Ethylene entrapped

The last example deals with submerged Rumex species. A hypoxic atmosphere thus exists in the tissue because gas diffusion is limited in water. In contrast to Rumex acetosuy Rumex palustris shows stimulated shoot elongation in response to submergence paralleled and triggered by drastic enhancement of ethylene concentration. This elongation response is functionally related to the opportunity to reach better illuminated and aerated zones close to the water surface or preferentially above it (Voesenek and van der Veen 1994). Desubmergence of the species displays a first peak in ethylene emission with a subsequent second rise followed by a slow decay (Fig. 10). As discussed by Voesenek et al. (1993), the first peak is due to release of entrapped ethylene. The second rise corresponds to a temporary... 

For the preparation of nanoparticles based on two aqueous phases at room temperature one phase contains chitosan and poly(ethylene oxide) and the other contains sodium tripolyphosphate. The particle size (200-1000 nm) and zeta potential (between -i- 20 mV and -l- 60 mV) could be modulated by varying the ratio chitosan/PEO-PPO. These nanoparticles have great proteinloading capacity and provide continuous release of the entrapped protein (particularly insulin) for up to one week [100,101]. 

Dendrimer micelles of this type have been formulated as drug delivery vehicles. Dendrimers with a hydrophobic interior have been used to entrap a hydrophobic drug such as indomethacin. This is retained because of the hydrophilic periphery containing ethylene glycol functional groups, and is released slowly because of the collapsed configuration of the interior, through which molecular diffusion is obstructed. 

Dynamic light-scattering experiments or the analysis of some physicochemical properties have shown that finite amounts of formamide, A-methylformamide, AA-dimethyl-formamide, ethylene glycol, glycerol, acetonitrile, methanol, and 1,2 propanediol can be entrapped within the micellar core of AOT-reversed micelles [33-36], The encapsulation of formamide and A-methylformamide nanoclusters in AOT-reversed micelles involves a significant breakage of the H-bond network characterizing their structure in the pure state. Moreover, from solvation dynamics measurements it was deduced that the intramicellar formamide is nearly completely immobilized [34,35],... 

In spite of the potentialities of reversed micelles entrapping nonaqueous highly polar solvents [34], very few investigations on the solubilization in such systems are reported in the literature. An example is the study of the solubilization of zinc-tetraphenylporphyrin (ZnTPP) in ethylene glycol/AOT/hydrocarbon systems by steady-state and transient... 

Solubilization of a graft copolymer comprising a hydrophobic poly(dodecyl-methacrylate) backbone and hydrophilic poly(ethylene glycol) monomethyl ether side chains in water/AOT/cyclohexane w/o microemulsions was rationalized in terms of the backbone dissolved in the continuous apolar phase and the side chains entrapped within the aqueous micellar cores [189],... 

Figure 3. Time dependence of the fraction R of unreacted aminostyrene residues during acetylation by 0.14 M acetic anhydride at 30°C. Methyl methacrylate copolymer in acetonitrile solution (0) linear poly-(methyl methacrylate-co-butyl methacrylate) swollen with acetonitrile Cd) methyl methacrylate copolymer crosslinked with 1 mole% ( ) and with 15 mole% ( ) ethylene dimethacrylate poly(methacrylate crosslinked with 3 mole% ethylene dimethacrylate containing entrapped poly(methyl acrylate-co-aminostyrene) ( ).

The main advantage is that the entrapment conditions are dictated by the entrapped enzymes, but not the process. This includes such important denaturing factors as the solution pH, the temperature and the organic solvent released in the course of precursor hydrolysis. The immobilization by THEOS is performed at a pH and temperature that are optimal for encapsulated biomaterial [55,56]. The jellification processes are accomplished by the separation of ethylene glycol that possesses improved biocompatibility in comparison with alcohols. 

Li X, Deng X, Yuan M et al (2000) In vitro degradation and release profiles of poly-DL-lactide-poly(ethylene glycol) microspheres with entrapped proteins. J Appl Polym Sci 78 140-148... 

Hydrogels are 3D cross-linked polymer networks. They can withstand acid conditions and release the entrapped drug molecules. Purdue University researchers have used a poly[methacrylic acid-g-poly(ethylene glycol)] hydrogel to encapsulate insulin, which could be released by pH trigger. 

Vesicle-entrapped or isolated Pt were used as 564 catalysts for ethylene and cyclohexane hydrogenation... 

If polyurethanes are used to entrap cells, the diffusion wiU depend on the polyol used to build the polyurethane since the polyol defines equilibrium moisture. Later in this chapter, we will discuss a number of entrapment systems, including acrylates and polysaccharides. Each has its own equilibrium moisture and therefore unique diffusion constant. Only polyurethanes, however, offer the opportunity to affect changes in the constants. Conventional hydrophilic polyurethanes have equilibrium moisture levels around 70%. It is possible, however, to increase the molecular weight of a polyol (an ethylene glycol of 1000 molecular weight) to 3000 or more. This increases the equilibrium moisture to greater than 90%. 

Hatada, A. and K. Kataoka. 1998. Novel polyion complex micelles entrapping enzyme molecules in the core preparation of narrowly-distributed micelles from lysozyme and poly(ethylene glycol)-poly(aspartic acid) block copolymer in aqueous mediuWiacromoleculeSI 288-294. 

Yokoyama, M., T. Okano, Y. Sakurai, and K. Kataoka. 1994. Improved synthesis of adriamycin-conjugated poly(ethylene oxide)-poly(aspartic acid) block copolymer and formation of unimodal micellar structure with controlled amount of physically entrapped adriamydirControl. Rel.32 269-277. 

L. Doretti, D. Ferrara, S. Lora, F. Schiavon and F.M. Veronese, Acetylcholine biosensor involving entrapment of acetylcholinesterase and poly (ethylene glycol)-modified choline oxidase in a poly(vinyl alcohol) cryogel membrane, Enzyme Microb. Technol., 27 (2000) 279-285. 

Harada, A., Togawa, H. and Kataoka, K. (2001) Physicochemical properties and nuclease resistance of antisense-oligodeoxynucleotides entrapped in the core of polyion complex micelles composed of poly(ethylene glycol)-poly (L-Lysine) block copolymers. Eur. J. Pharm. Sci., 13, 35—42. 

Fig. 6.33. Scanning electron micrograph of a capillary column packed with 5 pm ODS silica beads and entrapped in porous poly(methyl methacrylate-co-ethylene dimethacrylate-co-2-acrylamido-2-methyl-l-propanesulfonic acid). (Reprinted with permission from [63]. Copyright 2000 American Chemical Society).

PEG-ylated immunoliposomes for CNS drug delivery. The drug is entrapped within a hposome vector to which is attached antibodies on poly(ethylene glycol) linkers... 

Some other recent examples are the use of palladium nanoparticles entrapped in aluminum hydroxide [181], resin-dispersed Pd nanoparticles [182], and poly (ethylene glycol)-stabilized palladium nanoparticles in scC02 [183]. Although in some cases the activities for activated alcohols obtained with these Pd-nanoparti-cles are impressive, the conversion of aliphatic alcohols is still rather slow. 

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