Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel polypeptide hydrogel has been synthesized by crosslinking poly(L-glutamic acid) (PLG) with poly(ethylene glycol) (PEG). The PLG-PEG hydrogel was shown to be highly hydrophilic, and the extent of swelling varied with pH, increasing at higher ionization of the PLG. Aside from electrostatic effects, such as ion-ion repulsion and internal ion osmotic pressure, circular dichroism studies showed that swelling response to pH also is affected by secondary structural attributes associated with the polypeptide backbone. Modification of the polypeptide by changing its hydrophobicity and degree of ionization was an effective method for altering the overall extent of pH-responsive swelling. Rapid de-swelling (contraction) was observed when the PLG-PEG hydrogel was transferred from high to low pH buffer solution, and this swelling/de-swelling behavior was reversible over repeated cycles. Drug release from swollen hydrogels was examined using the model protein lysozyme. Rapid de-swelling of the hydrogel was found to be an effective means of facilitating lysozyme release. The crosslinking of synthetic polypeptides with PEG appears to be a highly versatile approach to the preparation of pH-responsive biodegradable hydrogels.
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PMID:A pH- and ionic strength-responsive polypeptide hydrogel: synthesis, characterization, and preliminary protein release studies. 1049 96

Protein inactivation and aggregation at the water/CH2Cl2 interface is one of the most detrimental events hindering the encapsulation of structurally unperturbed proteins into poly(lactide-co-glycolide) (PLG) microspheres for their clinical application as sustained release dosage forms. We have investigated the inactivation and aggregation of the model protein hen egg-white lysozyme at this interface and devised methods to prevent both events. When lysozyme was exposed to a large water/CH2Cl2 interface achieved by homogenization, lysozyme aggregation occurred. Fourier-transform infrared (FTIR) spectroscopic data demonstrated that the aggregates formed contained intermolecular beta-sheets. The aggregates were of a noncovalent nature because they slowly dissolved in D2O and the IR spectral bands typical for the intermolecular beta-sheets disappeared at approximately 1617 and 1690 cm(-1). The observed loss in specific enzyme activity of soluble lysozyme was caused by the irreversible formation of an unfolded lysozyme species, which was found to be monomeric, and was able to leave the water/CH2Cl2 interface and accumulate in the aqueous phase. Polyols were, in a concentration dependent fashion, efficient in ameliorating lysozyme unfolding and aggregation. However, prevention of lysozyme aggregation and activity loss in the various samples were unrelated. Thus, polyols must work by more than one mechanism preventing the two events. For the first time, an excipient effect on the conformational stability of lysozyme has been excluded from contributing to the prevention of lysozyme unfolding and aggregation.
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PMID:Improved activity and stability of lysozyme at the water/CH2Cl2 interface: enzyme unfolding and aggregation and its prevention by polyols. 1157 4

This work examines physico-chemical properties influencing protein adsorption to anionic PLG microparticles and demonstrates the ability to bind and release vaccine antigens over a range of loads, pH values, and ionic strengths. Poly(lactide-co-glycolide) microparticles were synthesized by a w/o/w emulsification method in the presence of the anionic surfactant DSS (dioctyl sodium sulfosuccinate). Ovalbumin (OVA), carbonic anhydrase (CAN), lysozyme (LYZ), lactic acid dehydrogenase, bovine serum albumin (BSA), an HIV envelope glyocoprotein, and a Neisseria meningitidis B protein were adsorbed to the PLG microparticles, with binding efficiency, initial release and zeta potentials measured. Protein (antigen) binding to PLG microparticles was influenced by both electrostatic interaction and other mechanisms such as van der Waals forces. The protein binding capacity was directly proportional to the available surface area and may have a practical upper limit imposed by the formation of a complete protein monolayer as suggested by AFM images. The protein affinity for the PLG surface depended strongly on the isoelectric point (pI) and electrostatic forces, but also showed contributions from nonCoulombic interactions. Protein antigens were adsorbed on anionic PLG microparticles with varying degrees of efficiency under different conditions such as pH and ionic strength. Observable changes in zeta potentials and morphology suggest the formation of a surface monolayer. Antigen binding and release occur through a combination of electrostatic and van der Waals interactions occurring at the polymer-solution interface.
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PMID:An investigation of the factors controlling the adsorption of protein antigens to anionic PLG microparticles. 1620 Jun 15

Using YPLG (Tyr-Pro-Leu-Gly), a tetrapeptide, as the template, an imprinted monolithic column was prepared and applied to the selective recognition of oxytocin based on the epitope approach and capillary electrochromatography (CEC). By optimizing the polymerization solution in terms of functional monomer, cross-linking reagent, porogen, and imprinted template via CEC evaluations of synthesized columns, an imprinted monolith with good recognition capacity (the imprinting factors for YPLG and oxytocin were 4.499 and 4.013, respectively) and high column efficiency (theoretical plates for YPLG and oxytocin were 22,995 plates/m and 16,952 plates/m, respectively) was achieved. In addition, the effects of various experimental parameters on the recognition of oxytocin, including the organic modifier content, the buffer concentration, and the pH value, were studied systematically. Furthermore, a mixture of oxytocin and other proteins was analyzed using this monolithic CEC column, and oxytocin was eluted much more slowly than other large biomolecules, which demonstrated the high selective recognition ability of such an imprinted monolith for oxytocin with PLG (Pro-Leu-Gly) as the epitope. Figure Separation of a mixture of oxytocin, BSA, bovine hemoglobin, ovalbumin, and lysozyme on the open column, the blank monolithic column, and the monolithic YPLG-imprinted column.
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PMID:Recognition of oxytocin by capillary electrochromatography with monolithic tetrapeptide-imprinted polymer used as the stationary phase. 1755 31

The chemical composition of the surface of anionic PLG microparticles before and after adsorption of vaccine antigens was measured using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The interfacial distributions of components will reflect underlying interactions that govern properties such as adsorption, release, and stability of proteins in microparticle vaccine delivery systems. Poly(lactide-co-glycolide) microparticles were prepared by a w/o/w emulsification method in the presence of the anionic surfactant dioctyl sodium sulfosuccinate (DSS). Ovalbumin, lysozyme, a recombinant HIV envelope glyocoprotein and a Neisseria meningitidis B protein were adsorbed to the PLG microparticles, with XPS and time-of-flight secondary mass used to analyze elemental and molecular distributions of components of the surface of lyophilized products. Protein (antigen) binding to PLG microparticles was measured directly by distinct elemental and molecular spectroscopic signatures consistent with amino acids and excipient species. The surface sensitive composition of proteins also included counter ions that support the importance of electrostatic interactions being crucial in the mechanism of adsorptions. The protein binding capacity was consistent with the available surface area and the interpretation of previous electron and atomic force microscope images strengthened by the quantification possible by XPS and the qualitative identification possible with TOF-SIMS. Protein antigens were detected and quantified on the surface of anionic PLG microparticles with varying degrees of efficiency under different adsorption conditions such as surfactant level, pH, and ionic strength. Observable changes in elemental and molecular composition suggest an efficient electrostatic interaction creating a composite surface layer that mediates antigen binding and release.
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PMID:Characterization of antigens adsorbed to anionic PLG microparticles by XPS and TOF-SIMS. 1772 59

The use of microspheres and nanospheres of poly(d,l-lactide-co-glycolide) (PLG) as a controlled-release drug delivery system has been the subject of great interest for at least two decades within the field of pharmaceuticals. Salts of zinc and other divalent cations are sometimes co-encapsulated in PLG particles to control the pH or to stabilize encapsulated proteins or peptides. Zinc salts are known to affect pore formation and other processes that may lead to the release of an encapsulated drug. In this study the effect of encapsulated zinc acetate on protein diffusion through PLG films was investigated. PLG films, with and without encapsulated zinc acetate, were degraded in Hepes buffer for different periods of time. The films were subsequently subjected to various kinds of analyses: diffusion properties (using a diffusion cell), porosity (using scanning electron microscopy) and thickness (using light microscopy and an image-analysis program). Encapsulated zinc acetate had a considerable effect and increased the diffusion coefficient of lysozyme through PLG films degraded for 18 days or longer. Films containing zinc acetate became porous, while those without zinc acetate only developed cavities on the surface. Zinc salts may thus be used as release-modifying agents. This effect should be considered when using zinc salts as protein stabilizers or pH neutralizers.
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PMID:Encapsulated zinc salt increases the diffusion of protein through PLG films. 1907 44

Covalent grafting of poly(ethylene glycol) chains to proteins ("PEGylation") is emerging as an effective technique to increase the in vivo circulation time and efficacy of protein drugs. PEGylated protein adsorption at a variety of solid/aqueous interfaces is a critical aspect of their manufacture, storage, and delivery. A special category of block copolymer, PEGylated proteins have one or more water-soluble linear polymer (PEG) blocks and a single globular protein block that each exert distinct intermolecular and surface interaction forces. We report the impact of PEGylation on protein adsorption at the interface between aqueous solutions and solid films of poly(lactide-co-glycolide) (PLG), a moderately hydrophobic and negatively charged polymer. Using the model protein lysozyme with controlled degrees of PEGylation, we employ total internal reflection fluorescence techniques to measure adsorption isotherms, adsorption reversibility, and the extent of surface-induced aggregation. Lysozyme PEGylation reduces the extent of protein adsorption and surface-induced aggregation and increases the reversibility of adsorption compared to the unconjugated protein. Results are interpreted in terms of steric forces among grafted PEG chains and their effects on protein-protein interactions and protein orientation on the surface.
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PMID:Protein PEGylation attenuates adsorption and aggregation on a negatively charged and moderately hydrophobic polymer surface. 2106 42