Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Layer-by-layer (LBL) polyelectrolyte films were constructed from poly(L-glutamic acid) (PGA) and poly(L-aspartic acid) (PAA) as polyanions, and from poly(L-lysine) (PLL) as the polycation. The terminating layer of the films was always PLL. According to attenuated total reflection Fourier transform infrared measurements, the PGA/PLL and PAA/PLL films, despite their chemical similarity, had largely different secondary structures. Extended beta-sheets dominated the PGA/PLL films, while alpha-helices and intramolecular beta-sheets dominated the PAA/PLL films. The secondary structure of the polyelectrolyte film affected the adsorption of human serum albumin (HSA) as well. HSA preserved its native secondary structure on the PGA/PLL film, but it became largely deformed on PAA/PLL films. Both PGA and PAA were able to extrude to a certain extent the other polyanion from the films, but the structural consequences were different. Adding PAA to a (PGA/PLL)5-PGA film resulted in a simple exchange and incorporation: PGA/PLL and PAA/PLL complexes coexisted with their unaltered secondary structures in the mixed film. The incorporation of PGA into a (PAA/PLL)5-PAA film was up to 50% and caused additional beta-structure increase in the secondary structure of the film. The proportions of the two polyanions were roughly the same on the surfaces and in the interiors of the films, indicating practically free diffusion for both polyanions. The abundance of PAA/PLL and PGA/PLL domains on the film surfaces was monitored by the analysis of the amide I region of the infrared spectrum of a reporter molecule, HSA, adsorbed onto the three-component polyelectrolyte films.
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PMID:Partial poly(glutamic acid) <--> poly(aspartic acid) exchange in layer-by-layer polyelectrolyte films. Structural alterations in the three-component architectures. 1676 5

The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.
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PMID:Immobilization of enamel matrix derivate protein onto polypeptide multilayers. Comparative in situ measurements using ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry. 1715 85

Alternated deposition of polyanions and polycations on a charged solid substrate leads to the buildup of polyelectrolyte multilayer (PEM) films. Two types of PEM films were reported in the literature: films whose thickness increases linearly and films whose thickness increases exponentially with the number of deposition steps. However, it was recently found that, for exponentially growing films, the exponential increase of the film thickness takes place only during the initially deposited pairs of layers and is then followed by a linear increase. In this study, we investigate the growth process of hyaluronic acid/poly(L-lysine) (HA/PLL) and poly(L-glutamic acid)/poly(allylamine) (PGA/PAH) films, two films whose growth is initially exponential, when the growth process enters the linear regime. We focus, in particular, on the influence of the molecular weight (Mw) of the polyelectrolytes. For both systems, we find that the film thickness increment per polyanion/polycation deposition step in the linear growth regime is fairly independent of the molecular weights of the polyelectrolytes. We also find that when the (HA/PLL)n films are constructed with low molecular weight PLL, these chains can diffuse into the entire film during each buildup cycle, even for very thick films, whereas the PLL diffusion of high molecular weight chains is restricted to the upper part of the film. Our results lead to refinement of the buildup mechanism model, introduced previously for the exponentially growing films, which is based on the existence of three zones over the entire film thickness. The mechanism no longer needs all the "in" and "out" diffusing polyanions or polycations to be involved in the buildup process to explain the linear growth regime but merely relies on the interaction between the polyelectrolytes with an upper zone of the film. This zone is constituted of polyanion/polycation complexes which are "loosely bound" and rich in the polyelectrolyte deposited during the former deposition step.
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PMID:Influence of the polyelectrolyte molecular weight on exponentially growing multilayer films in the linear regime. 1727 72

The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on beta-FeOOH colloidal particles was investigated by means of electro-optics and electrophoresis. The films were built at different (acidic) pH in the absence of salt. We found that the thickness of the film grows linearly when the fully charged PLL (at pH 5.5) is combined with almost fully charged PGA (at pH 6.5), with a thickness of about 2 nm per single layer. When the fully charged PLL is combined with weakly charged PGA (at pH 4.5), the film thickness increases exponentially with the number of deposited layers. The thickness of the exponentially growing film increases to 300 nm after deposition of 16 layers. The exponential film growth is attributed to the ability of the PLL to diffuse "in" and "out" of the film bulk at each deposition step. The variation in the electrical polarizability of the film-coated particles was also monitored as a function of the number of adsorbed layers. The result reveals that the PLL chains, which can diffuse into the film bulk, have no measurable contribution to the electro-optical effect of the films terminated with PLL. It is only due to the polarization of counterions of the PLL adsorbed on the film surface.
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PMID:Polypeptide multilayer films on colloidal particles: an in situ electro-optical study. 1728 83

Dipalmitoylphosphatidylcholine (DPPC) bilayer was created on the surface of an exponentially growing poly(glutamic acid)/poly(lysine) (PGA/PLL) layer-by-layer polyelectrolyte film. The lipid bilayer decreased the surface roughness of the polyelectrolyte film. The layer-by-layer construction of the polyelectrolyte film could be continued on the top of the DPPC layer. The lipid bilayer, however, formed a barrier in the interior of the polyelectrolyte film, which blocked the diffusion (a prerequisite for exponential growth) of the polyelectrolytes. Thus, a new growth regime started in the upper part of the polyelectrolyte film, which was added to embed the DPPC bilayer. The structure and the dynamics of the DPPC bilayer on the polyelectrolyte film surface remained similar to that of its hydrated multibilayers, except that the phase transition became wider. In the case of embedded DPPC bilayers, in addition, the phase-transition temperature also decreased. This is the result of interactions with the nonconcerted movements of the barrier-separated lower and higher parts of the polyelectrolyte film. Gramicidin A (GRA) as a model of lipid-soluble peptides and proteins was successfully incorporated into such DPPC films. The DPPC films, either with or without GRA, were remarkably stable; as many heating-cooling cycles to measure phase transition could be carried out without visible alterations as wanted.
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PMID:Phospholipid bilayers as biomembrane-like barriers in layer-by-layer polyelectrolyte films. 1758 91

Layer-by-layer (LBL) polyelectrolyte films offer extensive potentials to enhance surface properties of vascular biomaterials. From the time of implantation, PET prostheses are continuously subjected to multiple mechanical stresses such as important distorsions and blood pressure. In this study, three LBL films, namely (1) poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride), (2) poly(L-lysine)/hyaluronan, and (3) poly(L-lysine)/poly(L-glutamic acid) were built on to isolated PET filaments, thread, and vascular prostheses. The three LBL films uniformly covered the surface of the PET samples with rough, totally smooth, and "wrinkled" appearances respectively for (PAH/PSS)(24), (PLL/HA)(24), and (PLL/PGA)(24) systems. We then assessed the behavior of these LBL films, in an aqueous environment [by environmental scanning electronic microscopy (ESEM)], when subjected to unidirectional longitudinal stretches. We found that stretching induces ruptures in the multilayer films on isolated filaments for longitudinal stretches of 14% for (PSS/PAH)(24), 13% for (PLL/PGA)(24), and 30% for (PLL/HA)(24) films. On threads, the rupture limit is enhanced to be respectively 26, 20, and 28%. Most interestingly, we found that on vascular prosthesis no rupture is visible in any of the three multilayers types, even for elongations of 200% (200% undergone by the PET prostheses is representative of those encountered during graft deployment) which by far exceeds elongations observed under physiological conditions (10-20%, blood pressure). In term of mechanical behaviors, these preliminary data constitute a first step toward the possible use of LBL film to coat and functionalize vascular prosthesis.
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PMID:Characterization of polyelectrolyte multilayer films on polyethylene terephtalate vascular prostheses under mechanical stretching. 1761 82

Polyelectrolyte multilayers of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) were built up using the layer-by-layer (LbL) technique in low pH (3.6, PM3.6) and in neutral pH (7.4, PM7.4) solutions. The multilayers were then treated with a concentrated urea (one kind of denaturant for proteins and polypeptides) solution (8M) and rinsed with corresponding buffer. The buildup and treatment processes were investigated by ultraviolet visible spectroscopy and ellipsometry. The surface morphology was observed by scanning force microscopy (SFM). The inner structures were determined by X-ray reflectometry and circular dichroism spectroscopy (CD). An exponential growth of the optical mass and the layer thickness was observed for both PM3.6 and PM7.4. After urea treatment, a significant mass loss for PM3.6 was found, while no mass change was recorded for PM7.4. The dominant driving force for PM7.4 is electrostatic interaction, resulting in multilayers with an abundant beta-sheet structure, which has higher stability against urea treatment. By contrast, the dominant driving force for PM3.6 is hydrogen bonding and hydrophobic interaction, which are sensitive to the urea treatment. The mechanism is substantiated by molecular mechanics calculation. This has offered a convenient pathway to mediate the multilayer properties, which is of great importance for potential applications.
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PMID:Influence of assembling pH on the stability of poly(L-glutamic acid) and poly(L-lysine) multilayers against urea treatment. 1806 58

Prospective biomedical applications of hollow polyelectrolyte microcapsules, for example, as drug delivery systems, require surface modifications that help to escape clearance by the mononuclear phagocytic system (MPS). Layer-by-layer assembled microcapsules that were alternatingly composed of polystyrene sulfonate (PSS) and polyallylamine hydrochloride (PAH) were coated with adlayers of poly(ethylene glycol) (PEG)-grafted poly-L-lysine (PLL-g-PEG) and poly-L-glutamic acid (PGA-g-PEG). Their effects on MPS recognition were studied in primary cell cultures of human monocyte derived dendritic cells and macrophages. PGA-g-PEG coatings had no significant effect on cellular recognition, which may be explained by insufficient PEG density of the adlayer. Contrary, PLL-g-PEG effectively blocked phagocytosis of coated microcapsules. In addition, PLL-g-PEG coatings showed efficient adlayer stability for at least 3 weeks, and PAH/PSS microcapsules did not impair phagocyte viability. Our results demonstrate that layer-by-layer assembled polyelectrolyte microcapsules coated with a PEG-grafted polyelectrolyte, PLL-g-PEG, represent a promising platform for a drug delivery system that escapes fast clearance by the MPS.
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PMID:Stable stealth function for hollow polyelectrolyte microcapsules through a poly(ethylene glycol) grafted polyelectrolyte adlayer. 1807 22

Multilayer nanofilms, formed by the layer-by-layer (LbL) adsorption of positively and negatively charged polyelectrolytes, are promising substrates for tissue engineering. We investigate here the attachment and function of hepatic cells on multilayer films in terms of film composition, terminal layer, rigidity, charge, and presence of biofunctional species. Human hepatocellular carcinoma (HepG2) cells, adult rat hepatocytes (ARH), and human fetal hepatoblasts (HFHb) are studied on films composed of the polysaccharides chitosan (CHI) and alginate (ALG), the polypeptides poly(l-lysine) (PLL) and poly(l-glutamic acid) (PGA), and the synthetic polymers poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS). The influence of chemical cross-linking following LbL assembly is also investigated. We find HepG2 to reach confluence after 7 days of culture on only 2 of 18 candidate multilayer systems: (PAH-PSS)(n) (i.e. nPAH-PSS bilayers) and cross-linked (PLL-ALG)(n)-PLL. Cross-linked PLL-ALG and PLL-PGA films support attachment and function of ARH, independently of the terminal layer, provided collagen is adsorbed to the top of the film. (PAH-PSS)(n), cross-linked (PLL-ALG)(n), and cross-linked (PLL-PGA)(n)-PLL films all support attachment, layer confluence, and function of HFHb, with the latter film promoting the greatest level of function at 8 days. Overall, film composition, terminal layer, and rigidity are key variables in promoting attachment and function of hepatic cells, while film charge and biofunctionality are somewhat less important. These studies reveal optimal candidate multilayer biomaterials for human liver tissue engineering applications.
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PMID:Multilayer nanofilms as substrates for hepatocellular applications. 1865 30

The buildup mechanism of polypeptide multilayers prepared by the layer-by-layer deposition of a polyanion (poly(L-glutamic acid) (PGA)) and polycations (poly(L-lysine) (PLL), poly(D-lysine) (PDL), and copoly(DL-lysine)(PDLL)) was reinvestigated by using in situ ATR-IR spectroscopy. A difference spectral technique applied to analyze the spectra indicated that the deposition of both the PGA and PLL (PDL) layers accompanies the formation of secondary structures consisting mainly of the antiparallel pleated sheet (the beta-sheet) structure, and that the formation of the beta-sheet structure cannot always be explained in terms of polyanion/polycation complex formation or charge compensation between the polyanion and polycations, although it has been considered as a major process in the multilayer buildup process. Instead, the present paper proposes the following mechanism. During the deposition of the polyelectrolyte, a small amount of the beta-sheet structures are produced at the interface as a result of charge compensation between a polyelectrolyte and an oppositely charged polyelectrolyte in the multilayer. The beta-sheets act as nuclei from which further propagation of the structure takes place at the solution/multilayer interfaces. The driving force of the buildup process in the new mechanism is a kinetically favorable insolubilization of each polyelectrolyte in solution at the interfaces.
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PMID:Reinvestigation on the buildup mechanism of alternate multilayers consisting of poly(L-glutamic acid) and poly(L-, D-, and DL-lysines). 1897 12


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