• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2694-2698
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• 2014

A multisegmented polystyrene (PS) with pH-cleavable ester and carbamate linkages was successfully synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry). ATRP was employed to synthesize polystyrene from hydroxyl-terminated initiator using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) as the catalyst. The reaction of the resulting PS with sodium azide yielded the azido-terminated polymer. The hydroxyl group in the other end of the polymer was reacted with 4-nitrophenyl chloroformate (NPC), followed by reaction with propargylamine to produce an alkyne end group with a carbamate linkage. The PS with an alkyne group in one end and an azide group in the other end was then self-coupled in the presence of CuBr/2,2'-bipyridyl (bpy) in DMF to yield a desired multisegmented PS. Molecular weight and molecular weight distribution of the self-coupled polymer increased with time, as in the typical step-growth-type polymerization processes. Finally, we demonstrated that the ester and carbamate linkages of the multisegmented PS were hydrolyzed in the presence of HCl to yield individual PS chains.

• Animal cells and systems
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• v.1 no.2
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• pp.329-335
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• 1997

The final pattern of the skeletal muscle of a vertebrate depends on the position-specific behavior of the muscle precursor cells during early developmental process and the abdominal muscle is made of cells which migrate a relatively long distance from their original tissue, myotome of dorsal mesoderm. We report the spatia-temporal migration pattern of abdominal muscle in Xenopus laevis by in situ hybridization and immunohistological studies. Shortly after hatching tadpole stage (stage 31/32), a group of myotomal cells detaches from the lower tip of the second somite and migrates ventrally to the lower position of abdomen. At stage 34/35, a second cell group migrates away from the third somite. Total 7 myotomal cell groups migrate ventrally one by one from the second to eighth myotome along their own pathways through the cell free space located between epidermis and subepidermal layer of the abdomen. During migration, the sizes of the cell groups (abdominal muscle anlagens) are increased to several tens fold. Around stage 40 all the abdominal muscle anlagens reaches their final positions and are interconnected side by side rostrocaudally. They are also connected to other types of muscles, forming a large multisegmented abdominal muscle. Heat shock study suggests that the disruption of segmentation of somites does not block the detachment of abdominal muscle anlagen, though the treatment gave stage- and dosagedependent effects on the migration speed.