Reactive Block Research Articles

New Reactive Block Copolymers as Stabilizers in Emulsion Polymerization

The synthesis and application of partly sulfonated polybutadiene-block-poly(ethylene glycol) copolymers as a new class of stabilizers for emulsion polymerizations is reported. These stabilizers combine all known stabilization mechanisms - electrostatic, steric, and electrosteric - together with the ability to participate in radical polymerization in a single molecule. It was found that the kind of initiator has a strong influence on the latex properties. Due to the polyelectrolyte nature of the new stabilizers, nonionic water-soluble poly(ethylene glycol) azo-initiators lead to smaller particles and less coagulum compared to water-soluble ionic initiators. The investigations surprisingly revealed that the poly(ethylene glycol)- azo-initiators accumulate in the small-particle-size fraction due to side reactions leading to their incorporation. The efficiency of the new stabilizers in a radical emulsion polymerization of styrene is highest if the degree of sulfonation is between 20 and 40%. Compared to low molecular weight stabilizers like sodium dodecylsulfate, the reactive block copolymer stabilizers are much more efficient especially at stabilizer concentrations below 0.1% relative to the mass of monomer. The almost complete covalent binding of the reactive polymeric stabilizers to the particles is proved by a combination of ultrafiltration, elemental analysis, GPC, and FT-IR investigations.

Novel Gemini-Type Reactive Dispersants Based on PS/PEO Block Copolymers: Synthesis and Application

In this paper, the possibilities offered by anionic polymerization were exploited to engineer well-defined PS-b-PEO2 gemini-type dispersants that were fitted with terminal styrenic groups. Two routes were explored to obtain this novel generation of surfactants whose thorough characterization indicated that they exhibit the expected molecular structure. These reactive block copolymers have been subsequently used as surfactants in the emulsion polymerization of styrene to stabilize the colloidal particles formed. The kinetics of polymerization in the presence of such reactive surfactants were shown to differ from the case involving PS-b-PEO linear macromonomers as surfactants.

Soluble liver antigen: isolation of a 35-kd recombinant protein (SLA-p35) specifically recognizing sera from patients with autoimmune hepatitis.

Autoantibodies to soluble liver antigen (SLA) are considered a specific marker of autoimmune hepatitis. We have performed immunoscreening of a human liver gene expression library with an anti-SLA-positive serum. A reactive clone with a 35-kd open reading frame (ORF) and a 563 base pair (bp) 3' untranslated region (UTR) was isolated (soluble liver antigen [SLA]-p35), showing strong homology to an independently isolated putative SLA/liver-pancreas antigen (LP) sequence (Acc. No. AF146396), and a UGA serine tRNA-protein complex (tRNP)((Ser) Sec) related protein (AJ238617), as well as different expression sequence tag (EST)-clones from lymphatic and oncofetal tissues. Expressed in Escherichia coli, SLA-p35 showed dose-dependent and complete blocking of reactivity to native SLA antigen after preabsorption with the 35-kd recombinant protein. It recognized 67/85 (78.8%) precharacterized anti-SLA-positive sera in dilutions up to 1:40,000 in immunoblot, without detectable cross reactivity in the controls. The commercially available SLA/LP enzymelinked immunosorbent assay (ELISA), by comparison, recognized 63/85 samples (74.1%). Of the negative samples, 18% showed strong inhibition rates (80% and above) in the polyclonal inhibition ELISA. We conlude that the complementary DNA now isolated by 3 independent approaches encodes for the major but not sole antigenic component of soluble liver antigen. Although its truncated form presented here may serve to improve diagnostics based on the new recombinant polypeptide, it currently cannot fully replace the polyclonal inhibition ELISA.

ChemInform Abstract: Synthesis of 5′-C- and 2′-O-(Bromoalkyl)-Substituted Ribonucleoside Phosphoramidites for the Post-Synthetic Functionalization of Oligonucleotides on Solid Support.

The prepn. of building blocks for the incorporation of 6'-O-(5-bromopentyl)-substituted b-D-allofuranosylnucleosides and 2'-O-[(3-bromopropoxy)methyl]-substituted ribonucleosides into oligonucleotide sequences is presented. These reactive building blocks can be modified with a variety of soft nucleophiles while the (fully protected) sequence is still attached to the solid support. As an example of this strategy, we carried out some preliminary solid-phase substitution and conjugation reactions with DNA sequences contg. a 2'-O-[(3-bromopropoxy)methyl]-substituted ribonucleoside and detd. the pairing properties of duplexes obtained therefrom. [on SciFinder (R)]

Two-dimensional electrophoretic and immunoblot analysis of cell surface proteins of spiral-shaped and coccoid forms of Helicobacter pylori

Cell surface proteins of the human gastric pathogen Helicobacter pylori extracted during different in vitro growth phases were analyzed by one- and two-dimensional gelelectrophoresis (1-DE and 2-DE) and by 2-DE immunoblot. Broth-cultured H. pylori cells were stained with an acridine-orange dye to monitor the morphological status of the organism. In 2-day-cultures, 96% of the bacterial cells were spiral-shaped and four days later a morphological switch to coccoid forms occurred. In 10-day cultures spiral-shaped forms were not found. By 1-DE, proteins with the molecular masses of 87 and 120 kDa were detected in the 2-day cultures that disappeared in cells of 12-day cultures. A protein corresponding in size to the heat shock protein (GroEl homolog, Hsp60) and a 62 kDa protein, the ureaseB-subunit, were identified in extracted proteins of 2-, 8-, and 12-day cultures. 2-DE revealed an increased a number of silver-stained spots of 8-day cultures (in average 250 spots) compared with protein extracted from 2-day cells (in average 160 spots). 2-DE immunoblots performed with sera containing antibodies to major H. pylori proteins such as the A- and B-subunits of urease and the Hsp60 showed similar reactivity to surface proteins extracted from 2-, 8-, and 12-day cultures, suggesting that these proteins remain immunologically intact. Pooled sera from infected patients absorbed with spiral-shaped cells showed an almost total blocking of the antibody reactivity to extracted coccoid proteins in 2-DE immunoblot. Eighteen spots were still visible, but this reactivity probably represents a solid overexpression by the coccoid cells of Hsp60 and ureaseB proteins and is thus difficult to block.

ChemInform Abstract: A Symmetrical Tetrasulfolenoporphyrin as Reactive Building Block.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

New mechanism for dislocation blocking in strained layer epitaxial growth

Dislocation interactions play a critical role in plasticity and heteroepitaxial strain relaxation. We use real time transmission electron microscopy observations of the interaction between threading and misfit dislocations in SiGe heterostructures to investigate interactions quantitatively. In addition to the expected long-range blocking of threading segments, we observe a new short-range mechanism which is significantly more effective. Simulations show that this reactive blocking occurs when two dislocations with the same Burgers vector reconnect.

Selective Grafting of Block Copolymers

Synthesis of nonpolar block copolymers selectively grafted in one block with 4-methylstyrene is described, using a novel two-step method: (i) multisite metalation of the more reactive block by a superbase, prepared from 3-(lithiomethyl)heptane and potassium tert-pentoxide, and (ii) use of the metalated intermediate as a multifunctional initiator for anionic “grafting from” 4-methylstyrene. Various degrees of grafting (up to ca. 50%) were obtained in the reactive block. Also, other characteristics of the grafted block copolymers may be changed in a wide range, such as type and length of starting blocks or structure and length of the introduced grafts. Thus, a great variety of polymeric structures is available by this method. Molecular weight, molecular weight distribution, and molecular size of the copolymers in tetrahydrofuran were determined by static and dynamic light scattering and by size exclusion chromatography coupled with concentration (RI and UV), viscosity, and light scattering detectors.

Comparison of a general model with a simplified approach for the transformation of solid-gas media used in chemical heat transformers

The influence of mass transfer has drawn great attention in the study of gas-solid reversible reactions. Experiments have been conducted for the IMPEX blocks (Mauran et al., 1991, patent no. 91 0303) in reaction with ammonia at low pressure when the influence of mass transfer is significant (Prades, 1992, Thèse de doctorat, Université de Perpignan; Lu et al., 1996b, A.I.Ch.E. J., to be submitted). A general gas-solid reaction model has been developed (Lu et al., 1996a, Chemical Engineering Science 51, 3829–3845) to quantify the non-negligible influence of mass transfer on the global transformation of the reactive media (especially for the cases of less-permeable material). Two levels of coupling have been considered. Firstly, at the grain level, mass transfer and chemical kinetics are coupled, and secondly, at the pellet level, heat transfer and mass transfer are coupled. The simulation results of the general model have revealed that in the process of reaction, there exist two progressive reactive fronts in the pellet, one is the ‘heat front’ moving from the heat exchanger to the gas diffuser and the other is the ‘mass front’, moving from the gas diffuser to the heat exchanger. In this paper, a simplified approach has been made by simplifying the progressive reactive fronts shown in the general model as ‘sharp’ reactive fronts. This simplified approach does not enter into the details at the grain level and does not have the accumulative terms in the model equations. Therefore, it has significantly simplified the numerical calculation. The comparison has shown similarities between the results of these two models, regarding the global advancement and local profiles. If the physical characteristics of the reactive block are constant in the process of the reaction, the simplified model has confirmed to be basically reliable to predict the gas-solid reversible reaction and therefore will serve as an efficient tool for the optimal sizing of a chemical heat transformer. In any other cases, the general model should be used.

Reactivation of thymidine kinase-defective herpes simplex virus is enhanced by nucleoside.

Herpes simplex virus (HSV) mutants defective for thymidine kinase expression (TK-) have been reported to establish latent infection of sensory ganglia of mice, in that HSV latency-associated transcript is expressed, but to be defective for reactivation. In the present study, the mechanism of defective reactivation by TK- HSV was investigated. Latent infection established by each of three reactivation-defective HSV type 1 mutants was studied. Reactivation in explant culture was markedly enhanced by the addition of thymidine (dTdR) to the explant culture medium. Without added dTdR, reactivation occurred in 0 of 32 ganglia, while when dTdR (200 microM) was present, reactivation occurred in 32 of 37 ganglia (86%). Reactivation was minimal or did not occur after treatment with other nucleosides; specificity for dTdR would suggest the importance of dTdR nucleotide levels rather than more general nucleotide pool imbalance. Enhanced reactivation by dTdR was dose dependent and was blocked by acyclovir. While some degree of inhibition of TK- HSV by acyclovir may be expected, the complete block of dTdR-enhanced reactivation was unexpected. This result may suggest that HSV is particularly vulnerable during initial reactivation events. The mechanism of dTdR-enhanced reactivation of TK- HSV was further evaluated during in vivo infection by TK- HSV. For mice infected with TK- HSV, virus was undetectable in ganglia 3 days later. However, for mice infected with TK- HSV and treated with dTdR, virus was readily detected (2.8 x 10(3) PFU per ganglion). This result suggested that in vivo treatment with dTdR enhanced replication of TK- HSV in ganglion neurons. In turn, this suggests that in latently infected ganglia, dTdR-enhanced reactivation of TK- HSV occurred as a result of viral replication in neurons following initial reactivation events.

Molecular mapping of a pathogenically relevant BP180 epitope associated with experimentally induced murine bullous pemphigoid.

Bullous pemphigoid (BP) and herpes gestationis (HG) are subepidermal blistering diseases associated with an autoimmune response directed against BP180, an epidermal hemidesmosomal glycoprotein. The pathogenic relevance of this Ag/Ab system was established by the recent demonstration that IgG Abs reactive with the murine form of BP180 (mBP180) are capable of triggering a subepidermal blistering disease after passive transfer into neonatal BALB/c mice. The aim of the present study was to determine the fine specificity of the pathogenically relevant Abs in this experimental model of BP. Four high titer rabbit-anti-mBP180 antisera were included in this analysis--only two of which exhibited pathogenic activity in the passive transfer model. Immunoblot analysis using a panel of mBP180 deletion mutants revealed that each of the four rabbit sera reacted with at least three distinct sites on the mBP180 ectodomain; however, this technique failed to distinguish between the reactivity patterns of the pathogenic and nonpathogenic sera. An alternative technique, liquid phase immunoadsorption analysis, was used to identify one mBP180 antigenic site, comprising 9 to 12 amino acids and designated mBP1, that was specifically recognized by the two pathogenic sera. Pre-adsorption of pathogenically active IgG preparations with fusion proteins containing the mBP1 antigenic site resulted in complete blocking of immunofluorescence reactivity with the murine basement membrane zone (BMZ) and in complete neutralization of pathogenic activity. Anti-BMZ reactivity displayed by nonpathogenic Abs was not altered or diminished by pre-adsorption with this same mBP180 recombinant protein. These findings should help to elucidate the immunopathologic mechanisms responsible for human BP and HG and may have significant implications in the diagnosis and treatment of these autoimmune diseases.

Physical mapping across the fragile X: Hypermethylation and clinical expression of the fragile X syndrome

The most common genetic cause of mental retardation after Down's syndrome, the fragile X syndrome, is associated with the occurrence of a fragile site at Xq27.3. This X-linked disease is intriguing because transmission can occur through phenotypically normal males. Theories to explain this unusual phenomenon include genomic rearrangements and methylation changes associated with a local block of reactivation of the X chromosome. Using microdisected markers close to the fragile site, we have been able to test these hypotheses. We present evidence for the association of methylation with the expression of the disease. However, there is no simple relationship between the degree of methylation and either the level of expression of the fragile site or the severity of the clinical phenotype.

Effect of a reactive styrene-butadiene block copolymer on some mechanical properties of fibreglass reinforced composites

Effect of a reactive styrene-butadiene block copolymer on some mechanical properties of fibreglass reinforced composites

Molecular design of multicomponent polymer systems. XVI. Emulsification of polystyrene and nylon-6 by a reactive block copolymer

Journal of Polymer Science Part C: Polymer LettersVolume 27, Issue 12 p. 481-488 Article Molecular design of multicomponent polymer systems. XVI. Emulsification of polystyrene and nylon-6 by a reactive block copolymer R. Fayt, R. Fayt Laboratory of Macromolecular Chemistry and Organic Catalysis, University of Lièe, Sart Tilman, B6, 4000 Lièe, BelgiumSearch for more papers by this authorPh. Teyssié, Ph. Teyssié Laboratory of Macromolecular Chemistry and Organic Catalysis, University of Lièe, Sart Tilman, B6, 4000 Lièe, BelgiumSearch for more papers by this author R. Fayt, R. Fayt Laboratory of Macromolecular Chemistry and Organic Catalysis, University of Lièe, Sart Tilman, B6, 4000 Lièe, BelgiumSearch for more papers by this authorPh. Teyssié, Ph. Teyssié Laboratory of Macromolecular Chemistry and Organic Catalysis, University of Lièe, Sart Tilman, B6, 4000 Lièe, BelgiumSearch for more papers by this author First published: November 1989 https://doi.org/10.1002/pol.1989.140271203Citations: 11AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume27, Issue12November 1989Pages 481-488 RelatedInformation

Effect of butyric acid on the germination of the seeds ofPhacelia tanacetifolia

The effect of a weak acid (butyric acid) on the germination of seeds ofPhacelia tanacetifoliaBenth. (cv. Bleu Clair) has been studied. Butyric acid inhibited the early phase of germination, and the inhibition was correlated to the amount of the per‐meant undissociated form present in the incubation medium. The inhibition by butyric acid in the dark was also correlated to a decrease of dark fixation of CO2and to a more pronounced decrease in malic acid levels during the early phase of germination; suggesting that the uptake of the uncharged form of this weak acid was followed by a release of H+ into the cytoplasm, leading to a decrease in its pH. The inhibitory effect of butyric acid in the dark on many metabolic events (rise in respiratory activity, levels of reducing sugars, glucose‐6–phosphate and malic acid, dark CO2fixation, transport activities and macromolecular synthesis) appeared similar to the one of light. Fusicoccin (FC), which directly stimulates the H+pump at the plasmalemma level, ameliorated the effect of butyric acid, as well as that of light, on germination. The bulk of these data is interpreted as suggesting that the mechanism of light inhibition of germination ofPhacelia tanacetifoliaseeds might be the consequence of a general block of metabolic reactivation due to the presence of an unfavourable (acidic) cytoplasmic pH; which might be explained with the lack of the phytochrome‐dependent activation of the H+pump at the plasmalemma level.

Evidence for a regulatory role of the T8 (CD8) antigen in antigen‐specific and anti‐T3‐(CD3)‐induced lytic activity of allospecific cytotoxic T lymphocyte clones

The functional role of the T8 antigen of human T cells was studied by inhibition with anti-T8 monoclonal antibodies (mAb) of the cytotoxic action of T8+ cytotoxic T lymphocyte clones (CTL). All clones were allospecific and directed against HLA-B7. The ability of seven different anti-T8 mAb to inhibit the cytotoxicity of these alloreactive CTL clones corresponded with their avidity for a particular target cell. The lysis of cross-reactive antigen-bearing target cells was more readily blocked by anti-T8 mAb than lysis of the specific B7 target cell against which a clone was raised. The seven anti-T8 mAb showed a spectrum of CTL blocking ability ranging from strong blocking with all five CTL clones tested to weak inhibition of only two out of five clones. mAb inhibition of CTL reactivity and cold target inhibition studies with one of the five CTL clones indicate a post-binding role of the T8 molecule. Functional epitope mapping based on CTL blocking with the anti-T8 mAb resulted in the definition of one nonfunctional epitope on the T8 molecule which is only expressed on mature T lymphocytes and a cluster of closely related functional epitopes expressed on both thymocytes and mature T lymphocytes. Not only allospecific cytotoxicity, but also nonspecific cytotoxicity induced anti-T3 mAb in these allospecific clones was inhibited by anti-T8 mAb in the absence of HLA class I expression on the target cell (Daudi cell line). The hierarchy of blocking with anti-T8 mAb and the classification of functional epitopes on T8 in anti-T3-induced nonspecific cytotoxicity were similar to those obtained in blocking of allospecific reactivity of the CTL clones. This analogy points to an identical function of the T8 antigen in both allospecific and anti-T3-induced nonspecific cytotoxicity. If HLA class I molecules are the counter structures of the T8 antigen, then these results argue against an adhesion-like function of the T8 structure. The combined results show that the T8 molecule has a regulatory role in CTL activation. It is postulated that the T8 antigen might serve as a receptor that transduces a negative feedback signal for T cell activation which prevents T cell triggering by nonspecific interaction.

Biotin-avidin-amplified enzyme immunoassay for detection of herpes simplex virus antigen in clinical specimens.

A biotin-avidin-amplified enzyme-linked immunosorbent assay (B-A ELISA) has been developed to detect herpes simplex virus type 1 (HSV-1) and HSV-2 antigens in clinical specimens. The test was designed as a solid-phase, double-antibody, sandwich assay in which plates were coated with a polyclonal rabbit immunoglobulin G anti-HSV reagent, and the sandwich antibody was a biotin-labeled mouse immunoglobulin M monoclonal antibody that reacts with a common antigen associated with HSV-1 and HSV-2. The test can be completed in 4 h if antibody-coated plates are available. The detection limit of the B-A ELISA, determined by titration of virus stocks, was found to be approximately 90 PFU or 6 X 10(3) physical particles of either HSV-1 or HSV-2 per 50 microliter of virus stock. The following results were obtained in a study in which swabs were taken from a variety of lesions and assayed for infectivity in tissue culture and by B-A ELISA. Of 421 suspected HSV lesions tested, 69 were positive by both tests and 159 were negative by both tests. A total of 122 were positive by B-A ELISA but negative for infectivity. Seventy-one were negative by B-A ELISA but contained infectious virus. The HSV specificity of the assay was substantiated by partial blocking of reactivity with rabbit immunoglobulin G anti-HSV and by the absence of reactivity with a nonspecific biotin-labeled mouse immunoglobulin M monoclonal antibody.

Naturally occurring lymphocyte-mediated immunity to endogenous type-C virus in the mouse. Blocking of the lymphocyte reactivity with antisera to the virus.

The natural immune response in mice to their endogenous type-C viruses involves a complex interaction between cellular and humoral immune mechanisms. The virus-specific immune reactivities are a function of age and appear only subsequent to endogenous virus expression. Cellular immune activity was found to reside in a population of lymphocytes that were characterized as natural killer cells based on their absence of theta surface antigens or immunoglobulin or complement receptors. Cellular and humoral virus-specific immune responses co-occur in the same animal and pretreatment of virus-positive target cells with sera from virus-positive aging mice is capable of partially blocking the cytotoxic activity of reactive lymphocytes. The blocking activity of sera from individual mice increases as a function of age and endogenous virus expression and is highly correlated with the virus-specific complement-dependent cytotoxic activity of these sera. Mouse sera, whether naturally immune or immune as a result of hyperimmunization with type-C virus, exhibit blocking activity that can be removed by absorption with purified type-C virus or purified viral glycoprotein (gp 70) but not by absorption with noninfected syngeneic cells. High-titered and highly specific antisera directed against certain individual R-MuLV structural proteins reveal blocking activity. Monospecific antisera to gp 70 and p 12 exhibited high-titered blocking reactivities which are absorbable by the respective purified proteins. Blocking activity of antisera directed against other viral structural proteins could not be excluded with certainty. These findings raise the possibility that immunity in the mouse to endogenous type-C virus or virus-infected cells involves competition between serum-blocking activity and natural-killer cell activity and further provides a unique model system for studying the mechanism of action of blocking antisera known to have monospecific reactivity against defined and purifiable transplantation antigens.

In Vitro Immune Stimulation-Inhibition to Spontaneous Canine Tumors of Various Histologic Types

Abstract Utilizing dogs with progressively growing tumors we are reporting on the in vitro reactivity of their lymph node or peripheral blood lymphocytes to their own tumor cells. Tumors, lymph nodes, and blood were collected aseptically during surgical treatment or before necropsy. Primary cultures were set up and shortly thereafter only viable glass-adhering tumor cells were utilized. The cells were first incubated with either media or various sera and then varying numbers of sensitized lymphocytes were added. The mixtures were incubated for 90 min in rotating test tubes and then plated into culture dishes or plates. Two and/or 5 days later, the cultures were fixed, stained, and viable target cells were counted. In vitro tumor cell destruction by high numbers of lymphocytes from dogs bearing tumors and the blocking of such reactivity by autologous serum were demonstrated. Serum from dogs with the same histologic type of neoplasm inhibited allogenic lymphocyte cytotoxicity, whereas serum from dogs with a different tumor, normal dogs, and a dog who had been clinically free of osteosarcoma after limb amputation 17 months earlier, did not significantly block the cellular-mediated reactivity. Stimulation of tumor growth in vitro by low ratios of sensitized lymphocytes to tumor cells was demonstrable. Autologous serum from dogs with progressively growing neoplasms appeared to potentiate the stimulation of tumor growth above a simple blocking of lymphocytic-mediated cytotoxicity. These results confirm our earlier reports of immune stimulation to tumor growth in vitro and support the hypothesis and work by Prehn that the early immune response to neoplasia might directly stimulate rather than inhibit tumor growth.

Carbohydrate-rich compounds in the colonic mucosa of man. 3. A preliminary report of some biochemical characteristics of the carbohydrate-rich components in normal colonic mucosa.

Preparations of human colonic epithelial cells were obtained virtually free from contamination by connective tissue. A trichloroacetic acid-soluble carbohydrate-rich fraction was prepared after defatting, proteolytic digestion and trichloroacetic acid precipitation of proteins by precipitating the polysaccharides with ethanol and potassium acetate. Four components of acid mucosubstances were revealed on electrophoresis, three of them showing the presence of sulphate radicals. The periodate consumption rate of the preparation was over four times greater after methanolytic desulphation, and confirms previous results concerning the blocking of periodate reactivity by acid radicals. The analysis of the sample showed the presence of 15% protein, 14% hexose, 9% sialic acid, 6% hexosamine, 3% fucose and 3% uronic acid.