Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The particle size distribution (PSD) of suspended hydroxyapatite crystallites both at equilibrium and during crystal growth has been measured by a laser scattering technique. Addition of high-molecular-weight polyacrylate (PAA/C) resulted in appreciable crystallite aggregation, probably by polymer bridging of particles. In contrast, a lower-molecular-weight PAA was unable to bridge the hydrodynamic gap between particles and resulted in an overall dispersion. The addition of human serum albumin also markedly influenced the PSD and, with concomitant change in zeta potential to more negative values, resulted in dispersion due to steric interaction and electrostatic repulsion between the particles. The complex behavior of human saliva is illustrated by its tendency both to aggregate and to disperse hydroxyapatite crystallites, displaying the combined effects of different adsorbing macromolecules.
 ...
PMID:Analysis of particle size distribution of hydroxyapatite crystallites in the presence of synthetic and natural polymers. 217 Apr 83

In the present study, we investigated whether auto-anti-idiotypic antibody in the immune sera from old mice could recognize antitrinitrophenyl (TNP) plaque-forming cells (PFC) generated after stimulation with the T-dependent and T-independent forms of the hapten, TNP. Young and old C57BL/6J male mice were immunized with a variety of T-dependent (TNP-bovine gamma-globulin, TNP-BGG; TNP-keyhole Limpet hemocyanin, TNP-KLH; ovalbumin, OVA; bovine serum albumin, BSA; BGG) and T-independent (TNP-Brucella abortus, TNP-BA; TBP-Ficoll; TNP-polyacrylamide beads, TNP-PAA) antigens either in complete Freund's adjuvant (CFA) or in soluble form. Splenic anti-TNP or antiprotein PFC responses were assayed for anti-idiotype-blocked, hapten- or protein-augmentable IgM, IgG and IgA PFC, 1-2 weeks after immunization. It was found that 8-month-old mice produced significantly a higher percentage of hapten augmentable (26-42%) IgM PFC response to T-independent antigens as compared with the 2-month-old mice (3-6% augmentation). Similarly, old mice produced a significantly higher percentage of hapten or protein augmentable (25-129%) IgG PFC response to T-dependent antigens as compared with the 2-month-old group (2-6% augmentation). The data support the view that age-related regulation of auto-anti-idiotypic antibody is a general phenomenon for immune responses to T-dependent and T-independent antigens. Hapten-reversible inhibition of plaque formation was used to determine whether anti-idiotypic antibody containing antisera from old mice could inhibit B-cell idiotype repertoires generated after stimulation with the same hapten, TNP, on T-dependent and T-independent carriers. Pools of immune sera from 8-month-old mice primed with T-dependent TNP-BGG or TNP-KLH antigens but not with T-independent TNP-PAA or TNP-BA antigens, or with the proteins OVA, BSA, or BGG selectively inhibited IgM, IgG, and IgA anti-TNP PFC from 2-month-old mice that were previously primed with either TNP-BGG or TNP-KLH. In contrast, immune sera from old mice primed with TNP on either T-dependent or T-independent carriers inhibited anti-TNP PFC from mice primed with T-independent TNP-PAA or TNP-BA antigens. Immune sera from old mice primed with OVA or BSA only inhibited the respective antiprotein PFC. The immune sera from young mice did not show any appreciable inhibition of PFC generated after stimulation by any of the antigens studied.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Selective suppression by auto-anti-idiotypic antibody of B-cell idiotype repertoires generated after stimulation with the same hapten on T-dependent and T-independent carriers. 636 Mar 82

The uptake characteristics of negatively-charged liposomes made by conjugation of poly(acrylic acid) (PAA) were studied with respect to cultured RAW macrophages. The PAA-conjugated liposomes were internalized and digested in an acidic compartment at a much faster rate than the unmodified phosphatidylcholine (PC) liposomes. After incubation for 18 h, an over 5-fold increase in the uptake of PC liposomes was obtained by PAA conjugation. Subsequently, part of the aqueous phase of the internalized liposomes was exocytosed. Recognition of PAA by the macrophages seems to be responsible for the enhanced uptake of PAA-conjugated liposomes. Cross-competition experiments showed that PAA-conjugated liposomes inhibited the uptake of acetylated-low density lipoprotein (acetyl-LDL) by the macrophages and vice versa. The uptake of PAA-conjugated liposomes was also inhibited by dextran sulfate and maleylated-bovine serum albumin (maleyl-BSA), which are also known to bind to scavenger receptors. Poly(C) and BSA, which are not ligands for the scavenger receptor, competed poorly with the uptake of PAA-conjugated liposomes. Enhanced uptake of PAA-conjugated liposomes by CHO cells with low scavenger receptor expression was not observed. Unexpectedly, LDL, which is not a ligand for scavenger receptor, also partially inhibited the uptake of PAA-conjugated liposomes. The interaction of PAA-conjugated liposomes with macrophages is complex, and the endocytosis of PAA-conjugated liposomes most likely involves multiple receptors and/or pathways. The data obtained suggest that the high affinity binding of PAA-conjugated liposomes to macrophages may be due to recognition of the negative charges of PAA by cell surface receptors, including the scavenger receptor.
 ...
PMID:Receptor-mediated endocytosis of poly(acrylic acid)-conjugated liposomes by macrophages. 861 8

Surface-modified human serum albumin (HSA) nanospheres with a size of around 100 nm in diameter were prepared from poly(amidoamine)-poly(ethylene glycol) copolymer grafted human serum albumin (HSA-PAA-PEG) and poly(thioetheramido acid)-poly(ethylene glycol) copolymer grafted human serum albumin (HSA-PTAAC-PEG). The nanospheres were produced using a pH-coacervation method and cross-linked with glutaraldehyde. The cross-linking efficiency was affected by the type of albumin conjugate used. The zeta potential of the surface-modified nanospheres was significantly lower than that of unmodified particles. The existence of a hydrated steric barrier surrounding the nanospheres was confirmed by electrolyte- and pH-induced flocculation tests. The surface-modified nanospheres showed a reduced plasma protein adsorption on the particle surface compared with unmodified particles.
 ...
PMID:Preparation of surface-modified albumin nanospheres. 910 96

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.
 ...
PMID:Ultrafiltration membrane surfaces with grafted polymer 'tentacles': preparation, characterization and application for covalent protein binding. 972 Aug 86

The present study involved comparison of adhesion of Helicobacter pylori KH202 to immobilized Le(b)-oligosaccharide carried on different carriers, i.e. Leb-oligosaccharide conjugated with polyacrylamide, bovine serum albumin, and dipalmitoylphosphatidylethanolamine (Le(b)-PAA, Le(b)-BSA, and Le(b)-DPPE). All of the Le(b)-oligosaccharide-carrying neoglycoconjugates served as ligands for H. pylori. However, H. pylori required 10-fold and 100-fold quantities of Le(b)-antigen to adhere to Le(b)-PAA and to Le(b)-DPPE in comparison to the quantity of Le(b)-antigen needed to adhere to Le(b)-BSA, respectively. H. pylori adhesion to Le(b)-PAA and Le(b)-DPPE was clearly inhibited by Le(b)-oligosaccharide, but adhesion to Le(b)-BSA was hardly inhibited by the oligosaccharide. Therefore, the carbohydrate carrier affects the affinity of H. pylori KH202 toward Le(b)-antigen, although the bacteria recognize Le(b)-antigen regardless of the carbohydrate carrier.
 ...
PMID:Carbohydrate carriers affect adhesion of H. pylori to immobilized Leb-oligosaccharide. 1206 4

Adsorption chromatography in expanded beds is a widely used technology for direct capture of target proteins from fermentation broths. However, in many cases this method cannot be applied as a result of the strong tendency of cells or cell debris to interact with the adsorbent beads. To prevent contamination of the expanded bed with the biomass, STREAMLINE DEAE, anion exchanger designed for expanded bed adsorption, was modified with a layer of poly(acrylic acid) (PAA). The shielding layer of polyelectrolyte was attached to the surface of the matrix beads via electrostatic interactions. PAA with a high degree of polymerization was chosen to prevent diffusion of large polymer molecules into the pores of adsorbent. Thus, the shielding layer of PAA was adsorbed only at the mouth of the pores of STREAMLINE DEAE beads and only marginally decreased the binding capacity of the ion exchanger for bovine serum albumin, the model protein in this study. PAA-coated STREAMLINE DEAE practically did not interact with yeast cells, which otherwise bound strongly to the native adsorbent at neutral conditions. Cell-resistant PAA-coated anion exchanger was successfully used for isolation of BSA from the model protein mixture containing BSA, lysozyme (positively charged at applied conditions), and yeast cells. The layer of PAA was stable under mild elution conditions, and the modified adsorbent could be used in the repeated purification cycles.
 ...
PMID:Polyelectrolyte-coated ion exchangers for cell-resistant expanded bed adsorption. 1215 16

Coating of substrates with polyelectrolyte multilayers terminated with poly(acrylic acid) (PAA) followed by activation of the free -COOH groups of PAA provides a surface that readily reacts with amine groups to allow covalent immobilization of antibodies. The use of this procedure to prepare arrays of antibodies in porous alumina supports facilitates construction of a flow-through system for analysis of fluorescently labeled antigens. Detection limits in the analysis of Cy5-labeled IgG are 0.02 ng/mL because of the high surface area of the alumina membrane, and the minimal diameter of the substrate pores results in binding limited by kinetics, not mass transport. Moreover, PAA-terminated films resist nonspecific protein adsorption, so blocking of antibody arrays with bovine serum albumin is not necessary. These microarrays are capable of effective analysis in 10% fetal bovine serum.
 ...
PMID:Use of porous membranes modified with polyelectrolyte multilayers as substrates for protein arrays with low nonspecific adsorption. 1638 20

The adsorption of two different proteins at a planar poly(acrylic acid) (PAA) brush was studied as a function of the ionic strength of the protein solutions applying total internal reflection fluorescence (TIRF) spectroscopy. Planar PAA brushes were prepared with a grafting density of 0.11 nm(-2) and were characterized using X-ray reflectometry. Hen egg-white lysozyme and bovine serum albumin (BSA) were used as model proteins, which have a net positive and negative charge at neutral pH-values, respectively. It has been found that both proteins adsorb strongly at a planar PAA brush at low ionic strength. Whereas lysozyme interacts with a PAA brush under electrostatic attraction at neutral pH-values, BSA binds under electrostatic repulsion at pH > 5. Even at pH = 8, significant amounts of BSA are adsorbed to a planar PAA brush. In addition, the reversibility of BSA adsorption has been characterized. Dilution of a BSA solution leads to an almost complete desorption of BSA from a PAA brush at short contact times. When the ionic strength of the protein solutions is increased to about 100-200 mM, a planar PAA brush appears largely protein-resistant, regardless of the protein net charge. The results of this study indicate that the salt-dependent protein affinity of a PAA brush represents a unique effect that must be explained by a novel protein-binding mechanism. On the basis of a recent model, it is suggested that a release of counterions is the most probable driving force for protein adsorption at a PAA brush. In a general view, this study characterizes a planar PAA brush as a new materials coating for the controlled immobilization of proteins whose use in biotechnological applications appears to be rewarding.
 ...
PMID:Characterization of a planar poly(acrylic acid) brush as a materials coating for controlled protein immobilization. 1654 92

Polymeric coatings with high protein-binding capacities are important for increasing the output of affinity-based protein purification and decreasing the detection limits of antibody microarrays. This report describes the use of thick poly(acrylic acid) (PAA) brushes to immobilize as much as 80 monolayers of protein. The brushes were prepared using a recently developed procedure that allows polymerization of 100-nm-thick poly(tert-butyl acrylate) films from a surface in just 5 min along with hydrolysis of these films to PAA in 15 min. Covalent binding of bovine serum albumin (BSA) to PAA brushes that were activated using standard coupling agents, however, resulted in immobilization of less than two monolayers of BSA because of competitive hydrolysis of the esters in the activated film. In contrast, derivatization of PAA with nitrilotriacetate (NTA)-Cu2+ complexes yielded films capable of binding many monolayers of protein via metal-ion affinity interactions. For example, derivatization of 55-nm-thick PAA films with NTA-Cu2+ allowed immobilization of about 15 monolayers (5.8 microg/cm2 or 58 nm) of BSA. The binding capacity was even higher for myoglobin (7.7 microg/cm2) and anti-IgG (9.6 microg/cm2). Remarkably, electrostatic adsorption of lysozyme in 55-nm-thick, underivatized PAA resulted in as much as 80 monolayers (16.2 microg/cm2 or 162 nm) of adsorbed protein. Polymer synthesis, derivatization, and swelling, as well as BSA immobilization kinetics and thermodynamics were characterized using reflectance FT-IR spectroscopy, ellipsometry, and protein assays.
 ...
PMID:High-capacity binding of proteins by poly(acrylic acid) brushes and their derivatives. 1661 75


1 2 3 4 5 6 7 Next >>