Bidirectional solid phase synthesis of a model oligoglycine bolaamphiphile and purification by rapid self-assembly.

We utilised a simple bidirectional (N→C and C→N) solid phase synthesis strategy entailing conventional solid phase peptide synthesis and fragment condensation with a water-soluble carbodiimide to synthesise a model anionic glycylglycine bolaamphiphile containing a suberic acid linker moiety, namely N,N'-suberoyldiglycylglycine. The synthetic suberoyldiglycylglycine was purified using its inherent ability to rapidly self-assemble in an aqueous acidic solution (0.1% trifluoroacetic acid). Monitoring of the rapid assembly process corroborated our visual observation and confirmed packing-directed self-assembly rather than non-specific aggregation or precipitation. The progress of suberoyldiglycylglycine self-assembly was observed to be via the formation of oligomers in the solution, which then self-assembled to form layered β-sheet type macrostructures. Within 24 h, nanotubes grew from these macrostructures and eventually combined to formed microtubes, which we isolated after 5-7 days.