Presence Of PAA Research Articles

SYNTHESIS, CHARACTERIZATION, AND PERFORMANCE OF SULFONATED POLYETHERSULFONE NANOFILTRATION MEMBRANES

ABSTRACT TGA/DTA data. Membranes were prepared from sulfonated polymer and performance characteristics in terms of permeate flux and solute separation are reported. The effects of the casting solution composition on performance of both PES & SPES membranes, effect of feed concentration and separation of different inorganic salts are also included. Separation of multivalent cation (Ca2+) was studied in presence of PAA of different concentration and as a function of pH.

Oxidation of ethylene catalyzed by colloidal dispersions of poly(sodium acrylate)-protected silver nanoclusters

Silver nanoclusters protected by poly(sodium acrylate) (PAA) were prepared by UV irradiation of an alcohol–water solution of silver perchlorate in the presence of PAA. Colloidal dispersions of PAA-protected Ag nanoclusters (PAA–Ag nanoclusters) were very stable at room temperature for months and composed of fine particles with an average diameter of 4.2 nm. X-Ray photoelectron spectroscopy data have suggested the 0-valency of Ag in PAA–Ag nanoclusters. Oxidation of ethylene, catalyzed by PAA–Ag nanoclusters, was performed in glycol under 1 atm. of ethylene/oxygen (2/1 v/v). Products were identified as ethylene oxide by analysis with gas chromatography. Ag nanoclusters thus prepared had higher catalytic activity than a commercial silver catalyst. The oxidation rate catalyzed by the PAA–Ag nanoclusters remarkably increased with increasing reaction temperature. PAA-protected Ag nanoclusters had much higher activity than poly( N-vinyl-2-pyrrolidone)-protected ones at high temperature. Addition of both cesium and rhenium ions eminently increased the catalytic activity of PAA–Ag nanoclusters.

Effect of polyelectrolyte on the lower critical solution temperature of poly( N-isopropyl acrylamide) in the poly(NIPAAm- co-acrylic acid) hydrogel

Temperature/pH sensitive hydrogels were prepared by copolymerizing N-isopropyl acrylamide (NIPAAm) and acrylic acid (AAc). The influence of polyelectrolyte on the lower critical solution temperature (LCST) of temperature/pH sensitive hydrogels was investigated in the pH range of 2∼12. Swelling ratio of hydrogels as a function of pH at various temperatures was obtained by measuring the weight of the hydrogels in buffer solutions. Swelling ratio of the hydrogels in the presence of poly(allyl amine) (PAA) as a polyelectrolyte was also measured at the same conditions. The LCSTs of the poly( N-isopropyl acrylamide- co-acrylic acid) [P(NIPAAm– co–AAc)] hydrogels increased with pH value and disappeared above the p K a value of poly(acrylic acid) (PAAc) except hydrogel containing 10 mol% of AAc. The LCSTs of the P(NIPAAm- co-AAc) hydrogels in the presence of PAA could be observed even above the p K a value of PAAc. At same pH, the LCSTs of the P(NIPAAm- co-AAc) hydrogels in the presence of PAA were lower than those of the P(NIPAAm- co-AAc) hydrogels due to the polyelectrolyte complex formation between PAAc and PAA. The swelling ratio of P(NIPAAm- co-AAc) gel was the largest at 20 mol% of AAc content and decreased by polyelectrolyte complex formation with PAA. The swelling kinetics of P(NIPAAm- co-AAc) hydrogel was strongly dependent on pH value, temperature and polyelectrolyte solute.

Surface Chemical Studies on the Competitive Adsorption of Poly(acrylic acid) and Poly(vinyl alcohol) onto Alumina

The adsorption of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) onto alumina has been studied as a function of pH, both individually and in the presence of each other. The adsorption density of PAA is found to decrease with an increase of pH while that of PVA shows the opposite trend. In a binary system containing PAA and PVA, the presence of PVA does not affect the adsorption of PAA onto alumina, but the addition of PAA diminishes the adsorption of PVA in the pH range investigated. The adsorption isotherm of PAA at acidic pH exhibits high-affinity Langmuirian behavior. The isotherms for PVA appear rounded and are of the low-affinity type. Once again the adsorption isotherms of PAA remain unaltered in the presence of PVA whereas those of PVA are significantly affected resulting in a lowering of the adsorption density consequent to PAA addition. A variation in the sequence of addition of PAA and PVA does not affect the adsorption behavior of either of the polymers. The electrokinetic behavior of alumina with PAA is hardly influenced by the addition of PVA. On the other hand, the electrophoretic mobility of alumina in the presence of PVA is significantly altered in the presence of PAA and closely resembles the trend observed with PAA alone. Desorption studies reveal that over 80% of PVA could be desorbed in the pH range 3–9 whereas in the case of PAA, the percent desorption increases from 20 to about 70% as the pH is increased from about 3 to 8. Solution conductivity tests confirm interaction of aluminum species and PAA in the bulk solution. FTIR spectroscopic data provide evidence in support of hydrogen bonding and chemical interaction in the case of the PAA–alumina system and hydrogen bonding with respect to the PVA–alumina interaction.

Distribution of a novel locus called Paa (porcine attaching and effacing associated) among enteric Escherichia coli.

Using TnphoA transposon insertion mutagenesis, we found a porcine EPEC (PEPEC) mutant demonstrating as inability to induce AE lesions. The insertion was identified in a gene designated paa (porcine attaching and effacing associated). The distribution of paa in PEPEC O45 strains revealed that it was associated with presence of the eae and its AE phenotype in vivo. On examination of enteric E. coli isolates from humans and various animal species, a strong correlation with the presence of paa was found in EHEC O157:H7 and O26, and dog, rabbit, and pig eae-positive isolates, and to a lesser extent in human EPEC eae-positive isolates. Also, among porcine ETEC isolates, a strong association was found with the presence of LT encoded genes. In contrast, paa sequence was rarely found in enteric E. coli isolates lacking ETEC and AEEC virulence determinants. Thus, our results suggest that Paa could play a role in the AE mechanism and other mechanisms of enteric disease.

Effects of macromolecules on the crystallization of CaCO 3 the Formation of Organic/Inorganic Composites

The effects of macromolecules as soluble additives and solid matrices have been examined for the crystallization of CaCO 3. A vaterite form grows on a glass substrate in the presence of poly(glutamic acid) (PGA) containing a carboxylic acid group as a soluble additive. In contrast, no crystal growth has been observed when poly(acrylic acid) (PAA) exists as an additive though it has the same functional group. The conformation or the backbone structure of the polymers may have an influence on the crystal polymorph of CaCO 3. Thin film states of CaCO 3 crystals have been obtained as organic/inorganic composites with chitosan that acts as a solid matrix in the presence of PAA or PGA as a soluble additive.

Competitive Adsorption of PVA and PAA on Alumina Surface

A variety of organic polymer is used in ceramic processing as binders and dispersants, etc. Their adsorption on the surface of ceramic particles as well as their effect on rheology of ceramic slurry are an important topic in studies on ceramic processing. In systems containing two or more kinds of polymers, the adsorption as well as the function of a specific polymer can be affected by other coexisting polymers. This paper reports the competitive adsorption of PVA and PAA in the alumina system. The original roles of the former and the latter are binder and dispersant, respectively. Various slurries were prepared by changing the adding order of these organic additives. The slurry viscosity was measured with a rotary viscometer. Adsorption of PVA on the alumina surface was found to be hindered markedly by the presence of PAA. However, that of PAA was not affected by the presence of PVA. Clearly, the adsorption of PVA on solid surface is much weaker than that of PAA. (orig.) 14 refs.

Extensions of polyacrylic acid ammonium salts in the adsorption layer to fluidize alumina slurries

An average shell volume occupied in the adsorption layer on alumina by a polyacrylic acid ammonium salts molecule (PAA) defined as the average area occupied by an adsorbed PAA on alumina multiplied by the average thickness of the water layer at the limit of thickening, has been calculated from the adsorbed amount of PAA and from the flow points of alumina in the presence of PAA of different molecular weights. A steric effect of the PAA dispersant on the dispersion of alumina resulted in a flow with no yield stress. This was due to the change of the extension of PAA in the adsorption shell from a sphere to an ellipsoid with a long axis which exceeded the effective distance that the van der Waals attraction force reaches at a molecular weight for the PAA of between 10 000–20 000.

The HSV-1 UL45 18 kDa gene product is a true late protein and a component of the virion

Previously we constructed a null mutation in the HSV-1 UL45 gene, showed that the UL45 gene was not required for growth in Vero cells, and confirmed that it coded for an 18 kDa protein (R.J. Visalli and C.R. Brandt, Virology 185: 419–423, 1991). In this study, we have continued our characterization of the UL45 gene and the 18 kDa protein. Analysis of UL45 RNA revealed that the gene was expressed late and was inhibited in the presence of phosphonoacetic acid (paa), indicating it is a γ 2 class gene. Using a specific polyclonal antiserum, we found that the 18 kDa UL45 gene product was also expressed late and was inhibited in the presence of paa. The 18 kDa protein was present in purified virions and was substantially enriched in the envelope-tegument fraction of virions disrupted with NP-40 detergent. The 18 kDa protein is thus a structural protein of the virus and appears to be associated with the viral envelope. A 20 kDa protein that cross-reacted with a polyclonal HSV-1 UL45 antiserum was also detected in cells infected with HSV-2 strain 333.

Evidence of complexation between poly(acrylic acid) and sodium dodecyl sulfate

Interactions between poly(acrylic acid) (PAA) and sodium dodecyl sulfate (SDS) in aqueous solution were studied using fluorescence spectroscopy. Pyrene labeled PAA was used to study changes in conformation of the polymer on its association with SDS. Externally added pyrene was used to study the aggregation behavior of the surfactant in the absence and presence of PAA. Effects of polymer concentration and pH were determined. It was observed that PAA and SDS interact, under acidic pH conditions, when the PAA concentration is low. Under conditions where the PAA is ionized, there are no interactions between PAA and SDS, but if the polymer concentration is high then an increase in ionic strength due to the dissociation of a large number of carboxylic acid groups results in aggregation of the surfactant, even at concentrations much lower than its critical micelle concentration in the absence or any polymer.

Complex formation between bovine serum albumin and poly(acrylic acid) as studied by viscometry, circular dichroism, and fluorescence spectroscopy

AbstractThe complex formation between bovine serum albumin (BSA) and poly(acrylic acid) (PAA) in water was studied by viscosity measurements. It was found that at a BSA/PAA mole ratio of 233 the reduced viscosity of the solution shows a minimum, indicating that binding take place nonspecifically on the BSA surface. Circular dichroism (CD) spectra indicate that BSA does not suffer conformational alteration by the presence of PAA. Fluorescence spectroscopic studies were performed on 1‐anilinonaphthalene‐8‐sulfonate(ANS)‐BSA systems in presence of monocarboxylic acids or PAA. Again, in contrast to the hydrophobic binding of the monoacids, it was found that PAA binds to BSA nonspecifically on the surface.

Interaction of fractionated poly(acrylic acid)s with bovine serum albumin

The interaction of fractionated poly(acrylic acid)s (PAA) with bovine serum albumin (BSA) has been studied by measuring the hydrolysis rate of p-nitrophenyl acetate catalysed by BSA in the presence of PAA. The binding of PAA with BSA, which prohibits the catalytic action of BSA, increases with increasing molecular weight of PAA. The change in the electronic spectra of BSA-PAA solutions supports this molecular weight dependence. Circular dichroism of BSA shows that the binding of PAA does not induce any conformational change in BSA.

Reversible inhibition by phosphonoacetic acid of human B lymphocyte transformation by Epstein-Barr virus

B lymphocytes purified by immunoabsorbent chromatography from the peripheral blood lymphocytes of adults provide highly effective targets for infection and transformation by Epstein-Barr virus (EBV). Using this system, the kinetics of DNA synthesis induction due to EBV infection have been characterized. The kinetics show two phases: an early phase, lasting 3 to 4 days, the rate and absolute level of which are dependent upon multiplicity of infection; and a later phase, representing normal exponential growth, the level but not rate of which is dependent upon multiplicity of infection. The induction of DNA synthesis begins at a time (24 hr) which agrees well with the published times for the appearance of the Epstein-Barr virus nuclear antigen (EBNA). Absorption and penetration of the cells by EBV appear to require 1 to 2 hr. The induction of DNA synthesis proceeds normally during the first phase in the presence of phosphonoacetic acid (PAA; 200 μg/ml). Thereafter, DNA synthesis remains at a plateau. Blast-transformed EBNA-positive cells may be isolated from these cultures. Removal of PAA at any time up to 28 days postinfection results in resumed proliferation and outgrowth. These cells express four phenotypic properties of transformation by EBV: (1) induction of DNA synthesis, (2) EBNA expression, (3) blast transformation, and (4) immortalization (survival for at least 28 days). However, they cannot grow out. It is therefore proposed that the phenomenon of EBV infection in the presence of PAA may be termed “abortive transformation.”

Hydrolysis of N-Vinyl-2-oxazolidone in the Presence of Polyacids

Hydrolysis of N-vihyl-2-oxazolidone (NVOx) in the presence of polyacids, such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA) and poly(L-glutamic acid) (PLG) was investigated. The break in the presence of PMAA or PLG were observed at pH=5.1, v5.2, where the conformation of PMAA or PLG changes; no the break was observed in the presence of PAA, however.The hydrolysis of NVOx was also examined in the presence of isotactic PMAA(PMAA), syndiotactic PMAA (s-PMAA) and atactic PMAA (a PMAA). lt was found that the rate of hydrelysis increased as follows;i-PMAA s-PMAA s: a-PMAAFurthermore, the salt effect on the hy, drolysis of NVQx ip thg. presenge gf. aceSic acid or PMAA was studied. The rate of hydrblysis increased by the addition of salt in the presence 6f acetic acid, while the rate decreased in the presence of PMAA. t Syntheses and Reaction of Functienal Pelymers. LXXVI.