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

The oscillating rheometer is a valuable instrument for studying the effects of additives on the setting behavior of a cement system. Using this instrument, it was found that certain chelating comonomers, the hydroxycarboxylic acids, could improve the setting characteristics of the glass-ionomer cement system when added to the PAA solution. The acid chelates probably assign the extraction of metal ions from the glass and also tend to hold them in solution, preventing premature ion binding of the polyanion chains. The effect is to increase the rate of hardening without reducing the working time, which may indeed by slightly increased. Tartaric acid, the most effective of the comonomers, can form a chelate bridge between aluminum atoms, and this metal complex probably acts as a flexible bridge structure linking polyanion chains. This mechanism offers some steric advantages over a simple salt bridge.
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PMID:Reactions in glass-ionomer cements: IV. Effect of chelating comonomers on setting behavior. 106 62

Nationally synthesized chemopreparations: phosphonoacetic (PAA), phosphonoformic (PFA) acids and acycloguanosine (Acg) exhibit a marked antiherpetic effect in cell cultures and marked protective effect in herpes meningoencephalitis in mice induced by intraperitoneal inoculation of herpes simplex virus type 1 (HSV-1) (43% PFA, 33% PAA, 25% Acg). Both in vitro and in vivo (mouse meningoencephalitis), PFA (its trisodium salt) on the whole proved to be less toxic than PAA but exerted a higher or similar antiherpetic effect. The combined use of pyrophosphate analogues (PAA, PFA) with Acg is more effective that their use separately both in vitro and in herpes meningoencephalitis in mice an produces an additive effect or one similar to it. Systemic inoculation of interferon inducers, lafarine or ridostine, is effective in herpes meningoencephalitis in mice induced by intraperitoneal inoculation of HSV-1 (the protective effect 33% and 26%, respectively). The combined use of ridostine and PAA in herpes meningoencephalitis in mice led to synergistic effect.
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PMID:[Effectiveness of Soviet derivatives of phosphonic acid and their combination with interferon inducers in cell cultures and in a model of herpetic meningoencephalitis in mice]. 255 65

A series of polymeric ophthalmic inserts containing pilocarpine were formulated with four different types of polyvinyl alcohol, PVA, and two types of hydroxypropylcellulose. Pilocarpine was present as the nitrate, or as the salt with polyacrylic acid, PAA. In-vivo miosis vs time experiments on albino rabbits, showed that all inserts increased significantly the bioavailability of pilocarpine, with respect to a standard solution of pilocarpine nitrate. Two PVA inserts, containing the PAA-salt of pilocarpine, were particularly effective. The preparations were also submitted to in-vitro release tests and to differential scanning calorimetry, to ascertain the release mechanism, and to verify, via the thermal behaviour, possible interactions between drug and polymers. The chemical and physiochemical factors, most likely to influence the ophthalmic bioavailability of pilocarpine from the present preparations, are briefly reviewed.
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PMID:Vehicle effects in ophthalmic bioavailability: an evaluation of polymeric inserts containing pilocarpine. 614 68

Ultrafiltration (UF) membranes from polysulfone (PSf) were functionalized by heterogeneous photo-initiated graft copolymerization of acrylic acid (AA). With radiation susceptible PSf, only proper selection of the UV energy (lambda > 350 nm; for selective excitation of the photoinitiator) yielded membranes with preserved UF barrier layer. Possibilities for adjusting structure and morphology of the graft polymer (g-PAA) layer by variation of functionalization parameters such as AA concentration and UV irradiation time were investigated. Very long grafted chains (Mw > 10(5) g mol(-1)) at varied grafting density (GD = 0.01 ... 1.2 nmol cm(-2), relative to the outer surface area) were obtained. Partial penetration of the UF barrier layer by g-PAA was verified. Covalent immobilization of bovine serum albumin (BSA), gamma-globulin (gamma-Gl) and alkaline phosphatase (APh) was achieved by coupling with a water soluble carbodiimide. Bound BSA and gamma-Gl amounts were up to gamma = 10 microg cm(-2), for membranes accessible only from the outer surface thus not using the entire pore volume. Locally addressed covalent protein immobilization after photo-patterning the PSf surface could be visualized with a fluorescent FITC-BSA conjugate. A strong salt effect onto immobilized APh activity (increase with NaCl concentration) was observed, indicating internal transport/accessibility limitations in the g-PAA layer. Correlations between PAA structure (Mw, GD) and accessibility (from BSA or gamma-G1 binding and APh activity) could be established. The 'tentacle' g-PAA functionalized PSf UF membranes having preserved UF barrier and, e.g., with surface-bound receptors will find application in cell cultures under diffusion or perfusion conditions.
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PMID:Ultrafiltration membrane surfaces with grafted polymer 'tentacles': preparation, characterization and application for covalent protein binding. 972 Aug 86

Chitosan/polyacrylic acid I PN's were prepared by radical polymerization of acrylic acid, AA, activated at low temperature, in an aqueous/alcoholic chitosan dispersion. AA monomer to polymer conversion and membrane compositions were determined by elemental analysis and FTIR. Evidences of interpolyelectrolite complex formation were found from the FTIR spectra as well. The gravimetric measurements and the elemental analysis after some exhaustive PAA extraction support the existence of some PAA grafting on the reactive amine group of the chitosan. Swelling degree of the membranes is highly dependent on pH and composition, showing a higher swelling in membranes richer in AA and increased pH due to the breaking of interpolyelectrolite salt bonds.
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PMID:Self-curing membranes of chitosan/PAA IPNs obtained by radical polymerization: preparation, characterization and interpolymer complexation. 1051 63

Interactions between poly(acrylic acid) labeled with pyrene (PAA-Py) and succinylated calfskin collagen (type I) (SCSC) were studied by fluorescence spectroscopy. PAA-Py exhibits a strong emission from pyrene monomer (intensity, I(M)) when it exists in an extended conformation. It exhibits another broad emission from pyrene excimer (intensity, I(E)) when it adopts a collapsed globule conformation. At pH 3, a value that is lower than the isoelectric point of SCSC, the ratio I(E)/I(M) value decreased cooperatively with increasing concentration of SCSC at constant PAA-Py concentration, under salt-free condition. On the other hand, this effect was not observed in the presence of 0.1 M NaCl. At pH 7, a value higher than the isoelectric point of SCSC, the ratio I(E)/I(M) was not affected by the presence of SCSC in the absence and presence of salt. From electrophoretic light scattering experiments, it was found that at pH 3 PAA-Py was negatively charged, while SCSC had a positive charge. Thus it is strongly suggested that the two polymers interact by electrostatic attraction at low pH where they are oppositely charged, and that PAA-Py adopts an extended conformation in the complex formed with SCSC. Similar interactions are believed to occur between dentinal collagen and the polycarboxylate component of glass-ionomer cements.
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PMID:Interaction of water-soluble collagen with poly(acrylic acid). 1065 24

The aim of this work was to evaluate how the addition of mucoadhesive polymers to aqueous solutions affects the ocular response of tropicamide (0.2%; w/v). The polymer solutions tested were carboxymethylcellulose sodium salt (CMC-Na; 1%; w/v), hyaluronic acid sodium salt (HA-Na; 0.1%; w/v) and polyacrylic acid (PAA; 0.2%; w/v). Polymeric solutions were compared to a nonviscous formulation (AS). In vitro mucoadhesion measurements were expressed as a percentage of the adhesion force mucin-mucin, considering this one as 100% mucoadhesion. The values ofmucoadhesion obtained were 172%, 127%, 103% and 87.6% for formulations with CMC, PAA, HA and AS, respectively. The mydriatic response of tropicamide was determined in adult male New Zealand rabbits, weighing 1.7-2 Kg, by pupil diameter measurements at different times after instillation. The area under the mydriatic response-time curve (AUC 0-6 hr) was interpreted as an indication of the bioavailability of tropicamide in each vehicle. The AUC 0-6 hr was related to the in vitro mucoadhesion for each formulation. Tropicamide solutions with CMC-Na and PAA resulted in mucoadhesion and AUC 0-6 hr values approximately 1.9 and 1.4 times higher than AS. Although the solution with HA-Na was less mucoadhesive than PAA, the hyaluronic acid solution resulted in a higher AUC mydriasis/time value. Formulations with HA-Na and PAA presented values of surface tension close to that observed in the lacrimal fluid, with the Imax (maximum pupil diameter) being higher than for CMC-Na and AS. Greater than 90% of the mydriatic effect disappeared 4.5 hr after instillation for PAA and AS. Nevertheless, the mydriatic effect remained up to 5.5 hr for HA-Na and CMC-Na. HA-Na solution enhanced the bioavailability oftropicamide, presenting a value of mucoadhesion similar to the reference mucin-mucin.
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PMID:Enhancement of the mydriatic response to tropicamide by bioadhesive polymers. 1111 33

Non-covalent molecular imprinting of poly(allylamine hydrochloride) (PAA HCl) with glucose phosphate mono-sodium salt produced molecularly imprinted polymer (MIP) hydrogels capable of quantitative, isomerically specific binding of glucose. By ionic association of a template molecule, glucose phosphate mono-sodium salt, to the polymer prior to covalent crosslinking, MIP hydrogels were created with an affinity for binding glucose. In this study we have synthesized MIPs using epichlorohydrin, ethylene glucol diglycidyl ether, and glycerol diglycidyl ether as crosslinkers in order to evaluate their effectiveness with respect to molecular imprinting for glucose. MIP hydrogels were also synthesized with the different crosslinkers and varying amounts of the template molecule in an attempt to elucidate the impact of imprint quantities on the effectiveness of the imprinting technique. Batch equilibration studies, using each of the MIPs and similar non-molecularly imprinted polymers were performed to determine their binding capacities with respect to glucose and fructose. The binding capacity data are discussed and employed in the evaluation of the specificity imparted by the imprinting procedure. MIP hydrogels with binding capacities in excess of 0.5 g of glucose per gram of dried gel were synthesized. Isomeric specificity in hydrogels imprinted for glucose was demonstrated by higher binding capacities of glucose than those of fructose in the same polymers.
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PMID:Molecularly imprinted polymer hydrogels displaying isomerically resolved glucose binding. 1137 47

This paper describes a surface science/mass spectrometry effort to develop and characterize a patterned gold surface that serves as a MALDI sample platform capable of concentrating and purifying proteins. Using microcontact printing, small (200-microm diameter) hydrophilic spots of bare gold or chemically anchored poly(acrylic acid) (PAA) are patterned at 5-mm intervals in a hydrophobic field consisting of a self-assembled monolayer of hexadecanethiol. Building on recent innovations by others, the small hydrophilic spots concentrate the sample to achieve good reproducibility and high sensitivity in the MALDI signal. One of the key features in this work is the combination of the high density of carboxylate groups in PAA with a small spot size to afford both concentration and purification of proteins via ionic interactions. This translates into detection limits for salt-contaminated proteins that are 20-100 times lower (low femtomole) than those reported for previous polymer- or monolayer-modified MALDI probes (using proteins in the 3-15-kDa range). Reflectance FT-IR spectroscopy and ellipsometry were used to determine the amount of protein adsorbed to a PAA-modified sample plate as a function of pH and salt concentration. Amide absorbances in IR spectra correlate well with MALDI-MS signals measured after addition of 2,5-dihydroxybenzoic acid as a matrix.
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PMID:Patterned monolayer/polymer films for analysis of dilute or salt-contaminated protein samples by MALDI-MS. 1255 50

Non-covalent molecular imprinting of poly(allylamine hydrochloride) (PAA.HCl) with D-glucose 6-phosphate monobarium salt (GPS-Ba) produced molecularly imprinted polymer hydrogels (MIP) having an affinity to glucose over fructose. The hydrogels were formed by ionic association of the template molecule, GPS-Ba, to the polymer, prior to covalent crosslinking using epichlorohydrin (EPI). The template was removed by an aqueous base wash. Batch equilibration studies using different MIP hydrogels and non-molecularly imprinted polymers (NIPs) were performed in aqueous and buffered media to determine the binding capacities and isomeric selectivities with respect to the sugars, glucose and fructose. MIP glucose hydrogels exhibited binding capacities in excess of 0.6g of glucose per g of dry gel in a 100% DI H(2)O glucose solution, and in a 50-50% glucose-fructose solution mixture. Equilibrium binding capacities of fructose were lower than those observed with respect to glucose, indicating an isomeric preference for the binding of glucose over fructose. These hydrogels demonstrated a remarkable degree of biomimetic sugar recognition to specifically and selectively bind glucose in their swollen state in environments mimicking physiological conditions.
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PMID:Biomimetic glucose recognition using molecularly imprinted polymer hydrogels. 1473 61


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