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Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have reassessed the effects of CVF administration on the humoral responses to two T-independent immunogens: DNP-Ficoll and DNP-Polyacrylamide. With high immunogen doses, little or no evidence of suppression was found. However, when the immunizing dose was reduced, suppression of both IgG and IgM responses became apparent. As indicated in a previous report, the immunosuppressive effect of CVF on T-dependent responses may result not only from C depletion but also from the generation of C cleavage products that may impair the auxiliary contribution of macrophages to the generation of these humoral responses. A similar mechanism may be applicable to the suppression of antibody production to DNP-Ficoll and DNP-PAA in view of recent reports showing a macrophage requirement for the response to these immunogens.
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PMID:Studies on immunosuppression by cobra venom factor. II. On responses to DNP-Ficoll and DNP-Polyacrylamide. 71 77

Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO.). Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. The spectrum in neutral methanol indicates that it originates from the anionic form -COO(-). Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form -COOH and the cationic form -COOH(2) (+). The ester analogues did not show any changes in various pH conditions. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1'-oxo-2',2',6',6'-tetramethyl-4'-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO.).
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PMID:Preparation and photophysics of 2-(1-pyrenyl)acrylic acid and its methyl and 2',2',6',6'-tetramethyl-4'-piperidyl esters. 1598 51

The salt effect on the complex formation of poly(acrylamide)- block-poly(sodium acrylate) (PAM- b-PAA) as a neutral-anionic block copolymer and dodecyltrimethylammonium bromide (DTAB) as a cationic surfactant at different NaBr concentrations, CNaBr, was investigated by turbidimetric titration, steady-state fluorescence spectroscopy, and dynamic light scattering. At C NaBr < 0.25 M, DTAB molecules may form micelle-like aggregates on PAM- b-PAA chains to form a PAM- b-PAA/DTAB complex above the critical surfactant concentration C critical for the onset of complex formation. In the region of relatively high turbidity, a larger complex is likely to form a core-shell structure, of which the core is a dense and disordered microphase made of surfactant micelles connected by the PAA blocks. The corona was a diffuse shell of PAM chains, and it ensured steric stability. At CNaBr = 0.25 M, a higher electrostatic intermicellar repulsion and intercomplex repulsion induced by a large amount of bound DTAB micelles may lead to a redissolution of large colloidal complexes into intrapolymer complexes. Moreover, a salt-enhancing effect on the complex formation was observed in the PAM- b-PAA/DTAB system; the critical surfactant concentration decreased with increasing salt concentration at CNaBr < 0.10 M. The salt-enhancing effect is due to the larger increase of interaction in comparison to the screening of the interaction.
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PMID:Salt effect on complex formation of neutral/polyelectrolyte block copolymers and oppositely charged surfactants. 1845 24

Polyacrylamide glycoconjugates, Glyc-PAA, having various tags or labels are convenient tools for analysis of cellular lectins. Adaptation of such glycoprobes for flow cytometry allows us to reveal lectins expressed on cell surface and analyze their carbohydrate specificity as well as functionality. Localization of lectins is visualized by labeling of cells with fluorescein-tagged glycoprobes, Glyc-PAA-fluo, in combination with fluorescent microscopy techniques. Additionally, biotinylated glycoprobes can be immobilized on magnetic particles making it possible to separate a cell population according to its carbohydrate-binding profile. Here, we exemplify application of glycoprobes in the study of cellular siglecs and galectins, as well as lectin patterning of tumor cells. The specificity of sialic acid binding membrane-anchored lectins, siglecs-1, -5, -7, -8 and -9 was determined using this methodology. To study the carbohydrate-binding profile of soluble galactoside-binding lectins, galectins-1 or -3, these were loaded on (initially galectin free) Raji cells and probed using Glyc-PAA-fluo. Lessons learned from this model system allowed us to study the galectin distribution pattern of tumors: cells obtained from mice carrying mammary adenocarcinoma or lymphoma were probed with Glyc-PAA-fluo using flow cytometry. Disaccharide 6OSuLacdiNAc was shown to be the most potent probe for adenocarcinoma cells, demonstrating that 6OSuLacdiNAc-binding molecules accumulate on cell surface in a patch-wise distribution.
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PMID:Glycoprobes as a tool for the study of lectins expressed on tumor cells. 1928 39

Currently, research is focused on the synthesis of new composite coagulants, which are constituted of both inorganic and organic materials. In this paper, the development of relevant reagents was investigated, by combining the inorganic pre-polymerised iron-based coagulant Polyferric Sulphate (PFS) with an organic, non-ionic polymer (Polyacrylamide, PAA) under different PAA/Fe (mg/l) and OH/Fe molar ratios. Moreover, the new reagents were characterised in terms of typical properties, stability and morphological analysis (XRD, FTIR, SEM). Their coagulation performance, when treating low or high turbid kaolin-humic acid suspensions, was also investigated, whereas the applied coagulation mechanisms were discussed by using the Photometric Dispersion Analysis (PDA) analysis. The results show that the new coagulation reagents present improved properties, including increased effective polymer species concentration, and they exhibit very good stability. The respective tests using PDA confirmed that the predominant coagulation mechanism of PFS-PAA is the bridge formation mechanism. Coagulation experiments in low or high turbid kaolin-humic acid suspensions reveal that the novel composite reagent PFS-PAA exhibits better coagulation performance, when compared with simple PFS, in terms of zeta-potential reduction, turbidity and organic matter removal and residual iron concentration.
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PMID:A new inorganic-organic composite coagulant, consisting of polyferric sulphate (PFS) and polyacrylamide (PAA). 1956 Jan 80

In this article, we demonstrate that by tethering carboxyl groups of poly(10,12-pentacosadiynoic acid) (PDA) to a poly(vinyl alcohol) (PVA) matrix, PDA, which is irreversible in its pure form, becomes reversible in the thermochromism. The tethering is realized by simple but deliberately designed processes: (1) Disperse the commercially available monomer 10,12-pentacosadiynoic acid (DA) nanocrystals in a PVA aqueous solution by the "NCCM" method invented in our laboratory. (2) Anneal and dry the mixture solution at a temperature higher than the melting point of pure DA crystal. (3) Polymerize the as-annealed DA/PVA blend films by UV irradiation. After the polymerization, PDA/PVA films with completely reversible thermochromism are obtained. The reversible PDA/PVA films can be easily dissolved in water, leading to water-dispersible nanoaggregates with the reversibility. Blends of PDA with other water-soluble polymers such as poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA) and poly(allyamine) (PAM), were prepared respectively, by the same processes and under the same conditions. It is found that all these nanocomposites are irreversible or partially reversible in the thermochromism; either the relatively low glassy transition temperature of the polymer matrix (in the case of PEO) or the partial ionization nature of the polymer (in the cases of PAA and PAM) is responsible for the irreversibility or the partial reversibility.
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PMID:Deliberately designed processes to physically tether the carboxyl groups of poly(pentacosadiynoic acid) to a poly(vinyl alcohol) glassy matrix to make poly(pentacosadiynoic acid) thermochromically reversible in the matrix. 2156 53

The salt effect on complex formation of poly(acrylamide)-block-poly(acrylic acid) (PAM-b-PAA) and dodecyltrimethylammonium bromide (DTAB) at different NaBr concentrations, C(NaBr), was investigated by laser light scattering (LLS) and small angle neutron scattering (SANS). LLS and SANS clearly indicates that the aqueous solution of PAM-b-PAA and DTAB associate into colloidal complexes. For low surfactant-to-polymer charge ratio Z lower than the critical value Z(C), the colloidal complexes are single DTAB micelles dressed by a few PAM-b-PAA. Above Z(C), the colloidal complexes form a core-shell microstructure. The complex formation in the PAM-b-PAA/DTAB is enhanced by addition of salt: Z(C) decreases with increasing C(NaBr). This is considered to similar to the cmc behavior for the pure surfactant system. The core of the complex consists of densely packed surfactant micelles (DTA(+)), and PAA block chains bind to these micelles, displace their counteranions (Br-) and bridge them. The corona of the complex is constituted from the PAM. Since the interaction between polyelectrolyte and oppositely charged surfactant is primarily electrostatic in nature, the core radius and the intermicellar distance of the DTA(+) micelles inside the core depend on C(NaBr). The addition of salt screens the electrostatic attraction between oppositely charged PAA block and DTAB, which weakens the interaction. With increasing C(NaBr), therefore, the core of the colloidal complex is considered to swell, which leads to the increases in the core radius R(C) and the intermicellar distance of the DTA(+) micelles inside the core. The aggregation number expressed in terms of DTA(+) micelles per complex is also evaluated using the analogy with the homopolyelectrolyte/surfactant system.
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PMID:Salt effect on microscopic structure and stability of colloidal complex obtained from neutral/polyelectrolyte block copolymer and oppositely charged surfactant. 2219 35

Hybrid polyion complex (HPIC) micelles are nanoaggregates obtained by complexation of multivalent metal ions by double hydrophilic block copolymers (DHBC). Solutions of DHBC such as the poly(acrylic acid)-block-poly(acrylamide) (PAA-b-PAM) or poly(acrylic acid)-block-poly(2-hydroxyethylacrylate) (PAA-b-PHEA), constituted of an ionizable complexing block and a neutral stabilizing block, were mixed with solutions of metal ions, which are either monoatomic ions or metal polycations, such as Al(3+), La(3+), or Al(13)(7+). The physicochemical properties of the HPIC micelles were investigated by small angle neutron scattering (SANS) and dynamic light scattering (DLS) as a function of the polymer block lengths and the nature of the cation. Mixtures of metal cations and asymmetric block copolymers with a complexing block smaller than the stabilizing block lead to the formation of stable colloidal HPIC micelles. The hydrodynamic radius of the HPIC micelles varies with the polymer molecular weight as M(0.6). In addition, the variation of R(h) of the HPIC micelle is stronger when the complexing block length is increased than when the neutral block length is increased. R(h) is highly sensitive to the polymer asymmetry degree (block weight ratio), and this is even more true when the polymer asymmetry degree goes down to values close to 3. SANS experiments reveal that HPIC micelles exhibit a well-defined core-corona nanostructure; the core is formed by the insoluble dense poly(acrylate)/metal cation complex, and the diffuse corona is constituted of swollen neutral polymer chains. The scattering curves were modeled by an analytical function of the form factor; the fitting parameters of the Pedersen's model provide information on the core size, the corona thickness, and the aggregation number of the micelles. For a given metal ion, the micelle core radius increases as the PAA block length. The radius of gyration of the micelle is very close to the value of the core radius, while it varies very weakly with the neutral block length. Nevertheless, the radius of gyration of the micelle is highly dependent on the asymmetry degree of the polymer: if the neutral block length increases in a large extent, the micelle radius of gyration decreases due to a decrease of the micelle aggregation number. The variation of the R(g)/R(h) ratio as a function of the polymer block lengths confirms the nanostructure associating a dense spherical core and a diffuse corona. Finally, the high stability of HPIC micelles with increasing concentration is the result of the nature of the coordination complex bonds in the micelle core.
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PMID:Hybrid polyion complex micelles formed from double hydrophilic block copolymers and multivalent metal ions: size control and nanostructure. 2224 9

Magnetite nanoparticles (MNPs) coated with poly(acrylic acid-co-maleic acid) polyelectrolyte (PAM) have been prepared with the aim of improving colloidal stability of core-shell nanoparticles for biomedical applications and enhancing the durability of the coating shells. FTIR-ATR measurements reveal two types of interaction of PAM with MNPs: hydrogen bonding and inner-sphere metal-carboxylate complex formation. The mechanism of the latter is ligand exchange between uncharged -OH groups of the surface and -COO(-) anionic moieties of the polyelectrolyte as revealed by adsorption and electrokinetic experiments. The aqueous dispersion of PAM@MNP particles (magnetic fluids - MFs) tolerates physiological salt concentration at composition corresponding to the plateau of the high-affinity adsorption isotherm. The plateau is reached at small amount of added PAM and at low concentration of nonadsorbed PAM, making PAM highly efficient for coating MNPs. The adsorbed PAM layer is not desorbed during dilution. The performance of the PAM shell is superior to that of poly(acrylic acid) (PAA), often used in biocompatible MFs. This is explained by the different adsorption mechanisms; metal-carboxylate cannot form in the case of PAA. Molecular-level understanding of the protective shell formation on MNPs presented here improves fundamentally the colloidal techniques used in core-shell nanoparticle production for nanotechnology applications.
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PMID:Designed polyelectrolyte shell on magnetite nanocore for dilution-resistant biocompatible magnetic fluids. 2314 Feb 79

We previously reported that the stability and aqueous catalytic activity of met-hemoglobin (Hb) was improved when covalently conjugated with poly(acrylic acid) (PAA). In the current study, the Hb-PAA-water interface was modified to improve Hb catalytic efficiency in organic solvents (0-80% v/v organic solvent; remainder is the conjugate, the substrate, and water). The protein-polymer-solvent interface modification was achieved by esterifying the carboxylic acid groups of Hb-PAA with ethanol (EtOH) or 1-propanol (1-prop) after activation with carbodiimide. The resulting esters (Hb-PAA-Eth and Hb-PAA-1-prop, respectively) showed high peroxidase-like catalytic activities in acetonitrile (ACN), dimethylformamide (DMF), EtOH, and methanol (MeOH). Catalytic activities depended on the log(P) values of the solvents, which is a measure of solvent lipophilicity. The highest weighted-average activities were noted in MeOH for all three conjugates, and the lowest average activities were noted in DMF for two of the conjugates. Interestingly, the average activities of the conjugates were higher than that of Hb in all solvents except in ACN. The ratio of the catalytic rate constant (kcat) to the Michaelis constant (KM), the catalytic efficiency, for Hb-PAA-Eth in MeOH was the highest noted, and it is ~3-fold higher than that of Hb in buffer; conjugates offered higher efficiencies than Hb at most solvent compositions. This is the very first general, versatile, modular strategy of coupling the enhanced stability of Hb with improved activity in organic solvents via the chemical manipulation of the polymer shell around Hb and provides a robust approach to efficient biocatalysis in organic solvents.
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PMID:Efficient biocatalysis in organic media with hemoglobin and poly(acrylic acid) nanogels. 2478 34


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