since changes in fluorescence intensity as labels bind to surfaces are notoriously difficult to quantify other approaches are preferred. A good indicator, independent of the fluorescence intensity of the label, is the fluorescence lifetime of the marker fluorophore. Changes in fluorescence lifetime reliably indicate the presence of dynamic quenching, energy transfer or other de-excitation processes. A microsphere based assay system is studied under two-photon excitation. Changes in fluorescence lifetime are studied as labeled protein conjugates bind on microsphere surfaces--both direct on the surface and with a few nanometer distance from the surface. Fluorescence signal is measured from individual polystyrene microspheres and the fluorescence lifetime histogram is simultaneously recorded. The results indicate that self-quenching and quenching by the polystyrene surface are both present in such a system. However, the effect of the surface can be avoided by increasing the distance between the surface and the label. Typical distances achieved by a standard sandwich type of assay, are already sufficient to overcome the surface induced quenching in fluorescence detection.

Animals↗
PubMed2003

Sterile polystyrene culture dishes induce transformation of polyps into medusae in Aurelia aurita (Scyphozoa, Cnidaria).

Polyps of Aurelia aurita produce medusae once a year. Under laboratory conditions this process, termed strobilation, can be induced by lowering the incubation temperature for about two weeks. Here we report a fast induction of strobilation by sterile polystyrene culture dishes. The effect is abolished when the culture dishes are washed twice with hot water prior to the experiment. We recommend that polystyrene cultureware should be pre-washed whenever there is an indication of unusual effects.

Animals↗
PubMed1986

Fluorometric determination of polystyrene latex: application to the measurement of phagosomes and phagocytosis.

Intrinsic fluorescence of polystyrene dissolved in organic solvents such as 1,2-dimethoxyethane was used to develop a sensitive method for the quantification of polystyrene latex beads. This method allows the assay of latex in the microgram range and is one order of magnitude more sensitive than the conventional spectrophotometric method. The fluorometric technique was used in the quantification of phagocytic latex particle uptake by macrophages and in the quantification of isolated phagosomal fractions.

Animals↗
PubMed1986

The influence of radioiodination on the adsorption of IgG and serum albumin to polystyrene.

The adsorption of radioiodinated rabbit IgG and bovine serum albumin (BSA) to polystyrene tubes was investigated. Adsorption isotherms where the proportion of the protein bound was relatively constant over a range of intermediate protein concentrations, and where the proportion bound was protein dependent, were obtained. To investigate the effects of radioiodination, proteins labeled to give a wide range of substitution ratios (0.03 to 3.7 125I/protein molecule) were employed. While labeling did not appear to affect BSA adsorption, the kinetics of IgG binding were altered in a number of ways. The proportion bound in the concentration independent region was decreased even at substitution ratios less than or equal to 0.2. In addition, while all preparations of iodinated BSA, and IgG preparations with less than or equal to 1.6 125I/IgG, gave bimodal adsorption isotherms, with more heavily labeled IgG (greater than or equal to 2.5 125I/IgG) the apparent high affinity binding to the plastic surface was abolished. These results indicate that radioiodination substantially alters the kinetics of the binding of IgG to polystyrene. In addition, the results obtained are discussed with respect to previous relevant and often apparently contradictory findings.

Adsorption↗
PubMed1990

Large-scale purification of synthetic oligonucleotides and carcinogen-modified oligodeoxynucleotides on a reverse-phase polystyrene (PRP-1) column.

A procedure is described for the large-scale purification of synthetic oligonucleotides using a polystyrene (PRP-1, Hamilton Co.) high-performance liquid chromatography (HPLC) column with a phosphate/methanol/acetonitrile solvent system. Pure oligonucleotides are obtained with a three-step procedure that involves only one column purification step. The dimethoxytrityl group is left on the oligomer for the HPLC purification. The use of the PRP-1 polystyrene column with a phosphate/methanol/acetonitrile solvent system provides excellent separation of the desired dimethoxytrityl-bearing oligonucleotide from failure sequences. The dimethoxytrityl group is removed by treatment with acetic acid and the oligonucleotide is desalted on a C-18 Sep-Pak cartridge. The oligodeoxynucleotides obtained are shown to be essentially pure by HPLC, polyacrylamide gel electrophoresis, and 500-MHzNMR spectroscopy. This procedure is especially useful for the large-scale purification of oligonucleotides required for NMR studies. The PRP-1 column and the phosphate/methanol/acetonitrile solvent system is useful for purifying modified oligonucleotides containing lipophilic groups such as the carcinogen 2-(acetylamino)fluorene.

Base Sequence↗
PubMed1988

Antibody immobilization on swollen polystyrene tubes for the radioimmunological determination of total human serum IgE.

A new technique for preparing activated polystyrene tubes was developed involving the controlled swelling of plastic. The quantity of antibodies immobilized on these tubes, and consequently the quantity of bound IgE, was considerably increased. Calibration curves were plotted and the determination of total IgE in 200 serum samples confirmed the expected increase in sensitivity compared to a standard method. The manufacturing procedure was simple and could easily be automated. Thus, swollen polystyrene tubes constitute an advantageous solid stage in the assay of total IgE, which can improve the sensitivity of various radioimmunological determinations.

Antibodies↗
PubMed1977

Polystyrene balls as the solid-phase of a double-antibody radioimmunoassay for human serum albumin.

Polystyrene balls have been incorporated as the solid-phase of a model double-antibody radioimmunoassay for human serum albumin. Purified IgG from the secondary antiserum is adsorbed on the 6.4 mm diameter balls. The solid-phase secondary antibody is then used to separate primary antibody bound iodinated antigen from unbound antigen. The secondary antibody coated polystyrene balls are easily prepared and manipulated; several hundred sample dilutions can readily be processed in a single assay. Assay background values of 1.5% or less are consistently obtained without extensive or special washing procedures.

Animals↗
PubMed1978

Scanning electron microscopic appearance of viral-antigen-coated polystyrene balls.

A radioimmunoassay (RIA) was recently developed for the detection of antiviral IgG and IgM class-specific antibodies using antigen-coated polystyrene balls as the RIA solid-phase. In this communication the attachment and distribution of herpes simplex virus (HSV) capsid and envelope antigens and rubella viruses on the surface of the balls was examined by scanning electron microscopy (SEM). In SEM the surface of the untreated 'clear frosted' polystyrene balls appeared very uneven with innumerable pits and grooves. The viral particles were haphazardly distributed both in the grooves and on the exposed surface of the balls. The strength of adsorption of the viral antigens onto the balls seemed to be remarkably resistant to outside mechanical forces. HSV antigens frequently appeared in clusters, whereas rubella viruses were mostly found as single particles.

Antigens, Viral↗
PubMed1985

Quantitative evaluation of opsonin-independent phagocytosis by alveolar macrophages in monolayer using polystyrene microspheres.

Macrophages can bind and engulf a variety of particles in the absence of specific opsonins. Polystyrene-type microspheres are often employed to quantitate opsonin-independent phagocytic activities of macrophages in vitro. Reliable measurement of this cell function, however, requires the ability of the investigator to distinguish between particles that are merely attached to the cell surface and those that are actually internalized. We have developed a simple, rapid, and reproducible method for quantitating phagocytosis using polystyrene microspheres and adherent alveolar macrophages. Basically, particles associated with macrophages after a given incubation time are microscopically quantitated on a cell-by-cell basis before and after toluene dissolution of external particles. Particle/macrophage values obtained after toluene treatment exclusively index phagocytosis.

Animals↗
PubMed1990

Long term expansion of cytomegalovirus-specific T cell lines in the absence of antigen or antigen-presenting cells. Use of monosized polystyrene particles coated with agonistic antibodies.

Functional and molecular studies of T lymphocytes involved in normal and abnormal immune responses, i.e., cells infiltrating tissues affected by autoimmune processes, require their previous in vitro expansion. Problems such as unavailability of specific antigen(s) and/or the requirement of large amounts of autologous peripheral blood mononuclear cells (PBMNCs) as feeder cells, demand the development of alternative expansion methods. Cytomegalovirus (CMV)-primed PBMNCs from several seropositive subjects were expanded for 5-6 weeks by stimulation with anti-CD3 coated onto polystyrene beads plus interleukin-2 (IL-2) with a similar efficiency than when the MAb was presented by autologous MNCs. Beads coated with anti-CD4, but not with anti-CD8, were also able to maintain the long term growth of CMV-primed populations of T cells. The expanded T cells of one of these polyclonal populations were cloned by limiting dilution using anti-CD3 or CMV, and autologous PBMNCs as stimuli. 16 and 11 clones, respectively, were obtained and grown to several million cells for 1-2 months by weekly stimulations with anti-CD3-coated beads and IL-2. Proliferation assays performed with most of the clones generated with anti-CD3 stimulation showed that all the tested clones had retained the CMV and the class II MHC restriction specificities for at least 3-4 months after the initial CMV stimulation. All the tested clones secreted IL-2 in response to CMV and were CD3+, CD4+ and CD8-. Comparison of the growth of two of these clones by stimulation with: (a) anti-CD3-coated beads and IL-2; (b) anti-CD3, autologous MNCs and IL-2; or (c) CMV, autologous MNCs and IL-2, showed that the first combination was at least as efficient as the other two in expanding these T cell clones. We conclude that polystyrene monosized particles coated with agonistic antibodies can induce the long term growth of antigen-specific T cell lines in the absence of specific antigen and feeder cells, often unavailable specially in the context of human autoimmune studies.

Antibodies, Monoclonal↗