Amphiphilic polymer polyethylene glycol

Adsorption on solid matrices, which improves (at optimal protein/support ratios) enzyme dispersion, reduces diffusion limitations and favors substrate access to individual enzyme molecules. Immobilized lipases with excellent activity and stability were obtained by entrapping the enzymes in hydrophobic sol-gel materials [20]. Finally, in order to minimize substrate diffusion limitations and maximize enzyme dispersion, various approaches have been attempted to solubilize the biocatalysts in organic solvents. The most widespread method is the one based on the covalent linking of the amphiphilic polymer polyethylene glycol (PEG) to enzyme molecules [21]. 

Sirolimus is insoluble in water, having poor systemic bioavailability estimated at 18% following ingestion of the tablet. The polymers, polyethylene glycol 8000, polyethylene glycol 20000, and poloxamer 188 (a nonionic amphiphilic copolymer surfactant) augment water solubility and miscibility of SRL tablets [1]. Though SRL tablets are taken just once daily, this does not constitute an extended- or delayed-release formulation per se, as the half-life of SRL is approximately 60 hours. 

Generally, the amphiphilic core/shell stmcture of polymeric micelles is formed from block polymers. Polyethylene glycol (PEG) and polyethylene oxide (PEO) are often used as the hydrophilic blocks. They have been shotvn to prevent recognition by the reticuloendothelial system and increase circulation time in vivo. As in the case of liposomes and niosomes, the grafting of specific ligand molecules on the surface of the polymeric micelles allows... 

Chemical modification such as adding polyethylene glycol polymers can improve the in vivo characteristics of peptides. An example is CT-025, which is a diconjugate of recombinant salmon calcitonin (sCT).62 The chemical modification of sCT results in an orally available diconjugate that retains hormonal activity while having increased amphiphilicity. Modification can occur at sites where an amine is available. On sCT, there are sites at Cys-1, Lys-11, and Lys 18, as shown in Figure 10.1. 

Pd is an expensive metal. In Pd(0) or Pd(II)-catalyzed reactions, particularly in commercial processes, repeated uses of Pd catalysts are required. When products are low-boiling, they can be separated from the catalyst by distillation. The Wacker process for the production of acetaldehyde is an example, hi order to separate from less volatile products, there are several approaches for the economical use of Pd catalysts. Active Pd complexes covalently bound to a polymer chain are frequently used. After the reaction, the supported catalyst can be recovered by filtration and reused several times. Polymers such as the Merrifield resin [25], amphiphilic poly(ethylene glycol)-polystyrene copolymer [26] and polyethylene [27] are typical examples. Also polymer-supported microencapsulated Pd is used as a reusable... 

Uozumi and coworkers prepared phosphine/palladium complexes supported on polyethylene glycol-polystyrene graft polymer. - This amphiphilic resin-supported palladium complex eftidently catalyzed the alkylation of allylic acetates in water with various nucleophiles including 1,3-dicarbonyl compounds, amino acids, sodium azide, sodium sulfinate, phenylboronic acid, and sodium tetraphenylborate to give the corresponding allylic-substituted products in quantitative yields. 

Wang, Y. H. and Y. L. Hsieh (2004). Enzyme immobilization to ultra-fine cellulose fibers via amphiphilic polyethylene glycol spacers. Journal of Polymer Science Part A Polymer Chemistry 42(17) 4289-4299. 

Additional agents aimed at adjusting the physical-chemical characteristics of the solution can also be used. For instance, surfactants or amphiphilic copolymers can be added to facilitate the homogeneous wetting of low energetic substrates, whereas the viscosity of the solution can be increased with the addition of the polyethylene glycol or other polymers with different degrees of polymerization. 

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