Labile junctions

Figure 10.34, curve 1 shows an example of such a relationship. The equation was developed based on the assumption that the glass transition depends on concentration of active groups in polymer, capable of forming labile junctions of space network. The increase in polymer modulus on cooling can be interpreted as an increase in density of labile physical bonds network. The attaimnent of certain concentration of junctions in this... 

For example, fragrance molecules were incorporated into a star polymer with nonpolar PCL arms that were polymerized via ROP of CL onto an hb poly(ester amide) as the core molecule." These star polymers formed inverse unimolecular micelles and were able to transport polar dyes from an aqueous phase to the organic phase. A similar approach was presented by Haag and co-workers employing hbPEI as the core and PEG as the arms these carriers were investigated for encapsulation and transport of dyes and therapeutics or diagnostic agents. A controlled release was possible by introduction of an acid-labile junction." " " ... 

Bender JL, Corbin PS, Fraser CL, Metcalf DH, Richardson FS, Thomas IiL, Urbas AM. Site-isolated luminescent europium complexes with polyester macroUgands metal-centered heteroarm stars and nanoscale assemblies with labile block junctions. J Am Chem Soc 2002 124 8526-8527. 

Cholera toxin and E. call heat-labile toxin ADP-ribosylate the a-subunit of trimeric G-proteins (Gj) so that they are unable to hydrolyze GTP (Casey and Gilman, 1988 Neer and Claphan, 1988). As a result, the adenylate cyclase stays in a persistently active state. The toxin is taken up from the apical pole of the enterocytes, whereas the adenylate cyclase is located at the basolateral side. Since membrane glycolipids such as the toxin receptor (ganglioside GMi) tend not to cross tight junctions, it is unlikely that the toxin reaches the basolateral side by lateral diffusion. Most likely it enters the cytosol and diffuses to the target which is also located at the cytosolic side of the membrane. 

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